[zfs.git] / module / zfs / zfs_vnops.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/* Portions Copyright 2007 Jeremy Teo */
/* Portions Copyright 2010 Robert Milkowski */


#include <sys/types.h>
#include <sys/param.h>
#include <sys/time.h>
#include <sys/systm.h>
#include <sys/sysmacros.h>
#include <sys/resource.h>
#include <sys/vfs.h>
#include <sys/vfs_opreg.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/kmem.h>
#include <sys/taskq.h>
#include <sys/uio.h>
#include <sys/vmsystm.h>
#include <sys/atomic.h>
#include <vm/pvn.h>
#include <sys/pathname.h>
#include <sys/cmn_err.h>
#include <sys/errno.h>
#include <sys/unistd.h>
#include <sys/zfs_dir.h>
#include <sys/zfs_acl.h>
#include <sys/zfs_ioctl.h>
#include <sys/fs/zfs.h>
#include <sys/dmu.h>
#include <sys/dmu_objset.h>
#include <sys/spa.h>
#include <sys/txg.h>
#include <sys/dbuf.h>
#include <sys/zap.h>
#include <sys/sa.h>
#include <sys/dirent.h>
#include <sys/policy.h>
#include <sys/sunddi.h>
#include <sys/sid.h>
#include <sys/mode.h>
#include "fs/fs_subr.h"
#include <sys/zfs_ctldir.h>
#include <sys/zfs_fuid.h>
#include <sys/zfs_sa.h>
#include <sys/zfs_vnops.h>
#include <sys/dnlc.h>
#include <sys/zfs_rlock.h>
#include <sys/extdirent.h>
#include <sys/kidmap.h>
#include <sys/cred.h>
#include <sys/attr.h>
#include <sys/zpl.h>

/*
 * Programming rules.
 *
 * Each vnode op performs some logical unit of work.  To do this, the ZPL must
 * properly lock its in-core state, create a DMU transaction, do the work,
 * record this work in the intent log (ZIL), commit the DMU transaction,
 * and wait for the intent log to commit if it is a synchronous operation.
 * Moreover, the vnode ops must work in both normal and log replay context.
 * The ordering of events is important to avoid deadlocks and references
 * to freed memory.  The example below illustrates the following Big Rules:
 *
 *  (1) A check must be made in each zfs thread for a mounted file system.
 *      This is done avoiding races using ZFS_ENTER(zsb).
 *      A ZFS_EXIT(zsb) is needed before all returns.  Any znodes
 *      must be checked with ZFS_VERIFY_ZP(zp).  Both of these macros
 *      can return EIO from the calling function.
 *
 *  (2) iput() should always be the last thing except for zil_commit()
 *      (if necessary) and ZFS_EXIT(). This is for 3 reasons:
 *      First, if it's the last reference, the vnode/znode
 *      can be freed, so the zp may point to freed memory.  Second, the last
 *      reference will call zfs_zinactive(), which may induce a lot of work --
 *      pushing cached pages (which acquires range locks) and syncing out
 *      cached atime changes.  Third, zfs_zinactive() may require a new tx,
 *      which could deadlock the system if you were already holding one.
 *      If you must call iput() within a tx then use iput_ASYNC().
 *
 *  (3) All range locks must be grabbed before calling dmu_tx_assign(),
 *      as they can span dmu_tx_assign() calls.
 *
 *  (4) Always pass TXG_NOWAIT as the second argument to dmu_tx_assign().
 *      This is critical because we don't want to block while holding locks.
 *      Note, in particular, that if a lock is sometimes acquired before
 *      the tx assigns, and sometimes after (e.g. z_lock), then failing to
 *      use a non-blocking assign can deadlock the system.  The scenario:
 *
 *      Thread A has grabbed a lock before calling dmu_tx_assign().
 *      Thread B is in an already-assigned tx, and blocks for this lock.
 *      Thread A calls dmu_tx_assign(TXG_WAIT) and blocks in txg_wait_open()
 *      forever, because the previous txg can't quiesce until B's tx commits.
 *
 *      If dmu_tx_assign() returns ERESTART and zsb->z_assign is TXG_NOWAIT,
 *      then drop all locks, call dmu_tx_wait(), and try again.
 *
 *  (5) If the operation succeeded, generate the intent log entry for it
 *      before dropping locks.  This ensures that the ordering of events
 *      in the intent log matches the order in which they actually occurred.
 *      During ZIL replay the zfs_log_* functions will update the sequence
 *      number to indicate the zil transaction has replayed.
 *
 *  (6) At the end of each vnode op, the DMU tx must always commit,
 *      regardless of whether there were any errors.
 *
 *  (7) After dropping all locks, invoke zil_commit(zilog, foid)
 *      to ensure that synchronous semantics are provided when necessary.
 *
 * In general, this is how things should be ordered in each vnode op:
 *
 *      ZFS_ENTER(zsb);         // exit if unmounted
 * top:
 *      zfs_dirent_lock(&dl, ...)       // lock directory entry (may igrab())
 *      rw_enter(...);                  // grab any other locks you need
 *      tx = dmu_tx_create(...);        // get DMU tx
 *      dmu_tx_hold_*();                // hold each object you might modify
 *      error = dmu_tx_assign(tx, TXG_NOWAIT);  // try to assign
 *      if (error) {
 *              rw_exit(...);           // drop locks
 *              zfs_dirent_unlock(dl);  // unlock directory entry
 *              iput(...);              // release held vnodes
 *              if (error == ERESTART) {
 *                      dmu_tx_wait(tx);
 *                      dmu_tx_abort(tx);
 *                      goto top;
 *              }
 *              dmu_tx_abort(tx);       // abort DMU tx
 *              ZFS_EXIT(zsb);  // finished in zfs
 *              return (error);         // really out of space
 *      }
 *      error = do_real_work();         // do whatever this VOP does
 *      if (error == 0)
 *              zfs_log_*(...);         // on success, make ZIL entry
 *      dmu_tx_commit(tx);              // commit DMU tx -- error or not
 *      rw_exit(...);                   // drop locks
 *      zfs_dirent_unlock(dl);          // unlock directory entry
 *      iput(...);                      // release held vnodes
 *      zil_commit(zilog, foid);        // synchronous when necessary
 *      ZFS_EXIT(zsb);          // finished in zfs
 *      return (error);                 // done, report error
 */

/*
 * Virus scanning is unsupported.  It would be possible to add a hook
 * here to performance the required virus scan.  This could be done
 * entirely in the kernel or potentially as an update to invoke a
 * scanning utility.
 */
static int
zfs_vscan(struct inode *ip, cred_t *cr, int async)
{
        return (0);
}

/* ARGSUSED */
int
zfs_open(struct inode *ip, int mode, int flag, cred_t *cr)
{
        znode_t *zp = ITOZ(ip);
        zfs_sb_t *zsb = ITOZSB(ip);

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        /* Honor ZFS_APPENDONLY file attribute */
        if ((mode & FMODE_WRITE) && (zp->z_pflags & ZFS_APPENDONLY) &&
            ((flag & O_APPEND) == 0)) {
                ZFS_EXIT(zsb);
                return (EPERM);
        }

        /* Virus scan eligible files on open */
        if (!zfs_has_ctldir(zp) && zsb->z_vscan && S_ISREG(ip->i_mode) &&
            !(zp->z_pflags & ZFS_AV_QUARANTINED) && zp->z_size > 0) {
                if (zfs_vscan(ip, cr, 0) != 0) {
                        ZFS_EXIT(zsb);
                        return (EACCES);
                }
        }

        /* Keep a count of the synchronous opens in the znode */
        if (flag & O_SYNC)
                atomic_inc_32(&zp->z_sync_cnt);

        ZFS_EXIT(zsb);
        return (0);
}
EXPORT_SYMBOL(zfs_open);

/* ARGSUSED */
int
zfs_close(struct inode *ip, int flag, cred_t *cr)
{
        znode_t *zp = ITOZ(ip);
        zfs_sb_t *zsb = ITOZSB(ip);

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        /*
         * Zero the synchronous opens in the znode.  Under Linux the
         * zfs_close() hook is not symmetric with zfs_open(), it is
         * only called once when the last reference is dropped.
         */
        if (flag & O_SYNC)
                zp->z_sync_cnt = 0;

        if (!zfs_has_ctldir(zp) && zsb->z_vscan && S_ISREG(ip->i_mode) &&
            !(zp->z_pflags & ZFS_AV_QUARANTINED) && zp->z_size > 0)
                VERIFY(zfs_vscan(ip, cr, 1) == 0);

        ZFS_EXIT(zsb);
        return (0);
}
EXPORT_SYMBOL(zfs_close);

#if defined(_KERNEL)
/*
 * When a file is memory mapped, we must keep the IO data synchronized
 * between the DMU cache and the memory mapped pages.  What this means:
 *
 * On Write:    If we find a memory mapped page, we write to *both*
 *              the page and the dmu buffer.
 */
static void
update_pages(struct inode *ip, int64_t start, int len,
    objset_t *os, uint64_t oid)
{
        struct address_space *mp = ip->i_mapping;
        struct page *pp;
        uint64_t nbytes;
        int64_t off;
        void *pb;

        off = start & (PAGE_CACHE_SIZE-1);
        for (start &= PAGE_CACHE_MASK; len > 0; start += PAGE_CACHE_SIZE) {
                nbytes = MIN(PAGE_CACHE_SIZE - off, len);

                pp = find_lock_page(mp, start >> PAGE_CACHE_SHIFT);
                if (pp) {
                        if (mapping_writably_mapped(mp))
                                flush_dcache_page(pp);

                        pb = kmap(pp);
                        (void) dmu_read(os, oid, start+off, nbytes, pb+off,
                            DMU_READ_PREFETCH);
                        kunmap(pp);

                        if (mapping_writably_mapped(mp))
                                flush_dcache_page(pp);

                        mark_page_accessed(pp);
                        SetPageUptodate(pp);
                        ClearPageError(pp);
                        unlock_page(pp);
                        page_cache_release(pp);
                }

                len -= nbytes;
                off = 0;
        }
}

/*
 * When a file is memory mapped, we must keep the IO data synchronized
 * between the DMU cache and the memory mapped pages.  What this means:
 *
 * On Read:     We "read" preferentially from memory mapped pages,
 *              else we default from the dmu buffer.
 *
 * NOTE: We will always "break up" the IO into PAGESIZE uiomoves when
 *      the file is memory mapped.
 */
static int
mappedread(struct inode *ip, int nbytes, uio_t *uio)
{
        struct address_space *mp = ip->i_mapping;
        struct page *pp;
        znode_t *zp = ITOZ(ip);
        objset_t *os = ITOZSB(ip)->z_os;
        int64_t start, off;
        uint64_t bytes;
        int len = nbytes;
        int error = 0;
        void *pb;

        start = uio->uio_loffset;
        off = start & (PAGE_CACHE_SIZE-1);
        for (start &= PAGE_CACHE_MASK; len > 0; start += PAGE_CACHE_SIZE) {
                bytes = MIN(PAGE_CACHE_SIZE - off, len);

                pp = find_lock_page(mp, start >> PAGE_CACHE_SHIFT);
                if (pp) {
                        ASSERT(PageUptodate(pp));

                        pb = kmap(pp);
                        error = uiomove(pb + off, bytes, UIO_READ, uio);
                        kunmap(pp);

                        if (mapping_writably_mapped(mp))
                                flush_dcache_page(pp);

                        mark_page_accessed(pp);
                        unlock_page(pp);
                        page_cache_release(pp);
                } else {
                        error = dmu_read_uio(os, zp->z_id, uio, bytes);
                }

                len -= bytes;
                off = 0;
                if (error)
                        break;
        }
        return (error);
}
#endif /* _KERNEL */

unsigned long zfs_read_chunk_size = 1024 * 1024; /* Tunable */

/*
 * Read bytes from specified file into supplied buffer.
 *
 *      IN:     ip      - inode of file to be read from.
 *              uio     - structure supplying read location, range info,
 *                        and return buffer.
 *              ioflag  - FSYNC flags; used to provide FRSYNC semantics.
 *                        O_DIRECT flag; used to bypass page cache.
 *              cr      - credentials of caller.
 *
 *      OUT:    uio     - updated offset and range, buffer filled.
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Side Effects:
 *      inode - atime updated if byte count > 0
 */
/* ARGSUSED */
int
zfs_read(struct inode *ip, uio_t *uio, int ioflag, cred_t *cr)
{
        znode_t         *zp = ITOZ(ip);
        zfs_sb_t        *zsb = ITOZSB(ip);
        objset_t        *os;
        ssize_t         n, nbytes;
        int             error = 0;
        rl_t            *rl;
#ifdef HAVE_UIO_ZEROCOPY
        xuio_t          *xuio = NULL;
#endif /* HAVE_UIO_ZEROCOPY */

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);
        os = zsb->z_os;

        if (zp->z_pflags & ZFS_AV_QUARANTINED) {
                ZFS_EXIT(zsb);
                return (EACCES);
        }

        /*
         * Validate file offset
         */
        if (uio->uio_loffset < (offset_t)0) {
                ZFS_EXIT(zsb);
                return (EINVAL);
        }

        /*
         * Fasttrack empty reads
         */
        if (uio->uio_resid == 0) {
                ZFS_EXIT(zsb);
                return (0);
        }

        /*
         * Check for mandatory locks
         */
        if (mandatory_lock(ip) &&
            !lock_may_read(ip, uio->uio_loffset, uio->uio_resid)) {
                ZFS_EXIT(zsb);
                return (EAGAIN);
        }

        /*
         * If we're in FRSYNC mode, sync out this znode before reading it.
         */
        if (ioflag & FRSYNC || zsb->z_os->os_sync == ZFS_SYNC_ALWAYS)
                zil_commit(zsb->z_log, zp->z_id);

        /*
         * Lock the range against changes.
         */
        rl = zfs_range_lock(zp, uio->uio_loffset, uio->uio_resid, RL_READER);

        /*
         * If we are reading past end-of-file we can skip
         * to the end; but we might still need to set atime.
         */
        if (uio->uio_loffset >= zp->z_size) {
                error = 0;
                goto out;
        }

        ASSERT(uio->uio_loffset < zp->z_size);
        n = MIN(uio->uio_resid, zp->z_size - uio->uio_loffset);

#ifdef HAVE_UIO_ZEROCOPY
        if ((uio->uio_extflg == UIO_XUIO) &&
            (((xuio_t *)uio)->xu_type == UIOTYPE_ZEROCOPY)) {
                int nblk;
                int blksz = zp->z_blksz;
                uint64_t offset = uio->uio_loffset;

                xuio = (xuio_t *)uio;
                if ((ISP2(blksz))) {
                        nblk = (P2ROUNDUP(offset + n, blksz) - P2ALIGN(offset,
                            blksz)) / blksz;
                } else {
                        ASSERT(offset + n <= blksz);
                        nblk = 1;
                }
                (void) dmu_xuio_init(xuio, nblk);

                if (vn_has_cached_data(ip)) {
                        /*
                         * For simplicity, we always allocate a full buffer
                         * even if we only expect to read a portion of a block.
                         */
                        while (--nblk >= 0) {
                                (void) dmu_xuio_add(xuio,
                                    dmu_request_arcbuf(sa_get_db(zp->z_sa_hdl),
                                    blksz), 0, blksz);
                        }
                }
        }
#endif /* HAVE_UIO_ZEROCOPY */

        while (n > 0) {
                nbytes = MIN(n, zfs_read_chunk_size -
                    P2PHASE(uio->uio_loffset, zfs_read_chunk_size));

                if (zp->z_is_mapped && !(ioflag & O_DIRECT))
                        error = mappedread(ip, nbytes, uio);
                else
                        error = dmu_read_uio(os, zp->z_id, uio, nbytes);

                if (error) {
                        /* convert checksum errors into IO errors */
                        if (error == ECKSUM)
                                error = EIO;
                        break;
                }

                n -= nbytes;
        }
out:
        zfs_range_unlock(rl);

        ZFS_ACCESSTIME_STAMP(zsb, zp);
        zfs_inode_update(zp);
        ZFS_EXIT(zsb);
        return (error);
}
EXPORT_SYMBOL(zfs_read);

/*
 * Write the bytes to a file.
 *
 *      IN:     ip      - inode of file to be written to.
 *              uio     - structure supplying write location, range info,
 *                        and data buffer.
 *              ioflag  - FAPPEND flag set if in append mode.
 *                        O_DIRECT flag; used to bypass page cache.
 *              cr      - credentials of caller.
 *
 *      OUT:    uio     - updated offset and range.
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      ip - ctime|mtime updated if byte count > 0
 */

/* ARGSUSED */
int
zfs_write(struct inode *ip, uio_t *uio, int ioflag, cred_t *cr)
{
        znode_t         *zp = ITOZ(ip);
        rlim64_t        limit = uio->uio_limit;
        ssize_t         start_resid = uio->uio_resid;
        ssize_t         tx_bytes;
        uint64_t        end_size;
        dmu_tx_t        *tx;
        zfs_sb_t        *zsb = ZTOZSB(zp);
        zilog_t         *zilog;
        offset_t        woff;
        ssize_t         n, nbytes;
        rl_t            *rl;
        int             max_blksz = zsb->z_max_blksz;
        int             error = 0;
        arc_buf_t       *abuf;
        iovec_t         *aiov = NULL;
        xuio_t          *xuio = NULL;
        int             i_iov = 0;
        iovec_t         *iovp = uio->uio_iov;
        int             write_eof;
        int             count = 0;
        sa_bulk_attr_t  bulk[4];
        uint64_t        mtime[2], ctime[2];
        ASSERTV(int     iovcnt = uio->uio_iovcnt);

        /*
         * Fasttrack empty write
         */
        n = start_resid;
        if (n == 0)
                return (0);

        if (limit == RLIM64_INFINITY || limit > MAXOFFSET_T)
                limit = MAXOFFSET_T;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_MTIME(zsb), NULL, &mtime, 16);
        SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_CTIME(zsb), NULL, &ctime, 16);
        SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_SIZE(zsb), NULL, &zp->z_size, 8);
        SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_FLAGS(zsb), NULL,
            &zp->z_pflags, 8);

        /*
         * If immutable or not appending then return EPERM
         */
        if ((zp->z_pflags & (ZFS_IMMUTABLE | ZFS_READONLY)) ||
            ((zp->z_pflags & ZFS_APPENDONLY) && !(ioflag & FAPPEND) &&
            (uio->uio_loffset < zp->z_size))) {
                ZFS_EXIT(zsb);
                return (EPERM);
        }

        zilog = zsb->z_log;

        /*
         * Validate file offset
         */
        woff = ioflag & FAPPEND ? zp->z_size : uio->uio_loffset;
        if (woff < 0) {
                ZFS_EXIT(zsb);
                return (EINVAL);
        }

        /*
         * Check for mandatory locks before calling zfs_range_lock()
         * in order to prevent a deadlock with locks set via fcntl().
         */
        if (mandatory_lock(ip) && !lock_may_write(ip, woff, n)) {
                ZFS_EXIT(zsb);
                return (EAGAIN);
        }

#ifdef HAVE_UIO_ZEROCOPY
        /*
         * Pre-fault the pages to ensure slow (eg NFS) pages
         * don't hold up txg.
         * Skip this if uio contains loaned arc_buf.
         */
        if ((uio->uio_extflg == UIO_XUIO) &&
            (((xuio_t *)uio)->xu_type == UIOTYPE_ZEROCOPY))
                xuio = (xuio_t *)uio;
        else
                uio_prefaultpages(MIN(n, max_blksz), uio);
#endif /* HAVE_UIO_ZEROCOPY */

        /*
         * If in append mode, set the io offset pointer to eof.
         */
        if (ioflag & FAPPEND) {
                /*
                 * Obtain an appending range lock to guarantee file append
                 * semantics.  We reset the write offset once we have the lock.
                 */
                rl = zfs_range_lock(zp, 0, n, RL_APPEND);
                woff = rl->r_off;
                if (rl->r_len == UINT64_MAX) {
                        /*
                         * We overlocked the file because this write will cause
                         * the file block size to increase.
                         * Note that zp_size cannot change with this lock held.
                         */
                        woff = zp->z_size;
                }
                uio->uio_loffset = woff;
        } else {
                /*
                 * Note that if the file block size will change as a result of
                 * this write, then this range lock will lock the entire file
                 * so that we can re-write the block safely.
                 */
                rl = zfs_range_lock(zp, woff, n, RL_WRITER);
        }

        if (woff >= limit) {
                zfs_range_unlock(rl);
                ZFS_EXIT(zsb);
                return (EFBIG);
        }

        if ((woff + n) > limit || woff > (limit - n))
                n = limit - woff;

        /* Will this write extend the file length? */
        write_eof = (woff + n > zp->z_size);

        end_size = MAX(zp->z_size, woff + n);

        /*
         * Write the file in reasonable size chunks.  Each chunk is written
         * in a separate transaction; this keeps the intent log records small
         * and allows us to do more fine-grained space accounting.
         */
        while (n > 0) {
                abuf = NULL;
                woff = uio->uio_loffset;
again:
                if (zfs_owner_overquota(zsb, zp, B_FALSE) ||
                    zfs_owner_overquota(zsb, zp, B_TRUE)) {
                        if (abuf != NULL)
                                dmu_return_arcbuf(abuf);
                        error = EDQUOT;
                        break;
                }

                if (xuio && abuf == NULL) {
                        ASSERT(i_iov < iovcnt);
                        aiov = &iovp[i_iov];
                        abuf = dmu_xuio_arcbuf(xuio, i_iov);
                        dmu_xuio_clear(xuio, i_iov);
                        ASSERT((aiov->iov_base == abuf->b_data) ||
                            ((char *)aiov->iov_base - (char *)abuf->b_data +
                            aiov->iov_len == arc_buf_size(abuf)));
                        i_iov++;
                } else if (abuf == NULL && n >= max_blksz &&
                    woff >= zp->z_size &&
                    P2PHASE(woff, max_blksz) == 0 &&
                    zp->z_blksz == max_blksz) {
                        /*
                         * This write covers a full block.  "Borrow" a buffer
                         * from the dmu so that we can fill it before we enter
                         * a transaction.  This avoids the possibility of
                         * holding up the transaction if the data copy hangs
                         * up on a pagefault (e.g., from an NFS server mapping).
                         */
                        size_t cbytes;

                        abuf = dmu_request_arcbuf(sa_get_db(zp->z_sa_hdl),
                            max_blksz);
                        ASSERT(abuf != NULL);
                        ASSERT(arc_buf_size(abuf) == max_blksz);
                        if ((error = uiocopy(abuf->b_data, max_blksz,
                            UIO_WRITE, uio, &cbytes))) {
                                dmu_return_arcbuf(abuf);
                                break;
                        }
                        ASSERT(cbytes == max_blksz);
                }

                /*
                 * Start a transaction.
                 */
                tx = dmu_tx_create(zsb->z_os);
                dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_FALSE);
                dmu_tx_hold_write(tx, zp->z_id, woff, MIN(n, max_blksz));
                zfs_sa_upgrade_txholds(tx, zp);
                error = dmu_tx_assign(tx, TXG_NOWAIT);
                if (error) {
                        if (error == ERESTART) {
                                dmu_tx_wait(tx);
                                dmu_tx_abort(tx);
                                goto again;
                        }
                        dmu_tx_abort(tx);
                        if (abuf != NULL)
                                dmu_return_arcbuf(abuf);
                        break;
                }

                /*
                 * If zfs_range_lock() over-locked we grow the blocksize
                 * and then reduce the lock range.  This will only happen
                 * on the first iteration since zfs_range_reduce() will
                 * shrink down r_len to the appropriate size.
                 */
                if (rl->r_len == UINT64_MAX) {
                        uint64_t new_blksz;

                        if (zp->z_blksz > max_blksz) {
                                ASSERT(!ISP2(zp->z_blksz));
                                new_blksz = MIN(end_size, SPA_MAXBLOCKSIZE);
                        } else {
                                new_blksz = MIN(end_size, max_blksz);
                        }
                        zfs_grow_blocksize(zp, new_blksz, tx);
                        zfs_range_reduce(rl, woff, n);
                }

                /*
                 * XXX - should we really limit each write to z_max_blksz?
                 * Perhaps we should use SPA_MAXBLOCKSIZE chunks?
                 */
                nbytes = MIN(n, max_blksz - P2PHASE(woff, max_blksz));

                if (abuf == NULL) {
                        tx_bytes = uio->uio_resid;
                        error = dmu_write_uio_dbuf(sa_get_db(zp->z_sa_hdl),
                            uio, nbytes, tx);
                        tx_bytes -= uio->uio_resid;
                } else {
                        tx_bytes = nbytes;
                        ASSERT(xuio == NULL || tx_bytes == aiov->iov_len);
                        /*
                         * If this is not a full block write, but we are
                         * extending the file past EOF and this data starts
                         * block-aligned, use assign_arcbuf().  Otherwise,
                         * write via dmu_write().
                         */
                        if (tx_bytes < max_blksz && (!write_eof ||
                            aiov->iov_base != abuf->b_data)) {
                                ASSERT(xuio);
                                dmu_write(zsb->z_os, zp->z_id, woff,
                                    aiov->iov_len, aiov->iov_base, tx);
                                dmu_return_arcbuf(abuf);
                                xuio_stat_wbuf_copied();
                        } else {
                                ASSERT(xuio || tx_bytes == max_blksz);
                                dmu_assign_arcbuf(sa_get_db(zp->z_sa_hdl),
                                    woff, abuf, tx);
                        }
                        ASSERT(tx_bytes <= uio->uio_resid);
                        uioskip(uio, tx_bytes);
                }

                if (tx_bytes && zp->z_is_mapped && !(ioflag & O_DIRECT))
                        update_pages(ip, woff, tx_bytes, zsb->z_os, zp->z_id);

                /*
                 * If we made no progress, we're done.  If we made even
                 * partial progress, update the znode and ZIL accordingly.
                 */
                if (tx_bytes == 0) {
                        (void) sa_update(zp->z_sa_hdl, SA_ZPL_SIZE(zsb),
                            (void *)&zp->z_size, sizeof (uint64_t), tx);
                        dmu_tx_commit(tx);
                        ASSERT(error != 0);
                        break;
                }

                /*
                 * Clear Set-UID/Set-GID bits on successful write if not
                 * privileged and at least one of the excute bits is set.
                 *
                 * It would be nice to to this after all writes have
                 * been done, but that would still expose the ISUID/ISGID
                 * to another app after the partial write is committed.
                 *
                 * Note: we don't call zfs_fuid_map_id() here because
                 * user 0 is not an ephemeral uid.
                 */
                mutex_enter(&zp->z_acl_lock);
                if ((zp->z_mode & (S_IXUSR | (S_IXUSR >> 3) |
                    (S_IXUSR >> 6))) != 0 &&
                    (zp->z_mode & (S_ISUID | S_ISGID)) != 0 &&
                    secpolicy_vnode_setid_retain(cr,
                    (zp->z_mode & S_ISUID) != 0 && zp->z_uid == 0) != 0) {
                        uint64_t newmode;
                        zp->z_mode &= ~(S_ISUID | S_ISGID);
                        newmode = zp->z_mode;
                        (void) sa_update(zp->z_sa_hdl, SA_ZPL_MODE(zsb),
                            (void *)&newmode, sizeof (uint64_t), tx);
                }
                mutex_exit(&zp->z_acl_lock);

                zfs_tstamp_update_setup(zp, CONTENT_MODIFIED, mtime, ctime,
                    B_TRUE);

                /*
                 * Update the file size (zp_size) if it has changed;
                 * account for possible concurrent updates.
                 */
                while ((end_size = zp->z_size) < uio->uio_loffset) {
                        (void) atomic_cas_64(&zp->z_size, end_size,
                            uio->uio_loffset);
                        ASSERT(error == 0);
                }
                /*
                 * If we are replaying and eof is non zero then force
                 * the file size to the specified eof. Note, there's no
                 * concurrency during replay.
                 */
                if (zsb->z_replay && zsb->z_replay_eof != 0)
                        zp->z_size = zsb->z_replay_eof;

                error = sa_bulk_update(zp->z_sa_hdl, bulk, count, tx);

                zfs_log_write(zilog, tx, TX_WRITE, zp, woff, tx_bytes, ioflag);
                dmu_tx_commit(tx);

                if (error != 0)
                        break;
                ASSERT(tx_bytes == nbytes);
                n -= nbytes;

                if (!xuio && n > 0)
                        uio_prefaultpages(MIN(n, max_blksz), uio);
        }

        zfs_range_unlock(rl);

        /*
         * If we're in replay mode, or we made no progress, return error.
         * Otherwise, it's at least a partial write, so it's successful.
         */
        if (zsb->z_replay || uio->uio_resid == start_resid) {
                ZFS_EXIT(zsb);
                return (error);
        }

        if (ioflag & (FSYNC | FDSYNC) ||
            zsb->z_os->os_sync == ZFS_SYNC_ALWAYS)
                zil_commit(zilog, zp->z_id);

        zfs_inode_update(zp);
        ZFS_EXIT(zsb);
        return (0);
}
EXPORT_SYMBOL(zfs_write);

static void
iput_async(struct inode *ip, taskq_t *taskq)
{
        ASSERT(atomic_read(&ip->i_count) > 0);
        if (atomic_read(&ip->i_count) == 1)
                taskq_dispatch(taskq, (task_func_t *)iput, ip, TQ_PUSHPAGE);
        else
                iput(ip);
}

void
zfs_get_done(zgd_t *zgd, int error)
{
        znode_t *zp = zgd->zgd_private;
        objset_t *os = ZTOZSB(zp)->z_os;

        if (zgd->zgd_db)
                dmu_buf_rele(zgd->zgd_db, zgd);

        zfs_range_unlock(zgd->zgd_rl);

        /*
         * Release the vnode asynchronously as we currently have the
         * txg stopped from syncing.
         */
        iput_async(ZTOI(zp), dsl_pool_iput_taskq(dmu_objset_pool(os)));

        if (error == 0 && zgd->zgd_bp)
                zil_add_block(zgd->zgd_zilog, zgd->zgd_bp);

        kmem_free(zgd, sizeof (zgd_t));
}

#ifdef DEBUG
static int zil_fault_io = 0;
#endif

/*
 * Get data to generate a TX_WRITE intent log record.
 */
int
zfs_get_data(void *arg, lr_write_t *lr, char *buf, zio_t *zio)
{
        zfs_sb_t *zsb = arg;
        objset_t *os = zsb->z_os;
        znode_t *zp;
        uint64_t object = lr->lr_foid;
        uint64_t offset = lr->lr_offset;
        uint64_t size = lr->lr_length;
        blkptr_t *bp = &lr->lr_blkptr;
        dmu_buf_t *db;
        zgd_t *zgd;
        int error = 0;

        ASSERT(zio != NULL);
        ASSERT(size != 0);

        /*
         * Nothing to do if the file has been removed
         */
        if (zfs_zget(zsb, object, &zp) != 0)
                return (ENOENT);
        if (zp->z_unlinked) {
                /*
                 * Release the vnode asynchronously as we currently have the
                 * txg stopped from syncing.
                 */
                iput_async(ZTOI(zp), dsl_pool_iput_taskq(dmu_objset_pool(os)));
                return (ENOENT);
        }

        zgd = (zgd_t *)kmem_zalloc(sizeof (zgd_t), KM_PUSHPAGE);
        zgd->zgd_zilog = zsb->z_log;
        zgd->zgd_private = zp;

        /*
         * Write records come in two flavors: immediate and indirect.
         * For small writes it's cheaper to store the data with the
         * log record (immediate); for large writes it's cheaper to
         * sync the data and get a pointer to it (indirect) so that
         * we don't have to write the data twice.
         */
        if (buf != NULL) { /* immediate write */
                zgd->zgd_rl = zfs_range_lock(zp, offset, size, RL_READER);
                /* test for truncation needs to be done while range locked */
                if (offset >= zp->z_size) {
                        error = ENOENT;
                } else {
                        error = dmu_read(os, object, offset, size, buf,
                            DMU_READ_NO_PREFETCH);
                }
                ASSERT(error == 0 || error == ENOENT);
        } else { /* indirect write */
                /*
                 * Have to lock the whole block to ensure when it's
                 * written out and it's checksum is being calculated
                 * that no one can change the data. We need to re-check
                 * blocksize after we get the lock in case it's changed!
                 */
                for (;;) {
                        uint64_t blkoff;
                        size = zp->z_blksz;
                        blkoff = ISP2(size) ? P2PHASE(offset, size) : offset;
                        offset -= blkoff;
                        zgd->zgd_rl = zfs_range_lock(zp, offset, size,
                            RL_READER);
                        if (zp->z_blksz == size)
                                break;
                        offset += blkoff;
                        zfs_range_unlock(zgd->zgd_rl);
                }
                /* test for truncation needs to be done while range locked */
                if (lr->lr_offset >= zp->z_size)
                        error = ENOENT;
#ifdef DEBUG
                if (zil_fault_io) {
                        error = EIO;
                        zil_fault_io = 0;
                }
#endif
                if (error == 0)
                        error = dmu_buf_hold(os, object, offset, zgd, &db,
                            DMU_READ_NO_PREFETCH);

                if (error == 0) {
                        zgd->zgd_db = db;
                        zgd->zgd_bp = bp;

                        ASSERT(db->db_offset == offset);
                        ASSERT(db->db_size == size);

                        error = dmu_sync(zio, lr->lr_common.lrc_txg,
                            zfs_get_done, zgd);
                        ASSERT(error || lr->lr_length <= zp->z_blksz);

                        /*
                         * On success, we need to wait for the write I/O
                         * initiated by dmu_sync() to complete before we can
                         * release this dbuf.  We will finish everything up
                         * in the zfs_get_done() callback.
                         */
                        if (error == 0)
                                return (0);

                        if (error == EALREADY) {
                                lr->lr_common.lrc_txtype = TX_WRITE2;
                                error = 0;
                        }
                }
        }

        zfs_get_done(zgd, error);

        return (error);
}

/*ARGSUSED*/
int
zfs_access(struct inode *ip, int mode, int flag, cred_t *cr)
{
        znode_t *zp = ITOZ(ip);
        zfs_sb_t *zsb = ITOZSB(ip);
        int error;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        if (flag & V_ACE_MASK)
                error = zfs_zaccess(zp, mode, flag, B_FALSE, cr);
        else
                error = zfs_zaccess_rwx(zp, mode, flag, cr);

        ZFS_EXIT(zsb);
        return (error);
}
EXPORT_SYMBOL(zfs_access);

/*
 * Lookup an entry in a directory, or an extended attribute directory.
 * If it exists, return a held inode reference for it.
 *
 *      IN:     dip     - inode of directory to search.
 *              nm      - name of entry to lookup.
 *              flags   - LOOKUP_XATTR set if looking for an attribute.
 *              cr      - credentials of caller.
 *              direntflags - directory lookup flags
 *              realpnp - returned pathname.
 *
 *      OUT:    ipp     - inode of located entry, NULL if not found.
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      NA
 */
/* ARGSUSED */
int
zfs_lookup(struct inode *dip, char *nm, struct inode **ipp, int flags,
    cred_t *cr, int *direntflags, pathname_t *realpnp)
{
        znode_t *zdp = ITOZ(dip);
        zfs_sb_t *zsb = ITOZSB(dip);
        int error = 0;

        /* fast path */
        if (!(flags & (LOOKUP_XATTR | FIGNORECASE))) {

                if (!S_ISDIR(dip->i_mode)) {
                        return (ENOTDIR);
                } else if (zdp->z_sa_hdl == NULL) {
                        return (EIO);
                }

                if (nm[0] == 0 || (nm[0] == '.' && nm[1] == '\0')) {
                        error = zfs_fastaccesschk_execute(zdp, cr);
                        if (!error) {
                                *ipp = dip;
                                igrab(*ipp);
                                return (0);
                        }
                        return (error);
#ifdef HAVE_DNLC
                } else {
                        vnode_t *tvp = dnlc_lookup(dvp, nm);

                        if (tvp) {
                                error = zfs_fastaccesschk_execute(zdp, cr);
                                if (error) {
                                        iput(tvp);
                                        return (error);
                                }
                                if (tvp == DNLC_NO_VNODE) {
                                        iput(tvp);
                                        return (ENOENT);
                                } else {
                                        *vpp = tvp;
                                        return (specvp_check(vpp, cr));
                                }
                        }
#endif /* HAVE_DNLC */
                }
        }

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zdp);

        *ipp = NULL;

        if (flags & LOOKUP_XATTR) {
                /*
                 * We don't allow recursive attributes..
                 * Maybe someday we will.
                 */
                if (zdp->z_pflags & ZFS_XATTR) {
                        ZFS_EXIT(zsb);
                        return (EINVAL);
                }

                if ((error = zfs_get_xattrdir(zdp, ipp, cr, flags))) {
                        ZFS_EXIT(zsb);
                        return (error);
                }

                /*
                 * Do we have permission to get into attribute directory?
                 */

                if ((error = zfs_zaccess(ITOZ(*ipp), ACE_EXECUTE, 0,
                    B_FALSE, cr))) {
                        iput(*ipp);
                        *ipp = NULL;
                }

                ZFS_EXIT(zsb);
                return (error);
        }

        if (!S_ISDIR(dip->i_mode)) {
                ZFS_EXIT(zsb);
                return (ENOTDIR);
        }

        /*
         * Check accessibility of directory.
         */

        if ((error = zfs_zaccess(zdp, ACE_EXECUTE, 0, B_FALSE, cr))) {
                ZFS_EXIT(zsb);
                return (error);
        }

        if (zsb->z_utf8 && u8_validate(nm, strlen(nm),
            NULL, U8_VALIDATE_ENTIRE, &error) < 0) {
                ZFS_EXIT(zsb);
                return (EILSEQ);
        }

        error = zfs_dirlook(zdp, nm, ipp, flags, direntflags, realpnp);
        if ((error == 0) && (*ipp))
                zfs_inode_update(ITOZ(*ipp));

        ZFS_EXIT(zsb);
        return (error);
}
EXPORT_SYMBOL(zfs_lookup);

/*
 * Attempt to create a new entry in a directory.  If the entry
 * already exists, truncate the file if permissible, else return
 * an error.  Return the ip of the created or trunc'd file.
 *
 *      IN:     dip     - inode of directory to put new file entry in.
 *              name    - name of new file entry.
 *              vap     - attributes of new file.
 *              excl    - flag indicating exclusive or non-exclusive mode.
 *              mode    - mode to open file with.
 *              cr      - credentials of caller.
 *              flag    - large file flag [UNUSED].
 *              vsecp   - ACL to be set
 *
 *      OUT:    ipp     - inode of created or trunc'd entry.
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      dip - ctime|mtime updated if new entry created
 *       ip - ctime|mtime always, atime if new
 */

/* ARGSUSED */
int
zfs_create(struct inode *dip, char *name, vattr_t *vap, int excl,
    int mode, struct inode **ipp, cred_t *cr, int flag, vsecattr_t *vsecp)
{
        znode_t         *zp, *dzp = ITOZ(dip);
        zfs_sb_t        *zsb = ITOZSB(dip);
        zilog_t         *zilog;
        objset_t        *os;
        zfs_dirlock_t   *dl;
        dmu_tx_t        *tx;
        int             error;
        uid_t           uid;
        gid_t           gid;
        zfs_acl_ids_t   acl_ids;
        boolean_t       fuid_dirtied;
        boolean_t       have_acl = B_FALSE;

        /*
         * If we have an ephemeral id, ACL, or XVATTR then
         * make sure file system is at proper version
         */

        gid = crgetgid(cr);
        uid = crgetuid(cr);

        if (zsb->z_use_fuids == B_FALSE &&
            (vsecp || IS_EPHEMERAL(uid) || IS_EPHEMERAL(gid)))
                return (EINVAL);

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(dzp);
        os = zsb->z_os;
        zilog = zsb->z_log;

        if (zsb->z_utf8 && u8_validate(name, strlen(name),
            NULL, U8_VALIDATE_ENTIRE, &error) < 0) {
                ZFS_EXIT(zsb);
                return (EILSEQ);
        }

        if (vap->va_mask & ATTR_XVATTR) {
                if ((error = secpolicy_xvattr((xvattr_t *)vap,
                    crgetuid(cr), cr, vap->va_mode)) != 0) {
                        ZFS_EXIT(zsb);
                        return (error);
                }
        }

top:
        *ipp = NULL;
        if (*name == '\0') {
                /*
                 * Null component name refers to the directory itself.
                 */
                igrab(dip);
                zp = dzp;
                dl = NULL;
                error = 0;
        } else {
                /* possible igrab(zp) */
                int zflg = 0;

                if (flag & FIGNORECASE)
                        zflg |= ZCILOOK;

                error = zfs_dirent_lock(&dl, dzp, name, &zp, zflg,
                    NULL, NULL);
                if (error) {
                        if (have_acl)
                                zfs_acl_ids_free(&acl_ids);
                        if (strcmp(name, "..") == 0)
                                error = EISDIR;
                        ZFS_EXIT(zsb);
                        return (error);
                }
        }

        if (zp == NULL) {
                uint64_t txtype;

                /*
                 * Create a new file object and update the directory
                 * to reference it.
                 */
                if ((error = zfs_zaccess(dzp, ACE_ADD_FILE, 0, B_FALSE, cr))) {
                        if (have_acl)
                                zfs_acl_ids_free(&acl_ids);
                        goto out;
                }

                /*
                 * We only support the creation of regular files in
                 * extended attribute directories.
                 */

                if ((dzp->z_pflags & ZFS_XATTR) && !S_ISREG(vap->va_mode)) {
                        if (have_acl)
                                zfs_acl_ids_free(&acl_ids);
                        error = EINVAL;
                        goto out;
                }

                if (!have_acl && (error = zfs_acl_ids_create(dzp, 0, vap,
                    cr, vsecp, &acl_ids)) != 0)
                        goto out;
                have_acl = B_TRUE;

                if (zfs_acl_ids_overquota(zsb, &acl_ids)) {
                        zfs_acl_ids_free(&acl_ids);
                        error = EDQUOT;
                        goto out;
                }

                tx = dmu_tx_create(os);

                dmu_tx_hold_sa_create(tx, acl_ids.z_aclp->z_acl_bytes +
                    ZFS_SA_BASE_ATTR_SIZE);

                fuid_dirtied = zsb->z_fuid_dirty;
                if (fuid_dirtied)
                        zfs_fuid_txhold(zsb, tx);
                dmu_tx_hold_zap(tx, dzp->z_id, TRUE, name);
                dmu_tx_hold_sa(tx, dzp->z_sa_hdl, B_FALSE);
                if (!zsb->z_use_sa &&
                    acl_ids.z_aclp->z_acl_bytes > ZFS_ACE_SPACE) {
                        dmu_tx_hold_write(tx, DMU_NEW_OBJECT,
                            0, acl_ids.z_aclp->z_acl_bytes);
                }
                error = dmu_tx_assign(tx, TXG_NOWAIT);
                if (error) {
                        zfs_dirent_unlock(dl);
                        if (error == ERESTART) {
                                dmu_tx_wait(tx);
                                dmu_tx_abort(tx);
                                goto top;
                        }
                        zfs_acl_ids_free(&acl_ids);
                        dmu_tx_abort(tx);
                        ZFS_EXIT(zsb);
                        return (error);
                }
                zfs_mknode(dzp, vap, tx, cr, 0, &zp, &acl_ids);

                if (fuid_dirtied)
                        zfs_fuid_sync(zsb, tx);

                (void) zfs_link_create(dl, zp, tx, ZNEW);
                txtype = zfs_log_create_txtype(Z_FILE, vsecp, vap);
                if (flag & FIGNORECASE)
                        txtype |= TX_CI;
                zfs_log_create(zilog, tx, txtype, dzp, zp, name,
                    vsecp, acl_ids.z_fuidp, vap);
                zfs_acl_ids_free(&acl_ids);
                dmu_tx_commit(tx);
        } else {
                int aflags = (flag & FAPPEND) ? V_APPEND : 0;

                if (have_acl)
                        zfs_acl_ids_free(&acl_ids);
                have_acl = B_FALSE;

                /*
                 * A directory entry already exists for this name.
                 */
                /*
                 * Can't truncate an existing file if in exclusive mode.
                 */
                if (excl) {
                        error = EEXIST;
                        goto out;
                }
                /*
                 * Can't open a directory for writing.
                 */
                if (S_ISDIR(ZTOI(zp)->i_mode)) {
                        error = EISDIR;
                        goto out;
                }
                /*
                 * Verify requested access to file.
                 */
                if (mode && (error = zfs_zaccess_rwx(zp, mode, aflags, cr))) {
                        goto out;
                }

                mutex_enter(&dzp->z_lock);
                dzp->z_seq++;
                mutex_exit(&dzp->z_lock);

                /*
                 * Truncate regular files if requested.
                 */
                if (S_ISREG(ZTOI(zp)->i_mode) &&
                    (vap->va_mask & ATTR_SIZE) && (vap->va_size == 0)) {
                        /* we can't hold any locks when calling zfs_freesp() */
                        zfs_dirent_unlock(dl);
                        dl = NULL;
                        error = zfs_freesp(zp, 0, 0, mode, TRUE);
                }
        }
out:

        if (dl)
                zfs_dirent_unlock(dl);

        if (error) {
                if (zp)
                        iput(ZTOI(zp));
        } else {
                zfs_inode_update(dzp);
                zfs_inode_update(zp);
                *ipp = ZTOI(zp);
        }

        if (zsb->z_os->os_sync == ZFS_SYNC_ALWAYS)
                zil_commit(zilog, 0);

        ZFS_EXIT(zsb);
        return (error);
}
EXPORT_SYMBOL(zfs_create);

/*
 * Remove an entry from a directory.
 *
 *      IN:     dip     - inode of directory to remove entry from.
 *              name    - name of entry to remove.
 *              cr      - credentials of caller.
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      dip - ctime|mtime
 *       ip - ctime (if nlink > 0)
 */

uint64_t null_xattr = 0;

/*ARGSUSED*/
int
zfs_remove(struct inode *dip, char *name, cred_t *cr)
{
        znode_t         *zp, *dzp = ITOZ(dip);
        znode_t         *xzp;
        struct inode    *ip;
        zfs_sb_t        *zsb = ITOZSB(dip);
        zilog_t         *zilog;
        uint64_t        xattr_obj;
        uint64_t        xattr_obj_unlinked = 0;
        uint64_t        obj = 0;
        zfs_dirlock_t   *dl;
        dmu_tx_t        *tx;
        boolean_t       unlinked;
        uint64_t        txtype;
        pathname_t      *realnmp = NULL;
#ifdef HAVE_PN_UTILS
        pathname_t      realnm;
#endif /* HAVE_PN_UTILS */
        int             error;
        int             zflg = ZEXISTS;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(dzp);
        zilog = zsb->z_log;

#ifdef HAVE_PN_UTILS
        if (flags & FIGNORECASE) {
                zflg |= ZCILOOK;
                pn_alloc(&realnm);
                realnmp = &realnm;
        }
#endif /* HAVE_PN_UTILS */

top:
        xattr_obj = 0;
        xzp = NULL;
        /*
         * Attempt to lock directory; fail if entry doesn't exist.
         */
        if ((error = zfs_dirent_lock(&dl, dzp, name, &zp, zflg,
            NULL, realnmp))) {
#ifdef HAVE_PN_UTILS
                if (realnmp)
                        pn_free(realnmp);
#endif /* HAVE_PN_UTILS */
                ZFS_EXIT(zsb);
                return (error);
        }

        ip = ZTOI(zp);

        if ((error = zfs_zaccess_delete(dzp, zp, cr))) {
                goto out;
        }

        /*
         * Need to use rmdir for removing directories.
         */
        if (S_ISDIR(ip->i_mode)) {
                error = EPERM;
                goto out;
        }

#ifdef HAVE_DNLC
        if (realnmp)
                dnlc_remove(dvp, realnmp->pn_buf);
        else
                dnlc_remove(dvp, name);
#endif /* HAVE_DNLC */

        /*
         * We never delete the znode and always place it in the unlinked
         * set.  The dentry cache will always hold the last reference and
         * is responsible for safely freeing the znode.
         */
        obj = zp->z_id;
        tx = dmu_tx_create(zsb->z_os);
        dmu_tx_hold_zap(tx, dzp->z_id, FALSE, name);
        dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_FALSE);
        zfs_sa_upgrade_txholds(tx, zp);
        zfs_sa_upgrade_txholds(tx, dzp);

        /* are there any extended attributes? */
        error = sa_lookup(zp->z_sa_hdl, SA_ZPL_XATTR(zsb),
            &xattr_obj, sizeof (xattr_obj));
        if (error == 0 && xattr_obj) {
                error = zfs_zget(zsb, xattr_obj, &xzp);
                ASSERT3U(error, ==, 0);
                dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_TRUE);
                dmu_tx_hold_sa(tx, xzp->z_sa_hdl, B_FALSE);
        }

        /* charge as an update -- would be nice not to charge at all */
        dmu_tx_hold_zap(tx, zsb->z_unlinkedobj, FALSE, NULL);

        error = dmu_tx_assign(tx, TXG_NOWAIT);
        if (error) {
                zfs_dirent_unlock(dl);
                iput(ip);
                if (xzp)
                        iput(ZTOI(xzp));
                if (error == ERESTART) {
                        dmu_tx_wait(tx);
                        dmu_tx_abort(tx);
                        goto top;
                }
#ifdef HAVE_PN_UTILS
                if (realnmp)
                        pn_free(realnmp);
#endif /* HAVE_PN_UTILS */
                dmu_tx_abort(tx);
                ZFS_EXIT(zsb);
                return (error);
        }

        /*
         * Remove the directory entry.
         */
        error = zfs_link_destroy(dl, zp, tx, zflg, &unlinked);

        if (error) {
                dmu_tx_commit(tx);
                goto out;
        }

        if (unlinked) {
                /*
                 * Hold z_lock so that we can make sure that the ACL obj
                 * hasn't changed.  Could have been deleted due to
                 * zfs_sa_upgrade().
                 */
                mutex_enter(&zp->z_lock);
                (void) sa_lookup(zp->z_sa_hdl, SA_ZPL_XATTR(zsb),
                    &xattr_obj_unlinked, sizeof (xattr_obj_unlinked));
                mutex_exit(&zp->z_lock);
                zfs_unlinked_add(zp, tx);
        }

        txtype = TX_REMOVE;
#ifdef HAVE_PN_UTILS
        if (flags & FIGNORECASE)
                txtype |= TX_CI;
#endif /* HAVE_PN_UTILS */
        zfs_log_remove(zilog, tx, txtype, dzp, name, obj);

        dmu_tx_commit(tx);
out:
#ifdef HAVE_PN_UTILS
        if (realnmp)
                pn_free(realnmp);
#endif /* HAVE_PN_UTILS */

        zfs_dirent_unlock(dl);
        zfs_inode_update(dzp);
        zfs_inode_update(zp);
        if (xzp)
                zfs_inode_update(xzp);

        iput(ip);
        if (xzp)
                iput(ZTOI(xzp));

        if (zsb->z_os->os_sync == ZFS_SYNC_ALWAYS)
                zil_commit(zilog, 0);

        ZFS_EXIT(zsb);
        return (error);
}
EXPORT_SYMBOL(zfs_remove);

/*
 * Create a new directory and insert it into dip using the name
 * provided.  Return a pointer to the inserted directory.
 *
 *      IN:     dip     - inode of directory to add subdir to.
 *              dirname - name of new directory.
 *              vap     - attributes of new directory.
 *              cr      - credentials of caller.
 *              vsecp   - ACL to be set
 *
 *      OUT:    ipp     - inode of created directory.
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      dip - ctime|mtime updated
 *      ipp - ctime|mtime|atime updated
 */
/*ARGSUSED*/
int
zfs_mkdir(struct inode *dip, char *dirname, vattr_t *vap, struct inode **ipp,
    cred_t *cr, int flags, vsecattr_t *vsecp)
{
        znode_t         *zp, *dzp = ITOZ(dip);
        zfs_sb_t        *zsb = ITOZSB(dip);
        zilog_t         *zilog;
        zfs_dirlock_t   *dl;
        uint64_t        txtype;
        dmu_tx_t        *tx;
        int             error;
        int             zf = ZNEW;
        uid_t           uid;
        gid_t           gid = crgetgid(cr);
        zfs_acl_ids_t   acl_ids;
        boolean_t       fuid_dirtied;

        ASSERT(S_ISDIR(vap->va_mode));

        /*
         * If we have an ephemeral id, ACL, or XVATTR then
         * make sure file system is at proper version
         */

        uid = crgetuid(cr);
        if (zsb->z_use_fuids == B_FALSE &&
            (vsecp || IS_EPHEMERAL(uid) || IS_EPHEMERAL(gid)))
                return (EINVAL);

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(dzp);
        zilog = zsb->z_log;

        if (dzp->z_pflags & ZFS_XATTR) {
                ZFS_EXIT(zsb);
                return (EINVAL);
        }

        if (zsb->z_utf8 && u8_validate(dirname,
            strlen(dirname), NULL, U8_VALIDATE_ENTIRE, &error) < 0) {
                ZFS_EXIT(zsb);
                return (EILSEQ);
        }
        if (flags & FIGNORECASE)
                zf |= ZCILOOK;

        if (vap->va_mask & ATTR_XVATTR) {
                if ((error = secpolicy_xvattr((xvattr_t *)vap,
                    crgetuid(cr), cr, vap->va_mode)) != 0) {
                        ZFS_EXIT(zsb);
                        return (error);
                }
        }

        if ((error = zfs_acl_ids_create(dzp, 0, vap, cr,
            vsecp, &acl_ids)) != 0) {
                ZFS_EXIT(zsb);
                return (error);
        }
        /*
         * First make sure the new directory doesn't exist.
         *
         * Existence is checked first to make sure we don't return
         * EACCES instead of EEXIST which can cause some applications
         * to fail.
         */
top:
        *ipp = NULL;

        if ((error = zfs_dirent_lock(&dl, dzp, dirname, &zp, zf,
            NULL, NULL))) {
                zfs_acl_ids_free(&acl_ids);
                ZFS_EXIT(zsb);
                return (error);
        }

        if ((error = zfs_zaccess(dzp, ACE_ADD_SUBDIRECTORY, 0, B_FALSE, cr))) {
                zfs_acl_ids_free(&acl_ids);
                zfs_dirent_unlock(dl);
                ZFS_EXIT(zsb);
                return (error);
        }

        if (zfs_acl_ids_overquota(zsb, &acl_ids)) {
                zfs_acl_ids_free(&acl_ids);
                zfs_dirent_unlock(dl);
                ZFS_EXIT(zsb);
                return (EDQUOT);
        }

        /*
         * Add a new entry to the directory.
         */
        tx = dmu_tx_create(zsb->z_os);
        dmu_tx_hold_zap(tx, dzp->z_id, TRUE, dirname);
        dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, FALSE, NULL);
        fuid_dirtied = zsb->z_fuid_dirty;
        if (fuid_dirtied)
                zfs_fuid_txhold(zsb, tx);
        if (!zsb->z_use_sa && acl_ids.z_aclp->z_acl_bytes > ZFS_ACE_SPACE) {
                dmu_tx_hold_write(tx, DMU_NEW_OBJECT, 0,
                    acl_ids.z_aclp->z_acl_bytes);
        }

        dmu_tx_hold_sa_create(tx, acl_ids.z_aclp->z_acl_bytes +
            ZFS_SA_BASE_ATTR_SIZE);

        error = dmu_tx_assign(tx, TXG_NOWAIT);
        if (error) {
                zfs_dirent_unlock(dl);
                if (error == ERESTART) {
                        dmu_tx_wait(tx);
                        dmu_tx_abort(tx);
                        goto top;
                }
                zfs_acl_ids_free(&acl_ids);
                dmu_tx_abort(tx);
                ZFS_EXIT(zsb);
                return (error);
        }

        /*
         * Create new node.
         */
        zfs_mknode(dzp, vap, tx, cr, 0, &zp, &acl_ids);

        if (fuid_dirtied)
                zfs_fuid_sync(zsb, tx);

        /*
         * Now put new name in parent dir.
         */
        (void) zfs_link_create(dl, zp, tx, ZNEW);

        *ipp = ZTOI(zp);

        txtype = zfs_log_create_txtype(Z_DIR, vsecp, vap);
        if (flags & FIGNORECASE)
                txtype |= TX_CI;
        zfs_log_create(zilog, tx, txtype, dzp, zp, dirname, vsecp,
            acl_ids.z_fuidp, vap);

        zfs_acl_ids_free(&acl_ids);

        dmu_tx_commit(tx);

        zfs_dirent_unlock(dl);

        if (zsb->z_os->os_sync == ZFS_SYNC_ALWAYS)
                zil_commit(zilog, 0);

        zfs_inode_update(dzp);
        zfs_inode_update(zp);
        ZFS_EXIT(zsb);
        return (0);
}
EXPORT_SYMBOL(zfs_mkdir);

/*
 * Remove a directory subdir entry.  If the current working
 * directory is the same as the subdir to be removed, the
 * remove will fail.
 *
 *      IN:     dip     - inode of directory to remove from.
 *              name    - name of directory to be removed.
 *              cwd     - inode of current working directory.
 *              cr      - credentials of caller.
 *              flags   - case flags
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      dip - ctime|mtime updated
 */
/*ARGSUSED*/
int
zfs_rmdir(struct inode *dip, char *name, struct inode *cwd, cred_t *cr,
    int flags)
{
        znode_t         *dzp = ITOZ(dip);
        znode_t         *zp;
        struct inode    *ip;
        zfs_sb_t        *zsb = ITOZSB(dip);
        zilog_t         *zilog;
        zfs_dirlock_t   *dl;
        dmu_tx_t        *tx;
        int             error;
        int             zflg = ZEXISTS;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(dzp);
        zilog = zsb->z_log;

        if (flags & FIGNORECASE)
                zflg |= ZCILOOK;
top:
        zp = NULL;

        /*
         * Attempt to lock directory; fail if entry doesn't exist.
         */
        if ((error = zfs_dirent_lock(&dl, dzp, name, &zp, zflg,
            NULL, NULL))) {
                ZFS_EXIT(zsb);
                return (error);
        }

        ip = ZTOI(zp);

        if ((error = zfs_zaccess_delete(dzp, zp, cr))) {
                goto out;
        }

        if (!S_ISDIR(ip->i_mode)) {
                error = ENOTDIR;
                goto out;
        }

        if (ip == cwd) {
                error = EINVAL;
                goto out;
        }

        /*
         * Grab a lock on the directory to make sure that noone is
         * trying to add (or lookup) entries while we are removing it.
         */
        rw_enter(&zp->z_name_lock, RW_WRITER);

        /*
         * Grab a lock on the parent pointer to make sure we play well
         * with the treewalk and directory rename code.
         */
        rw_enter(&zp->z_parent_lock, RW_WRITER);

        tx = dmu_tx_create(zsb->z_os);
        dmu_tx_hold_zap(tx, dzp->z_id, FALSE, name);
        dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_FALSE);
        dmu_tx_hold_zap(tx, zsb->z_unlinkedobj, FALSE, NULL);
        zfs_sa_upgrade_txholds(tx, zp);
        zfs_sa_upgrade_txholds(tx, dzp);
        error = dmu_tx_assign(tx, TXG_NOWAIT);
        if (error) {
                rw_exit(&zp->z_parent_lock);
                rw_exit(&zp->z_name_lock);
                zfs_dirent_unlock(dl);
                iput(ip);
                if (error == ERESTART) {
                        dmu_tx_wait(tx);
                        dmu_tx_abort(tx);
                        goto top;
                }
                dmu_tx_abort(tx);
                ZFS_EXIT(zsb);
                return (error);
        }

        error = zfs_link_destroy(dl, zp, tx, zflg, NULL);

        if (error == 0) {
                uint64_t txtype = TX_RMDIR;
                if (flags & FIGNORECASE)
                        txtype |= TX_CI;
                zfs_log_remove(zilog, tx, txtype, dzp, name, ZFS_NO_OBJECT);
        }

        dmu_tx_commit(tx);

        rw_exit(&zp->z_parent_lock);
        rw_exit(&zp->z_name_lock);
out:
        zfs_dirent_unlock(dl);

        zfs_inode_update(dzp);
        zfs_inode_update(zp);
        iput(ip);

        if (zsb->z_os->os_sync == ZFS_SYNC_ALWAYS)
                zil_commit(zilog, 0);

        ZFS_EXIT(zsb);
        return (error);
}
EXPORT_SYMBOL(zfs_rmdir);

/*
 * Read as many directory entries as will fit into the provided
 * dirent buffer from the given directory cursor position.
 *
 *      IN:     ip      - inode of directory to read.
 *              dirent  - buffer for directory entries.
 *
 *      OUT:    dirent  - filler buffer of directory entries.
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      ip - atime updated
 *
 * Note that the low 4 bits of the cookie returned by zap is always zero.
 * This allows us to use the low range for "special" directory entries:
 * We use 0 for '.', and 1 for '..'.  If this is the root of the filesystem,
 * we use the offset 2 for the '.zfs' directory.
 */
/* ARGSUSED */
int
zfs_readdir(struct inode *ip, void *dirent, filldir_t filldir,
    loff_t *pos, cred_t *cr)
{
        znode_t         *zp = ITOZ(ip);
        zfs_sb_t        *zsb = ITOZSB(ip);
        objset_t        *os;
        zap_cursor_t    zc;
        zap_attribute_t zap;
        int             outcount;
        int             error;
        uint8_t         prefetch;
        int             done = 0;
        uint64_t        parent;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        if ((error = sa_lookup(zp->z_sa_hdl, SA_ZPL_PARENT(zsb),
            &parent, sizeof (parent))) != 0)
                goto out;

        /*
         * Quit if directory has been removed (posix)
         */
        error = 0;
        if (zp->z_unlinked)
                goto out;

        os = zsb->z_os;
        prefetch = zp->z_zn_prefetch;

        /*
         * Initialize the iterator cursor.
         */
        if (*pos <= 3) {
                /*
                 * Start iteration from the beginning of the directory.
                 */
                zap_cursor_init(&zc, os, zp->z_id);
        } else {
                /*
                 * The offset is a serialized cursor.
                 */
                zap_cursor_init_serialized(&zc, os, zp->z_id, *pos);
        }

        /*
         * Transform to file-system independent format
         */
        outcount = 0;

        while (!done) {
                uint64_t objnum;
                /*
                 * Special case `.', `..', and `.zfs'.
                 */
                if (*pos == 0) {
                        (void) strcpy(zap.za_name, ".");
                        zap.za_normalization_conflict = 0;
                        objnum = zp->z_id;
                } else if (*pos == 1) {
                        (void) strcpy(zap.za_name, "..");
                        zap.za_normalization_conflict = 0;
                        objnum = parent;
                } else if (*pos == 2 && zfs_show_ctldir(zp)) {
                        (void) strcpy(zap.za_name, ZFS_CTLDIR_NAME);
                        zap.za_normalization_conflict = 0;
                        objnum = ZFSCTL_INO_ROOT;
                } else {
                        /*
                         * Grab next entry.
                         */
                        if ((error = zap_cursor_retrieve(&zc, &zap))) {
                                if (error == ENOENT)
                                        break;
                                else
                                        goto update;
                        }

                        /*
                         * Allow multiple entries provided the first entry is
                         * the object id.  Non-zpl consumers may safely make
                         * use of the additional space.
                         *
                         * XXX: This should be a feature flag for compatibility
                         */
                        if (zap.za_integer_length != 8 ||
                            zap.za_num_integers == 0) {
                                cmn_err(CE_WARN, "zap_readdir: bad directory "
                                    "entry, obj = %lld, offset = %lld, "
                                    "length = %d, num = %lld\n",
                                    (u_longlong_t)zp->z_id,
                                    (u_longlong_t)*pos,
                                    zap.za_integer_length,
                                    (u_longlong_t)zap.za_num_integers);
                                error = ENXIO;
                                goto update;
                        }

                        objnum = ZFS_DIRENT_OBJ(zap.za_first_integer);
                }
                done = filldir(dirent, zap.za_name, strlen(zap.za_name),
                               zap_cursor_serialize(&zc), objnum, 0);
                if (done) {
                        break;
                }

                /* Prefetch znode */
                if (prefetch) {
                        dmu_prefetch(os, objnum, 0, 0);
                }

                if (*pos > 2 || (*pos == 2 && !zfs_show_ctldir(zp))) {
                        zap_cursor_advance(&zc);
                        *pos = zap_cursor_serialize(&zc);
                } else {
                        (*pos)++;
                }
        }
        zp->z_zn_prefetch = B_FALSE; /* a lookup will re-enable pre-fetching */

update:
        zap_cursor_fini(&zc);
        if (error == ENOENT)
                error = 0;

        ZFS_ACCESSTIME_STAMP(zsb, zp);
        zfs_inode_update(zp);

out:
        ZFS_EXIT(zsb);

        return (error);
}
EXPORT_SYMBOL(zfs_readdir);

ulong_t zfs_fsync_sync_cnt = 4;

int
zfs_fsync(struct inode *ip, int syncflag, cred_t *cr)
{
        znode_t *zp = ITOZ(ip);
        zfs_sb_t *zsb = ITOZSB(ip);

        (void) tsd_set(zfs_fsyncer_key, (void *)zfs_fsync_sync_cnt);

        if (zsb->z_os->os_sync != ZFS_SYNC_DISABLED) {
                ZFS_ENTER(zsb);
                ZFS_VERIFY_ZP(zp);
                zil_commit(zsb->z_log, zp->z_id);
                ZFS_EXIT(zsb);
        }
        return (0);
}
EXPORT_SYMBOL(zfs_fsync);


/*
 * Get the requested file attributes and place them in the provided
 * vattr structure.
 *
 *      IN:     ip      - inode of file.
 *              vap     - va_mask identifies requested attributes.
 *                        If ATTR_XVATTR set, then optional attrs are requested
 *              flags   - ATTR_NOACLCHECK (CIFS server context)
 *              cr      - credentials of caller.
 *
 *      OUT:    vap     - attribute values.
 *
 *      RETURN: 0 (always succeeds)
 */
/* ARGSUSED */
int
zfs_getattr(struct inode *ip, vattr_t *vap, int flags, cred_t *cr)
{
        znode_t *zp = ITOZ(ip);
        zfs_sb_t *zsb = ITOZSB(ip);
        int     error = 0;
        uint64_t links;
        uint64_t mtime[2], ctime[2];
        xvattr_t *xvap = (xvattr_t *)vap;       /* vap may be an xvattr_t * */
        xoptattr_t *xoap = NULL;
        boolean_t skipaclchk = (flags & ATTR_NOACLCHECK) ? B_TRUE : B_FALSE;
        sa_bulk_attr_t bulk[2];
        int count = 0;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        zfs_fuid_map_ids(zp, cr, &vap->va_uid, &vap->va_gid);

        SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_MTIME(zsb), NULL, &mtime, 16);
        SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_CTIME(zsb), NULL, &ctime, 16);

        if ((error = sa_bulk_lookup(zp->z_sa_hdl, bulk, count)) != 0) {
                ZFS_EXIT(zsb);
                return (error);
        }

        /*
         * If ACL is trivial don't bother looking for ACE_READ_ATTRIBUTES.
         * Also, if we are the owner don't bother, since owner should
         * always be allowed to read basic attributes of file.
         */
        if (!(zp->z_pflags & ZFS_ACL_TRIVIAL) &&
            (vap->va_uid != crgetuid(cr))) {
                if ((error = zfs_zaccess(zp, ACE_READ_ATTRIBUTES, 0,
                    skipaclchk, cr))) {
                        ZFS_EXIT(zsb);
                        return (error);
                }
        }

        /*
         * Return all attributes.  It's cheaper to provide the answer
         * than to determine whether we were asked the question.
         */

        mutex_enter(&zp->z_lock);
        vap->va_type = vn_mode_to_vtype(zp->z_mode);
        vap->va_mode = zp->z_mode;
        vap->va_fsid = ZTOI(zp)->i_sb->s_dev;
        vap->va_nodeid = zp->z_id;
        if ((zp->z_id == zsb->z_root) && zfs_show_ctldir(zp))
                links = zp->z_links + 1;
        else
                links = zp->z_links;
        vap->va_nlink = MIN(links, ZFS_LINK_MAX);
        vap->va_size = i_size_read(ip);
        vap->va_rdev = ip->i_rdev;
        vap->va_seq = ip->i_generation;

        /*
         * Add in any requested optional attributes and the create time.
         * Also set the corresponding bits in the returned attribute bitmap.
         */
        if ((xoap = xva_getxoptattr(xvap)) != NULL && zsb->z_use_fuids) {
                if (XVA_ISSET_REQ(xvap, XAT_ARCHIVE)) {
                        xoap->xoa_archive =
                            ((zp->z_pflags & ZFS_ARCHIVE) != 0);
                        XVA_SET_RTN(xvap, XAT_ARCHIVE);
                }

                if (XVA_ISSET_REQ(xvap, XAT_READONLY)) {
                        xoap->xoa_readonly =
                            ((zp->z_pflags & ZFS_READONLY) != 0);
                        XVA_SET_RTN(xvap, XAT_READONLY);
                }

                if (XVA_ISSET_REQ(xvap, XAT_SYSTEM)) {
                        xoap->xoa_system =
                            ((zp->z_pflags & ZFS_SYSTEM) != 0);
                        XVA_SET_RTN(xvap, XAT_SYSTEM);
                }

                if (XVA_ISSET_REQ(xvap, XAT_HIDDEN)) {
                        xoap->xoa_hidden =
                            ((zp->z_pflags & ZFS_HIDDEN) != 0);
                        XVA_SET_RTN(xvap, XAT_HIDDEN);
                }

                if (XVA_ISSET_REQ(xvap, XAT_NOUNLINK)) {
                        xoap->xoa_nounlink =
                            ((zp->z_pflags & ZFS_NOUNLINK) != 0);
                        XVA_SET_RTN(xvap, XAT_NOUNLINK);
                }

                if (XVA_ISSET_REQ(xvap, XAT_IMMUTABLE)) {
                        xoap->xoa_immutable =
                            ((zp->z_pflags & ZFS_IMMUTABLE) != 0);
                        XVA_SET_RTN(xvap, XAT_IMMUTABLE);
                }

                if (XVA_ISSET_REQ(xvap, XAT_APPENDONLY)) {
                        xoap->xoa_appendonly =
                            ((zp->z_pflags & ZFS_APPENDONLY) != 0);
                        XVA_SET_RTN(xvap, XAT_APPENDONLY);
                }

                if (XVA_ISSET_REQ(xvap, XAT_NODUMP)) {
                        xoap->xoa_nodump =
                            ((zp->z_pflags & ZFS_NODUMP) != 0);
                        XVA_SET_RTN(xvap, XAT_NODUMP);
                }

                if (XVA_ISSET_REQ(xvap, XAT_OPAQUE)) {
                        xoap->xoa_opaque =
                            ((zp->z_pflags & ZFS_OPAQUE) != 0);
                        XVA_SET_RTN(xvap, XAT_OPAQUE);
                }

                if (XVA_ISSET_REQ(xvap, XAT_AV_QUARANTINED)) {
                        xoap->xoa_av_quarantined =
                            ((zp->z_pflags & ZFS_AV_QUARANTINED) != 0);
                        XVA_SET_RTN(xvap, XAT_AV_QUARANTINED);
                }

                if (XVA_ISSET_REQ(xvap, XAT_AV_MODIFIED)) {
                        xoap->xoa_av_modified =
                            ((zp->z_pflags & ZFS_AV_MODIFIED) != 0);
                        XVA_SET_RTN(xvap, XAT_AV_MODIFIED);
                }

                if (XVA_ISSET_REQ(xvap, XAT_AV_SCANSTAMP) &&
                    S_ISREG(ip->i_mode)) {
                        zfs_sa_get_scanstamp(zp, xvap);
                }

                if (XVA_ISSET_REQ(xvap, XAT_CREATETIME)) {
                        uint64_t times[2];

                        (void) sa_lookup(zp->z_sa_hdl, SA_ZPL_CRTIME(zsb),
                            times, sizeof (times));
                        ZFS_TIME_DECODE(&xoap->xoa_createtime, times);
                        XVA_SET_RTN(xvap, XAT_CREATETIME);
                }

                if (XVA_ISSET_REQ(xvap, XAT_REPARSE)) {
                        xoap->xoa_reparse = ((zp->z_pflags & ZFS_REPARSE) != 0);
                        XVA_SET_RTN(xvap, XAT_REPARSE);
                }
                if (XVA_ISSET_REQ(xvap, XAT_GEN)) {
                        xoap->xoa_generation = zp->z_gen;
                        XVA_SET_RTN(xvap, XAT_GEN);
                }

                if (XVA_ISSET_REQ(xvap, XAT_OFFLINE)) {
                        xoap->xoa_offline =
                            ((zp->z_pflags & ZFS_OFFLINE) != 0);
                        XVA_SET_RTN(xvap, XAT_OFFLINE);
                }

                if (XVA_ISSET_REQ(xvap, XAT_SPARSE)) {
                        xoap->xoa_sparse =
                            ((zp->z_pflags & ZFS_SPARSE) != 0);
                        XVA_SET_RTN(xvap, XAT_SPARSE);
                }
        }

        ZFS_TIME_DECODE(&vap->va_atime, zp->z_atime);
        ZFS_TIME_DECODE(&vap->va_mtime, mtime);
        ZFS_TIME_DECODE(&vap->va_ctime, ctime);

        mutex_exit(&zp->z_lock);

        sa_object_size(zp->z_sa_hdl, &vap->va_blksize, &vap->va_nblocks);

        if (zp->z_blksz == 0) {
                /*
                 * Block size hasn't been set; suggest maximal I/O transfers.
                 */
                vap->va_blksize = zsb->z_max_blksz;
        }

        ZFS_EXIT(zsb);
        return (0);
}
EXPORT_SYMBOL(zfs_getattr);

/*
 * Get the basic file attributes and place them in the provided kstat
 * structure.  The inode is assumed to be the authoritative source
 * for most of the attributes.  However, the znode currently has the
 * authoritative atime, blksize, and block count.
 *
 *      IN:     ip      - inode of file.
 *
 *      OUT:    sp      - kstat values.
 *
 *      RETURN: 0 (always succeeds)
 */
/* ARGSUSED */
int
zfs_getattr_fast(struct inode *ip, struct kstat *sp)
{
        znode_t *zp = ITOZ(ip);
        zfs_sb_t *zsb = ITOZSB(ip);

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        mutex_enter(&zp->z_lock);

        generic_fillattr(ip, sp);
        ZFS_TIME_DECODE(&sp->atime, zp->z_atime);

        sa_object_size(zp->z_sa_hdl, (uint32_t *)&sp->blksize, &sp->blocks);
        if (unlikely(zp->z_blksz == 0)) {
                /*
                 * Block size hasn't been set; suggest maximal I/O transfers.
                 */
                sp->blksize = zsb->z_max_blksz;
        }

        mutex_exit(&zp->z_lock);

        ZFS_EXIT(zsb);

        return (0);
}
EXPORT_SYMBOL(zfs_getattr_fast);

/*
 * Set the file attributes to the values contained in the
 * vattr structure.
 *
 *      IN:     ip      - inode of file to be modified.
 *              vap     - new attribute values.
 *                        If ATTR_XVATTR set, then optional attrs are being set
 *              flags   - ATTR_UTIME set if non-default time values provided.
 *                      - ATTR_NOACLCHECK (CIFS context only).
 *              cr      - credentials of caller.
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      ip - ctime updated, mtime updated if size changed.
 */
/* ARGSUSED */
int
zfs_setattr(struct inode *ip, vattr_t *vap, int flags, cred_t *cr)
{
        znode_t         *zp = ITOZ(ip);
        zfs_sb_t        *zsb = ITOZSB(ip);
        zilog_t         *zilog;
        dmu_tx_t        *tx;
        vattr_t         oldva;
        xvattr_t        *tmpxvattr;
        uint_t          mask = vap->va_mask;
        uint_t          saved_mask;
        int             trim_mask = 0;
        uint64_t        new_mode;
        uint64_t        new_uid, new_gid;
        uint64_t        xattr_obj;
        uint64_t        mtime[2], ctime[2];
        znode_t         *attrzp;
        int             need_policy = FALSE;
        int             err, err2;
        zfs_fuid_info_t *fuidp = NULL;
        xvattr_t *xvap = (xvattr_t *)vap;       /* vap may be an xvattr_t * */
        xoptattr_t      *xoap;
        zfs_acl_t       *aclp;
        boolean_t skipaclchk = (flags & ATTR_NOACLCHECK) ? B_TRUE : B_FALSE;
        boolean_t       fuid_dirtied = B_FALSE;
        sa_bulk_attr_t  *bulk, *xattr_bulk;
        int             count = 0, xattr_count = 0;

        if (mask == 0)
                return (0);

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        zilog = zsb->z_log;

        /*
         * Make sure that if we have ephemeral uid/gid or xvattr specified
         * that file system is at proper version level
         */

        if (zsb->z_use_fuids == B_FALSE &&
            (((mask & ATTR_UID) && IS_EPHEMERAL(vap->va_uid)) ||
            ((mask & ATTR_GID) && IS_EPHEMERAL(vap->va_gid)) ||
            (mask & ATTR_XVATTR))) {
                ZFS_EXIT(zsb);
                return (EINVAL);
        }

        if (mask & ATTR_SIZE && S_ISDIR(ip->i_mode)) {
                ZFS_EXIT(zsb);
                return (EISDIR);
        }

        if (mask & ATTR_SIZE && !S_ISREG(ip->i_mode) && !S_ISFIFO(ip->i_mode)) {
                ZFS_EXIT(zsb);
                return (EINVAL);
        }

        /*
         * If this is an xvattr_t, then get a pointer to the structure of
         * optional attributes.  If this is NULL, then we have a vattr_t.
         */
        xoap = xva_getxoptattr(xvap);

        tmpxvattr = kmem_alloc(sizeof(xvattr_t), KM_SLEEP);
        xva_init(tmpxvattr);

        bulk = kmem_alloc(sizeof(sa_bulk_attr_t) * 7, KM_SLEEP);
        xattr_bulk = kmem_alloc(sizeof(sa_bulk_attr_t) * 7, KM_SLEEP);

        /*
         * Immutable files can only alter immutable bit and atime
         */
        if ((zp->z_pflags & ZFS_IMMUTABLE) &&
            ((mask & (ATTR_SIZE|ATTR_UID|ATTR_GID|ATTR_MTIME|ATTR_MODE)) ||
            ((mask & ATTR_XVATTR) && XVA_ISSET_REQ(xvap, XAT_CREATETIME)))) {
                err = EPERM;
                goto out3;
        }

        if ((mask & ATTR_SIZE) && (zp->z_pflags & ZFS_READONLY)) {
                err = EPERM;
                goto out3;
        }

        /*
         * Verify timestamps doesn't overflow 32 bits.
         * ZFS can handle large timestamps, but 32bit syscalls can't
         * handle times greater than 2039.  This check should be removed
         * once large timestamps are fully supported.
         */
        if (mask & (ATTR_ATIME | ATTR_MTIME)) {
                if (((mask & ATTR_ATIME) && TIMESPEC_OVERFLOW(&vap->va_atime)) ||
                    ((mask & ATTR_MTIME) && TIMESPEC_OVERFLOW(&vap->va_mtime))) {
                        err = EOVERFLOW;
                        goto out3;
                }
        }

top:
        attrzp = NULL;
        aclp = NULL;

        /* Can this be moved to before the top label? */
        if (zfs_is_readonly(zsb)) {
                err = EROFS;
                goto out3;
        }

        /*
         * First validate permissions
         */

        if (mask & ATTR_SIZE) {
                err = zfs_zaccess(zp, ACE_WRITE_DATA, 0, skipaclchk, cr);
                if (err)
                        goto out3;

                truncate_setsize(ip, vap->va_size);

                /*
                 * XXX - Note, we are not providing any open
                 * mode flags here (like FNDELAY), so we may
                 * block if there are locks present... this
                 * should be addressed in openat().
                 */
                /* XXX - would it be OK to generate a log record here? */
                err = zfs_freesp(zp, vap->va_size, 0, 0, FALSE);
                if (err)
                        goto out3;
        }

        if (mask & (ATTR_ATIME|ATTR_MTIME) ||
            ((mask & ATTR_XVATTR) && (XVA_ISSET_REQ(xvap, XAT_HIDDEN) ||
            XVA_ISSET_REQ(xvap, XAT_READONLY) ||
            XVA_ISSET_REQ(xvap, XAT_ARCHIVE) ||
            XVA_ISSET_REQ(xvap, XAT_OFFLINE) ||
            XVA_ISSET_REQ(xvap, XAT_SPARSE) ||
            XVA_ISSET_REQ(xvap, XAT_CREATETIME) ||
            XVA_ISSET_REQ(xvap, XAT_SYSTEM)))) {
                need_policy = zfs_zaccess(zp, ACE_WRITE_ATTRIBUTES, 0,
                    skipaclchk, cr);
        }

        if (mask & (ATTR_UID|ATTR_GID)) {
                int     idmask = (mask & (ATTR_UID|ATTR_GID));
                int     take_owner;
                int     take_group;

                /*
                 * NOTE: even if a new mode is being set,
                 * we may clear S_ISUID/S_ISGID bits.
                 */

                if (!(mask & ATTR_MODE))
                        vap->va_mode = zp->z_mode;

                /*
                 * Take ownership or chgrp to group we are a member of
                 */

                take_owner = (mask & ATTR_UID) && (vap->va_uid == crgetuid(cr));
                take_group = (mask & ATTR_GID) &&
                    zfs_groupmember(zsb, vap->va_gid, cr);

                /*
                 * If both ATTR_UID and ATTR_GID are set then take_owner and
                 * take_group must both be set in order to allow taking
                 * ownership.
                 *
                 * Otherwise, send the check through secpolicy_vnode_setattr()
                 *
                 */

                if (((idmask == (ATTR_UID|ATTR_GID)) &&
                    take_owner && take_group) ||
                    ((idmask == ATTR_UID) && take_owner) ||
                    ((idmask == ATTR_GID) && take_group)) {
                        if (zfs_zaccess(zp, ACE_WRITE_OWNER, 0,
                            skipaclchk, cr) == 0) {
                                /*
                                 * Remove setuid/setgid for non-privileged users
                                 */
                                (void) secpolicy_setid_clear(vap, cr);
                                trim_mask = (mask & (ATTR_UID|ATTR_GID));
                        } else {
                                need_policy =  TRUE;
                        }
                } else {
                        need_policy =  TRUE;
                }
        }

        mutex_enter(&zp->z_lock);
        oldva.va_mode = zp->z_mode;
        zfs_fuid_map_ids(zp, cr, &oldva.va_uid, &oldva.va_gid);
        if (mask & ATTR_XVATTR) {
                /*
                 * Update xvattr mask to include only those attributes
                 * that are actually changing.
                 *
                 * the bits will be restored prior to actually setting
                 * the attributes so the caller thinks they were set.
                 */
                if (XVA_ISSET_REQ(xvap, XAT_APPENDONLY)) {
                        if (xoap->xoa_appendonly !=
                            ((zp->z_pflags & ZFS_APPENDONLY) != 0)) {
                                need_policy = TRUE;
                        } else {
                                XVA_CLR_REQ(xvap, XAT_APPENDONLY);
                                XVA_SET_REQ(tmpxvattr, XAT_APPENDONLY);
                        }
                }

                if (XVA_ISSET_REQ(xvap, XAT_NOUNLINK)) {
                        if (xoap->xoa_nounlink !=
                            ((zp->z_pflags & ZFS_NOUNLINK) != 0)) {
                                need_policy = TRUE;
                        } else {
                                XVA_CLR_REQ(xvap, XAT_NOUNLINK);
                                XVA_SET_REQ(tmpxvattr, XAT_NOUNLINK);
                        }
                }

                if (XVA_ISSET_REQ(xvap, XAT_IMMUTABLE)) {
                        if (xoap->xoa_immutable !=
                            ((zp->z_pflags & ZFS_IMMUTABLE) != 0)) {
                                need_policy = TRUE;
                        } else {
                                XVA_CLR_REQ(xvap, XAT_IMMUTABLE);
                                XVA_SET_REQ(tmpxvattr, XAT_IMMUTABLE);
                        }
                }

                if (XVA_ISSET_REQ(xvap, XAT_NODUMP)) {
                        if (xoap->xoa_nodump !=
                            ((zp->z_pflags & ZFS_NODUMP) != 0)) {
                                need_policy = TRUE;
                        } else {
                                XVA_CLR_REQ(xvap, XAT_NODUMP);
                                XVA_SET_REQ(tmpxvattr, XAT_NODUMP);
                        }
                }

                if (XVA_ISSET_REQ(xvap, XAT_AV_MODIFIED)) {
                        if (xoap->xoa_av_modified !=
                            ((zp->z_pflags & ZFS_AV_MODIFIED) != 0)) {
                                need_policy = TRUE;
                        } else {
                                XVA_CLR_REQ(xvap, XAT_AV_MODIFIED);
                                XVA_SET_REQ(tmpxvattr, XAT_AV_MODIFIED);
                        }
                }

                if (XVA_ISSET_REQ(xvap, XAT_AV_QUARANTINED)) {
                        if ((!S_ISREG(ip->i_mode) &&
                            xoap->xoa_av_quarantined) ||
                            xoap->xoa_av_quarantined !=
                            ((zp->z_pflags & ZFS_AV_QUARANTINED) != 0)) {
                                need_policy = TRUE;
                        } else {
                                XVA_CLR_REQ(xvap, XAT_AV_QUARANTINED);
                                XVA_SET_REQ(tmpxvattr, XAT_AV_QUARANTINED);
                        }
                }

                if (XVA_ISSET_REQ(xvap, XAT_REPARSE)) {
                        mutex_exit(&zp->z_lock);
                        err = EPERM;
                        goto out3;
                }

                if (need_policy == FALSE &&
                    (XVA_ISSET_REQ(xvap, XAT_AV_SCANSTAMP) ||
                    XVA_ISSET_REQ(xvap, XAT_OPAQUE))) {
                        need_policy = TRUE;
                }
        }

        mutex_exit(&zp->z_lock);

        if (mask & ATTR_MODE) {
                if (zfs_zaccess(zp, ACE_WRITE_ACL, 0, skipaclchk, cr) == 0) {
                        err = secpolicy_setid_setsticky_clear(ip, vap,
                            &oldva, cr);
                        if (err)
                                goto out3;

                        trim_mask |= ATTR_MODE;
                } else {
                        need_policy = TRUE;
                }
        }

        if (need_policy) {
                /*
                 * If trim_mask is set then take ownership
                 * has been granted or write_acl is present and user
                 * has the ability to modify mode.  In that case remove
                 * UID|GID and or MODE from mask so that
                 * secpolicy_vnode_setattr() doesn't revoke it.
                 */

                if (trim_mask) {
                        saved_mask = vap->va_mask;
                        vap->va_mask &= ~trim_mask;
                }
                err = secpolicy_vnode_setattr(cr, ip, vap, &oldva, flags,
                    (int (*)(void *, int, cred_t *))zfs_zaccess_unix, zp);
                if (err)
                        goto out3;

                if (trim_mask)
                        vap->va_mask |= saved_mask;
        }

        /*
         * secpolicy_vnode_setattr, or take ownership may have
         * changed va_mask
         */
        mask = vap->va_mask;

        if ((mask & (ATTR_UID | ATTR_GID))) {
                err = sa_lookup(zp->z_sa_hdl, SA_ZPL_XATTR(zsb),
                    &xattr_obj, sizeof (xattr_obj));

                if (err == 0 && xattr_obj) {
                        err = zfs_zget(ZTOZSB(zp), xattr_obj, &attrzp);
                        if (err)
                                goto out2;
                }
                if (mask & ATTR_UID) {
                        new_uid = zfs_fuid_create(zsb,
                            (uint64_t)vap->va_uid, cr, ZFS_OWNER, &fuidp);
                        if (new_uid != zp->z_uid &&
                            zfs_fuid_overquota(zsb, B_FALSE, new_uid)) {
                                if (attrzp)
                                        iput(ZTOI(attrzp));
                                err = EDQUOT;
                                goto out2;
                        }
                }

                if (mask & ATTR_GID) {
                        new_gid = zfs_fuid_create(zsb, (uint64_t)vap->va_gid,
                            cr, ZFS_GROUP, &fuidp);
                        if (new_gid != zp->z_gid &&
                            zfs_fuid_overquota(zsb, B_TRUE, new_gid)) {
                                if (attrzp)
                                        iput(ZTOI(attrzp));
                                err = EDQUOT;
                                goto out2;
                        }
                }
        }
        tx = dmu_tx_create(zsb->z_os);

        if (mask & ATTR_MODE) {
                uint64_t pmode = zp->z_mode;
                uint64_t acl_obj;
                new_mode = (pmode & S_IFMT) | (vap->va_mode & ~S_IFMT);

                zfs_acl_chmod_setattr(zp, &aclp, new_mode);

                mutex_enter(&zp->z_lock);
                if (!zp->z_is_sa && ((acl_obj = zfs_external_acl(zp)) != 0)) {
                        /*
                         * Are we upgrading ACL from old V0 format
                         * to V1 format?
                         */
                        if (zsb->z_version >= ZPL_VERSION_FUID &&
                            zfs_znode_acl_version(zp) ==
                            ZFS_ACL_VERSION_INITIAL) {
                                dmu_tx_hold_free(tx, acl_obj, 0,
                                    DMU_OBJECT_END);
                                dmu_tx_hold_write(tx, DMU_NEW_OBJECT,
                                    0, aclp->z_acl_bytes);
                        } else {
                                dmu_tx_hold_write(tx, acl_obj, 0,
                                    aclp->z_acl_bytes);
                        }
                } else if (!zp->z_is_sa && aclp->z_acl_bytes > ZFS_ACE_SPACE) {
                        dmu_tx_hold_write(tx, DMU_NEW_OBJECT,
                            0, aclp->z_acl_bytes);
                }
                mutex_exit(&zp->z_lock);
                dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_TRUE);
        } else {
                if ((mask & ATTR_XVATTR) &&
                    XVA_ISSET_REQ(xvap, XAT_AV_SCANSTAMP))
                        dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_TRUE);
                else
                        dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_FALSE);
        }

        if (attrzp) {
                dmu_tx_hold_sa(tx, attrzp->z_sa_hdl, B_FALSE);
        }

        fuid_dirtied = zsb->z_fuid_dirty;
        if (fuid_dirtied)
                zfs_fuid_txhold(zsb, tx);

        zfs_sa_upgrade_txholds(tx, zp);

        err = dmu_tx_assign(tx, TXG_NOWAIT);
        if (err) {
                if (err == ERESTART)
                        dmu_tx_wait(tx);
                goto out;
        }

        count = 0;
        /*
         * Set each attribute requested.
         * We group settings according to the locks they need to acquire.
         *
         * Note: you cannot set ctime directly, although it will be
         * updated as a side-effect of calling this function.
         */


        if (mask & (ATTR_UID|ATTR_GID|ATTR_MODE))
                mutex_enter(&zp->z_acl_lock);
        mutex_enter(&zp->z_lock);

        SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_FLAGS(zsb), NULL,
            &zp->z_pflags, sizeof (zp->z_pflags));

        if (attrzp) {
                if (mask & (ATTR_UID|ATTR_GID|ATTR_MODE))
                        mutex_enter(&attrzp->z_acl_lock);
                mutex_enter(&attrzp->z_lock);
                SA_ADD_BULK_ATTR(xattr_bulk, xattr_count,
                    SA_ZPL_FLAGS(zsb), NULL, &attrzp->z_pflags,
                    sizeof (attrzp->z_pflags));
        }

        if (mask & (ATTR_UID|ATTR_GID)) {

                if (mask & ATTR_UID) {
                        SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_UID(zsb), NULL,
                            &new_uid, sizeof (new_uid));
                        zp->z_uid = new_uid;
                        if (attrzp) {
                                SA_ADD_BULK_ATTR(xattr_bulk, xattr_count,
                                    SA_ZPL_UID(zsb), NULL, &new_uid,
                                    sizeof (new_uid));
                                attrzp->z_uid = new_uid;
                        }
                }

                if (mask & ATTR_GID) {
                        SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_GID(zsb),
                            NULL, &new_gid, sizeof (new_gid));
                        zp->z_gid = new_gid;
                        if (attrzp) {
                                SA_ADD_BULK_ATTR(xattr_bulk, xattr_count,
                                    SA_ZPL_GID(zsb), NULL, &new_gid,
                                    sizeof (new_gid));
                                attrzp->z_gid = new_gid;
                        }
                }
                if (!(mask & ATTR_MODE)) {
                        SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_MODE(zsb),
                            NULL, &new_mode, sizeof (new_mode));
                        new_mode = zp->z_mode;
                }
                err = zfs_acl_chown_setattr(zp);
                ASSERT(err == 0);
                if (attrzp) {
                        err = zfs_acl_chown_setattr(attrzp);
                        ASSERT(err == 0);
                }
        }

        if (mask & ATTR_MODE) {
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_MODE(zsb), NULL,
                    &new_mode, sizeof (new_mode));
                zp->z_mode = new_mode;
                ASSERT3P(aclp, !=, NULL);
                err = zfs_aclset_common(zp, aclp, cr, tx);
                ASSERT3U(err, ==, 0);
                if (zp->z_acl_cached)
                        zfs_acl_free(zp->z_acl_cached);
                zp->z_acl_cached = aclp;
                aclp = NULL;
        }


        if (mask & ATTR_ATIME) {
                ZFS_TIME_ENCODE(&vap->va_atime, zp->z_atime);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_ATIME(zsb), NULL,
                    &zp->z_atime, sizeof (zp->z_atime));
        }

        if (mask & ATTR_MTIME) {
                ZFS_TIME_ENCODE(&vap->va_mtime, mtime);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_MTIME(zsb), NULL,
                    mtime, sizeof (mtime));
        }

        /* XXX - shouldn't this be done *before* the ATIME/MTIME checks? */
        if (mask & ATTR_SIZE && !(mask & ATTR_MTIME)) {
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_MTIME(zsb),
                    NULL, mtime, sizeof (mtime));
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_CTIME(zsb), NULL,
                    &ctime, sizeof (ctime));
                zfs_tstamp_update_setup(zp, CONTENT_MODIFIED, mtime, ctime,
                    B_TRUE);
        } else if (mask != 0) {
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_CTIME(zsb), NULL,
                    &ctime, sizeof (ctime));
                zfs_tstamp_update_setup(zp, STATE_CHANGED, mtime, ctime,
                    B_TRUE);
                if (attrzp) {
                        SA_ADD_BULK_ATTR(xattr_bulk, xattr_count,
                            SA_ZPL_CTIME(zsb), NULL,
                            &ctime, sizeof (ctime));
                        zfs_tstamp_update_setup(attrzp, STATE_CHANGED,
                            mtime, ctime, B_TRUE);
                }
        }
        /*
         * Do this after setting timestamps to prevent timestamp
         * update from toggling bit
         */

        if (xoap && (mask & ATTR_XVATTR)) {

                /*
                 * restore trimmed off masks
                 * so that return masks can be set for caller.
                 */

                if (XVA_ISSET_REQ(tmpxvattr, XAT_APPENDONLY)) {
                        XVA_SET_REQ(xvap, XAT_APPENDONLY);
                }
                if (XVA_ISSET_REQ(tmpxvattr, XAT_NOUNLINK)) {
                        XVA_SET_REQ(xvap, XAT_NOUNLINK);
                }
                if (XVA_ISSET_REQ(tmpxvattr, XAT_IMMUTABLE)) {
                        XVA_SET_REQ(xvap, XAT_IMMUTABLE);
                }
                if (XVA_ISSET_REQ(tmpxvattr, XAT_NODUMP)) {
                        XVA_SET_REQ(xvap, XAT_NODUMP);
                }
                if (XVA_ISSET_REQ(tmpxvattr, XAT_AV_MODIFIED)) {
                        XVA_SET_REQ(xvap, XAT_AV_MODIFIED);
                }
                if (XVA_ISSET_REQ(tmpxvattr, XAT_AV_QUARANTINED)) {
                        XVA_SET_REQ(xvap, XAT_AV_QUARANTINED);
                }

                if (XVA_ISSET_REQ(xvap, XAT_AV_SCANSTAMP))
                        ASSERT(S_ISREG(ip->i_mode));

                zfs_xvattr_set(zp, xvap, tx);
        }

        if (fuid_dirtied)
                zfs_fuid_sync(zsb, tx);

        if (mask != 0)
                zfs_log_setattr(zilog, tx, TX_SETATTR, zp, vap, mask, fuidp);

        mutex_exit(&zp->z_lock);
        if (mask & (ATTR_UID|ATTR_GID|ATTR_MODE))
                mutex_exit(&zp->z_acl_lock);

        if (attrzp) {
                if (mask & (ATTR_UID|ATTR_GID|ATTR_MODE))
                        mutex_exit(&attrzp->z_acl_lock);
                mutex_exit(&attrzp->z_lock);
        }
out:
        if (err == 0 && attrzp) {
                err2 = sa_bulk_update(attrzp->z_sa_hdl, xattr_bulk,
                    xattr_count, tx);
                ASSERT(err2 == 0);
        }

        if (attrzp)
                iput(ZTOI(attrzp));
        if (aclp)
                zfs_acl_free(aclp);

        if (fuidp) {
                zfs_fuid_info_free(fuidp);
                fuidp = NULL;
        }

        if (err) {
                dmu_tx_abort(tx);
                if (err == ERESTART)
                        goto top;
        } else {
                err2 = sa_bulk_update(zp->z_sa_hdl, bulk, count, tx);
                dmu_tx_commit(tx);
                zfs_inode_update(zp);
        }

out2:
        if (zsb->z_os->os_sync == ZFS_SYNC_ALWAYS)
                zil_commit(zilog, 0);

out3:
        kmem_free(xattr_bulk, sizeof(sa_bulk_attr_t) * 7);
        kmem_free(bulk, sizeof(sa_bulk_attr_t) * 7);
        kmem_free(tmpxvattr, sizeof(xvattr_t));
        ZFS_EXIT(zsb);
        return (err);
}
EXPORT_SYMBOL(zfs_setattr);

typedef struct zfs_zlock {
        krwlock_t       *zl_rwlock;     /* lock we acquired */
        znode_t         *zl_znode;      /* znode we held */
        struct zfs_zlock *zl_next;      /* next in list */
} zfs_zlock_t;

/*
 * Drop locks and release vnodes that were held by zfs_rename_lock().
 */
static void
zfs_rename_unlock(zfs_zlock_t **zlpp)
{
        zfs_zlock_t *zl;

        while ((zl = *zlpp) != NULL) {
                if (zl->zl_znode != NULL)
                        iput(ZTOI(zl->zl_znode));
                rw_exit(zl->zl_rwlock);
                *zlpp = zl->zl_next;
                kmem_free(zl, sizeof (*zl));
        }
}

/*
 * Search back through the directory tree, using the ".." entries.
 * Lock each directory in the chain to prevent concurrent renames.
 * Fail any attempt to move a directory into one of its own descendants.
 * XXX - z_parent_lock can overlap with map or grow locks
 */
static int
zfs_rename_lock(znode_t *szp, znode_t *tdzp, znode_t *sdzp, zfs_zlock_t **zlpp)
{
        zfs_zlock_t     *zl;
        znode_t         *zp = tdzp;
        uint64_t        rootid = ZTOZSB(zp)->z_root;
        uint64_t        oidp = zp->z_id;
        krwlock_t       *rwlp = &szp->z_parent_lock;
        krw_t           rw = RW_WRITER;

        /*
         * First pass write-locks szp and compares to zp->z_id.
         * Later passes read-lock zp and compare to zp->z_parent.
         */
        do {
                if (!rw_tryenter(rwlp, rw)) {
                        /*
                         * Another thread is renaming in this path.
                         * Note that if we are a WRITER, we don't have any
                         * parent_locks held yet.
                         */
                        if (rw == RW_READER && zp->z_id > szp->z_id) {
                                /*
                                 * Drop our locks and restart
                                 */
                                zfs_rename_unlock(&zl);
                                *zlpp = NULL;
                                zp = tdzp;
                                oidp = zp->z_id;
                                rwlp = &szp->z_parent_lock;
                                rw = RW_WRITER;
                                continue;
                        } else {
                                /*
                                 * Wait for other thread to drop its locks
                                 */
                                rw_enter(rwlp, rw);
                        }
                }

                zl = kmem_alloc(sizeof (*zl), KM_SLEEP);
                zl->zl_rwlock = rwlp;
                zl->zl_znode = NULL;
                zl->zl_next = *zlpp;
                *zlpp = zl;

                if (oidp == szp->z_id)          /* We're a descendant of szp */
                        return (EINVAL);

                if (oidp == rootid)             /* We've hit the top */
                        return (0);

                if (rw == RW_READER) {          /* i.e. not the first pass */
                        int error = zfs_zget(ZTOZSB(zp), oidp, &zp);
                        if (error)
                                return (error);
                        zl->zl_znode = zp;
                }
                (void) sa_lookup(zp->z_sa_hdl, SA_ZPL_PARENT(ZTOZSB(zp)),
                    &oidp, sizeof (oidp));
                rwlp = &zp->z_parent_lock;
                rw = RW_READER;

        } while (zp->z_id != sdzp->z_id);

        return (0);
}

/*
 * Move an entry from the provided source directory to the target
 * directory.  Change the entry name as indicated.
 *
 *      IN:     sdip    - Source directory containing the "old entry".
 *              snm     - Old entry name.
 *              tdip    - Target directory to contain the "new entry".
 *              tnm     - New entry name.
 *              cr      - credentials of caller.
 *              flags   - case flags
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      sdip,tdip - ctime|mtime updated
 */
/*ARGSUSED*/
int
zfs_rename(struct inode *sdip, char *snm, struct inode *tdip, char *tnm,
    cred_t *cr, int flags)
{
        znode_t         *tdzp, *szp, *tzp;
        znode_t         *sdzp = ITOZ(sdip);
        zfs_sb_t        *zsb = ITOZSB(sdip);
        zilog_t         *zilog;
        zfs_dirlock_t   *sdl, *tdl;
        dmu_tx_t        *tx;
        zfs_zlock_t     *zl;
        int             cmp, serr, terr;
        int             error = 0;
        int             zflg = 0;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(sdzp);
        zilog = zsb->z_log;

        if (tdip->i_sb != sdip->i_sb) {
                ZFS_EXIT(zsb);
                return (EXDEV);
        }

        tdzp = ITOZ(tdip);
        ZFS_VERIFY_ZP(tdzp);
        if (zsb->z_utf8 && u8_validate(tnm,
            strlen(tnm), NULL, U8_VALIDATE_ENTIRE, &error) < 0) {
                ZFS_EXIT(zsb);
                return (EILSEQ);
        }

        if (flags & FIGNORECASE)
                zflg |= ZCILOOK;

top:
        szp = NULL;
        tzp = NULL;
        zl = NULL;

        /*
         * This is to prevent the creation of links into attribute space
         * by renaming a linked file into/outof an attribute directory.
         * See the comment in zfs_link() for why this is considered bad.
         */
        if ((tdzp->z_pflags & ZFS_XATTR) != (sdzp->z_pflags & ZFS_XATTR)) {
                ZFS_EXIT(zsb);
                return (EINVAL);
        }

        /*
         * Lock source and target directory entries.  To prevent deadlock,
         * a lock ordering must be defined.  We lock the directory with
         * the smallest object id first, or if it's a tie, the one with
         * the lexically first name.
         */
        if (sdzp->z_id < tdzp->z_id) {
                cmp = -1;
        } else if (sdzp->z_id > tdzp->z_id) {
                cmp = 1;
        } else {
                /*
                 * First compare the two name arguments without
                 * considering any case folding.
                 */
                int nofold = (zsb->z_norm & ~U8_TEXTPREP_TOUPPER);

                cmp = u8_strcmp(snm, tnm, 0, nofold, U8_UNICODE_LATEST, &error);
                ASSERT(error == 0 || !zsb->z_utf8);
                if (cmp == 0) {
                        /*
                         * POSIX: "If the old argument and the new argument
                         * both refer to links to the same existing file,
                         * the rename() function shall return successfully
                         * and perform no other action."
                         */
                        ZFS_EXIT(zsb);
                        return (0);
                }
                /*
                 * If the file system is case-folding, then we may
                 * have some more checking to do.  A case-folding file
                 * system is either supporting mixed case sensitivity
                 * access or is completely case-insensitive.  Note
                 * that the file system is always case preserving.
                 *
                 * In mixed sensitivity mode case sensitive behavior
                 * is the default.  FIGNORECASE must be used to
                 * explicitly request case insensitive behavior.
                 *
                 * If the source and target names provided differ only
                 * by case (e.g., a request to rename 'tim' to 'Tim'),
                 * we will treat this as a special case in the
                 * case-insensitive mode: as long as the source name
                 * is an exact match, we will allow this to proceed as
                 * a name-change request.
                 */
                if ((zsb->z_case == ZFS_CASE_INSENSITIVE ||
                    (zsb->z_case == ZFS_CASE_MIXED &&
                    flags & FIGNORECASE)) &&
                    u8_strcmp(snm, tnm, 0, zsb->z_norm, U8_UNICODE_LATEST,
                    &error) == 0) {
                        /*
                         * case preserving rename request, require exact
                         * name matches
                         */
                        zflg |= ZCIEXACT;
                        zflg &= ~ZCILOOK;
                }
        }

        /*
         * If the source and destination directories are the same, we should
         * grab the z_name_lock of that directory only once.
         */
        if (sdzp == tdzp) {
                zflg |= ZHAVELOCK;
                rw_enter(&sdzp->z_name_lock, RW_READER);
        }

        if (cmp < 0) {
                serr = zfs_dirent_lock(&sdl, sdzp, snm, &szp,
                    ZEXISTS | zflg, NULL, NULL);
                terr = zfs_dirent_lock(&tdl,
                    tdzp, tnm, &tzp, ZRENAMING | zflg, NULL, NULL);
        } else {
                terr = zfs_dirent_lock(&tdl,
                    tdzp, tnm, &tzp, zflg, NULL, NULL);
                serr = zfs_dirent_lock(&sdl,
                    sdzp, snm, &szp, ZEXISTS | ZRENAMING | zflg,
                    NULL, NULL);
        }

        if (serr) {
                /*
                 * Source entry invalid or not there.
                 */
                if (!terr) {
                        zfs_dirent_unlock(tdl);
                        if (tzp)
                                iput(ZTOI(tzp));
                }

                if (sdzp == tdzp)
                        rw_exit(&sdzp->z_name_lock);

                if (strcmp(snm, "..") == 0)
                        serr = EINVAL;
                ZFS_EXIT(zsb);
                return (serr);
        }
        if (terr) {
                zfs_dirent_unlock(sdl);
                iput(ZTOI(szp));

                if (sdzp == tdzp)
                        rw_exit(&sdzp->z_name_lock);

                if (strcmp(tnm, "..") == 0)
                        terr = EINVAL;
                ZFS_EXIT(zsb);
                return (terr);
        }

        /*
         * Must have write access at the source to remove the old entry
         * and write access at the target to create the new entry.
         * Note that if target and source are the same, this can be
         * done in a single check.
         */

        if ((error = zfs_zaccess_rename(sdzp, szp, tdzp, tzp, cr)))
                goto out;

        if (S_ISDIR(ZTOI(szp)->i_mode)) {
                /*
                 * Check to make sure rename is valid.
                 * Can't do a move like this: /usr/a/b to /usr/a/b/c/d
                 */
                if ((error = zfs_rename_lock(szp, tdzp, sdzp, &zl)))
                        goto out;
        }

        /*
         * Does target exist?
         */
        if (tzp) {
                /*
                 * Source and target must be the same type.
                 */
                if (S_ISDIR(ZTOI(szp)->i_mode)) {
                        if (!S_ISDIR(ZTOI(tzp)->i_mode)) {
                                error = ENOTDIR;
                                goto out;
                        }
                } else {
                        if (S_ISDIR(ZTOI(tzp)->i_mode)) {
                                error = EISDIR;
                                goto out;
                        }
                }
                /*
                 * POSIX dictates that when the source and target
                 * entries refer to the same file object, rename
                 * must do nothing and exit without error.
                 */
                if (szp->z_id == tzp->z_id) {
                        error = 0;
                        goto out;
                }
        }

        tx = dmu_tx_create(zsb->z_os);
        dmu_tx_hold_sa(tx, szp->z_sa_hdl, B_FALSE);
        dmu_tx_hold_sa(tx, sdzp->z_sa_hdl, B_FALSE);
        dmu_tx_hold_zap(tx, sdzp->z_id, FALSE, snm);
        dmu_tx_hold_zap(tx, tdzp->z_id, TRUE, tnm);
        if (sdzp != tdzp) {
                dmu_tx_hold_sa(tx, tdzp->z_sa_hdl, B_FALSE);
                zfs_sa_upgrade_txholds(tx, tdzp);
        }
        if (tzp) {
                dmu_tx_hold_sa(tx, tzp->z_sa_hdl, B_FALSE);
                zfs_sa_upgrade_txholds(tx, tzp);
        }

        zfs_sa_upgrade_txholds(tx, szp);
        dmu_tx_hold_zap(tx, zsb->z_unlinkedobj, FALSE, NULL);
        error = dmu_tx_assign(tx, TXG_NOWAIT);
        if (error) {
                if (zl != NULL)
                        zfs_rename_unlock(&zl);
                zfs_dirent_unlock(sdl);
                zfs_dirent_unlock(tdl);

                if (sdzp == tdzp)
                        rw_exit(&sdzp->z_name_lock);

                iput(ZTOI(szp));
                if (tzp)
                        iput(ZTOI(tzp));
                if (error == ERESTART) {
                        dmu_tx_wait(tx);
                        dmu_tx_abort(tx);
                        goto top;
                }
                dmu_tx_abort(tx);
                ZFS_EXIT(zsb);
                return (error);
        }

        if (tzp)        /* Attempt to remove the existing target */
                error = zfs_link_destroy(tdl, tzp, tx, zflg, NULL);

        if (error == 0) {
                error = zfs_link_create(tdl, szp, tx, ZRENAMING);
                if (error == 0) {
                        szp->z_pflags |= ZFS_AV_MODIFIED;

                        error = sa_update(szp->z_sa_hdl, SA_ZPL_FLAGS(zsb),
                            (void *)&szp->z_pflags, sizeof (uint64_t), tx);
                        ASSERT3U(error, ==, 0);

                        error = zfs_link_destroy(sdl, szp, tx, ZRENAMING, NULL);
                        if (error == 0) {
                                zfs_log_rename(zilog, tx, TX_RENAME |
                                    (flags & FIGNORECASE ? TX_CI : 0), sdzp,
                                    sdl->dl_name, tdzp, tdl->dl_name, szp);
                        } else {
                                /*
                                 * At this point, we have successfully created
                                 * the target name, but have failed to remove
                                 * the source name.  Since the create was done
                                 * with the ZRENAMING flag, there are
                                 * complications; for one, the link count is
                                 * wrong.  The easiest way to deal with this
                                 * is to remove the newly created target, and
                                 * return the original error.  This must
                                 * succeed; fortunately, it is very unlikely to
                                 * fail, since we just created it.
                                 */
                                VERIFY3U(zfs_link_destroy(tdl, szp, tx,
                                    ZRENAMING, NULL), ==, 0);
                        }
                }
        }

        dmu_tx_commit(tx);
out:
        if (zl != NULL)
                zfs_rename_unlock(&zl);

        zfs_dirent_unlock(sdl);
        zfs_dirent_unlock(tdl);

        zfs_inode_update(sdzp);
        if (sdzp == tdzp)
                rw_exit(&sdzp->z_name_lock);

        if (sdzp != tdzp)
                zfs_inode_update(tdzp);

        zfs_inode_update(szp);
        iput(ZTOI(szp));
        if (tzp) {
                zfs_inode_update(tzp);
                iput(ZTOI(tzp));
        }

        if (zsb->z_os->os_sync == ZFS_SYNC_ALWAYS)
                zil_commit(zilog, 0);

        ZFS_EXIT(zsb);
        return (error);
}
EXPORT_SYMBOL(zfs_rename);

/*
 * Insert the indicated symbolic reference entry into the directory.
 *
 *      IN:     dip     - Directory to contain new symbolic link.
 *              link    - Name for new symlink entry.
 *              vap     - Attributes of new entry.
 *              target  - Target path of new symlink.
 *
 *              cr      - credentials of caller.
 *              flags   - case flags
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      dip - ctime|mtime updated
 */
/*ARGSUSED*/
int
zfs_symlink(struct inode *dip, char *name, vattr_t *vap, char *link,
    struct inode **ipp, cred_t *cr, int flags)
{
        znode_t         *zp, *dzp = ITOZ(dip);
        zfs_dirlock_t   *dl;
        dmu_tx_t        *tx;
        zfs_sb_t        *zsb = ITOZSB(dip);
        zilog_t         *zilog;
        uint64_t        len = strlen(link);
        int             error;
        int             zflg = ZNEW;
        zfs_acl_ids_t   acl_ids;
        boolean_t       fuid_dirtied;
        uint64_t        txtype = TX_SYMLINK;

        ASSERT(S_ISLNK(vap->va_mode));

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(dzp);
        zilog = zsb->z_log;

        if (zsb->z_utf8 && u8_validate(name, strlen(name),
            NULL, U8_VALIDATE_ENTIRE, &error) < 0) {
                ZFS_EXIT(zsb);
                return (EILSEQ);
        }
        if (flags & FIGNORECASE)
                zflg |= ZCILOOK;

        if (len > MAXPATHLEN) {
                ZFS_EXIT(zsb);
                return (ENAMETOOLONG);
        }

        if ((error = zfs_acl_ids_create(dzp, 0,
            vap, cr, NULL, &acl_ids)) != 0) {
                ZFS_EXIT(zsb);
                return (error);
        }
top:
        *ipp = NULL;

        /*
         * Attempt to lock directory; fail if entry already exists.
         */
        error = zfs_dirent_lock(&dl, dzp, name, &zp, zflg, NULL, NULL);
        if (error) {
                zfs_acl_ids_free(&acl_ids);
                ZFS_EXIT(zsb);
                return (error);
        }

        if ((error = zfs_zaccess(dzp, ACE_ADD_FILE, 0, B_FALSE, cr))) {
                zfs_acl_ids_free(&acl_ids);
                zfs_dirent_unlock(dl);
                ZFS_EXIT(zsb);
                return (error);
        }

        if (zfs_acl_ids_overquota(zsb, &acl_ids)) {
                zfs_acl_ids_free(&acl_ids);
                zfs_dirent_unlock(dl);
                ZFS_EXIT(zsb);
                return (EDQUOT);
        }
        tx = dmu_tx_create(zsb->z_os);
        fuid_dirtied = zsb->z_fuid_dirty;
        dmu_tx_hold_write(tx, DMU_NEW_OBJECT, 0, MAX(1, len));
        dmu_tx_hold_zap(tx, dzp->z_id, TRUE, name);
        dmu_tx_hold_sa_create(tx, acl_ids.z_aclp->z_acl_bytes +
            ZFS_SA_BASE_ATTR_SIZE + len);
        dmu_tx_hold_sa(tx, dzp->z_sa_hdl, B_FALSE);
        if (!zsb->z_use_sa && acl_ids.z_aclp->z_acl_bytes > ZFS_ACE_SPACE) {
                dmu_tx_hold_write(tx, DMU_NEW_OBJECT, 0,
                    acl_ids.z_aclp->z_acl_bytes);
        }
        if (fuid_dirtied)
                zfs_fuid_txhold(zsb, tx);
        error = dmu_tx_assign(tx, TXG_NOWAIT);
        if (error) {
                zfs_dirent_unlock(dl);
                if (error == ERESTART) {
                        dmu_tx_wait(tx);
                        dmu_tx_abort(tx);
                        goto top;
                }
                zfs_acl_ids_free(&acl_ids);
                dmu_tx_abort(tx);
                ZFS_EXIT(zsb);
                return (error);
        }

        /*
         * Create a new object for the symlink.
         * for version 4 ZPL datsets the symlink will be an SA attribute
         */
        zfs_mknode(dzp, vap, tx, cr, 0, &zp, &acl_ids);

        if (fuid_dirtied)
                zfs_fuid_sync(zsb, tx);

        mutex_enter(&zp->z_lock);
        if (zp->z_is_sa)
                error = sa_update(zp->z_sa_hdl, SA_ZPL_SYMLINK(zsb),
                    link, len, tx);
        else
                zfs_sa_symlink(zp, link, len, tx);
        mutex_exit(&zp->z_lock);

        zp->z_size = len;
        (void) sa_update(zp->z_sa_hdl, SA_ZPL_SIZE(zsb),
            &zp->z_size, sizeof (zp->z_size), tx);
        /*
         * Insert the new object into the directory.
         */
        (void) zfs_link_create(dl, zp, tx, ZNEW);

        if (flags & FIGNORECASE)
                txtype |= TX_CI;
        zfs_log_symlink(zilog, tx, txtype, dzp, zp, name, link);

        zfs_inode_update(dzp);
        zfs_inode_update(zp);

        zfs_acl_ids_free(&acl_ids);

        dmu_tx_commit(tx);

        zfs_dirent_unlock(dl);

        *ipp = ZTOI(zp);

        if (zsb->z_os->os_sync == ZFS_SYNC_ALWAYS)
                zil_commit(zilog, 0);

        ZFS_EXIT(zsb);
        return (error);
}
EXPORT_SYMBOL(zfs_symlink);

/*
 * Return, in the buffer contained in the provided uio structure,
 * the symbolic path referred to by ip.
 *
 *      IN:     ip      - inode of symbolic link
 *              uio     - structure to contain the link path.
 *              cr      - credentials of caller.
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      ip - atime updated
 */
/* ARGSUSED */
int
zfs_readlink(struct inode *ip, uio_t *uio, cred_t *cr)
{
        znode_t         *zp = ITOZ(ip);
        zfs_sb_t        *zsb = ITOZSB(ip);
        int             error;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        mutex_enter(&zp->z_lock);
        if (zp->z_is_sa)
                error = sa_lookup_uio(zp->z_sa_hdl,
                    SA_ZPL_SYMLINK(zsb), uio);
        else
                error = zfs_sa_readlink(zp, uio);
        mutex_exit(&zp->z_lock);

        ZFS_ACCESSTIME_STAMP(zsb, zp);
        zfs_inode_update(zp);
        ZFS_EXIT(zsb);
        return (error);
}
EXPORT_SYMBOL(zfs_readlink);

/*
 * Insert a new entry into directory tdip referencing sip.
 *
 *      IN:     tdip    - Directory to contain new entry.
 *              sip     - inode of new entry.
 *              name    - name of new entry.
 *              cr      - credentials of caller.
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      tdip - ctime|mtime updated
 *       sip - ctime updated
 */
/* ARGSUSED */
int
zfs_link(struct inode *tdip, struct inode *sip, char *name, cred_t *cr)
{
        znode_t         *dzp = ITOZ(tdip);
        znode_t         *tzp, *szp;
        zfs_sb_t        *zsb = ITOZSB(tdip);
        zilog_t         *zilog;
        zfs_dirlock_t   *dl;
        dmu_tx_t        *tx;
        int             error;
        int             zf = ZNEW;
        uint64_t        parent;
        uid_t           owner;

        ASSERT(S_ISDIR(tdip->i_mode));

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(dzp);
        zilog = zsb->z_log;

        /*
         * POSIX dictates that we return EPERM here.
         * Better choices include ENOTSUP or EISDIR.
         */
        if (S_ISDIR(sip->i_mode)) {
                ZFS_EXIT(zsb);
                return (EPERM);
        }

        if (sip->i_sb != tdip->i_sb) {
                ZFS_EXIT(zsb);
                return (EXDEV);
        }

        szp = ITOZ(sip);
        ZFS_VERIFY_ZP(szp);

        /* Prevent links to .zfs/shares files */

        if ((error = sa_lookup(szp->z_sa_hdl, SA_ZPL_PARENT(zsb),
            &parent, sizeof (uint64_t))) != 0) {
                ZFS_EXIT(zsb);
                return (error);
        }
        if (parent == zsb->z_shares_dir) {
                ZFS_EXIT(zsb);
                return (EPERM);
        }

        if (zsb->z_utf8 && u8_validate(name,
            strlen(name), NULL, U8_VALIDATE_ENTIRE, &error) < 0) {
                ZFS_EXIT(zsb);
                return (EILSEQ);
        }
#ifdef HAVE_PN_UTILS
        if (flags & FIGNORECASE)
                zf |= ZCILOOK;
#endif /* HAVE_PN_UTILS */

        /*
         * We do not support links between attributes and non-attributes
         * because of the potential security risk of creating links
         * into "normal" file space in order to circumvent restrictions
         * imposed in attribute space.
         */
        if ((szp->z_pflags & ZFS_XATTR) != (dzp->z_pflags & ZFS_XATTR)) {
                ZFS_EXIT(zsb);
                return (EINVAL);
        }

        owner = zfs_fuid_map_id(zsb, szp->z_uid, cr, ZFS_OWNER);
        if (owner != crgetuid(cr) && secpolicy_basic_link(cr) != 0) {
                ZFS_EXIT(zsb);
                return (EPERM);
        }

        if ((error = zfs_zaccess(dzp, ACE_ADD_FILE, 0, B_FALSE, cr))) {
                ZFS_EXIT(zsb);
                return (error);
        }

top:
        /*
         * Attempt to lock directory; fail if entry already exists.
         */
        error = zfs_dirent_lock(&dl, dzp, name, &tzp, zf, NULL, NULL);
        if (error) {
                ZFS_EXIT(zsb);
                return (error);
        }

        tx = dmu_tx_create(zsb->z_os);
        dmu_tx_hold_sa(tx, szp->z_sa_hdl, B_FALSE);
        dmu_tx_hold_zap(tx, dzp->z_id, TRUE, name);
        zfs_sa_upgrade_txholds(tx, szp);
        zfs_sa_upgrade_txholds(tx, dzp);
        error = dmu_tx_assign(tx, TXG_NOWAIT);
        if (error) {
                zfs_dirent_unlock(dl);
                if (error == ERESTART) {
                        dmu_tx_wait(tx);
                        dmu_tx_abort(tx);
                        goto top;
                }
                dmu_tx_abort(tx);
                ZFS_EXIT(zsb);
                return (error);
        }

        error = zfs_link_create(dl, szp, tx, 0);

        if (error == 0) {
                uint64_t txtype = TX_LINK;
#ifdef HAVE_PN_UTILS
                if (flags & FIGNORECASE)
                        txtype |= TX_CI;
#endif /* HAVE_PN_UTILS */
                zfs_log_link(zilog, tx, txtype, dzp, szp, name);
        }

        dmu_tx_commit(tx);

        zfs_dirent_unlock(dl);

        if (zsb->z_os->os_sync == ZFS_SYNC_ALWAYS)
                zil_commit(zilog, 0);

        zfs_inode_update(dzp);
        zfs_inode_update(szp);
        ZFS_EXIT(zsb);
        return (error);
}
EXPORT_SYMBOL(zfs_link);

static void
zfs_putpage_commit_cb(void *arg, int error)
{
        struct page *pp = arg;

        if (error) {
                __set_page_dirty_nobuffers(pp);

                if (error != ECANCELED)
                        SetPageError(pp);
        } else {
                ClearPageError(pp);
        }

        end_page_writeback(pp);
}

/*
 * Push a page out to disk, once the page is on stable storage the
 * registered commit callback will be run as notification of completion.
 *
 *      IN:     ip      - page mapped for inode.
 *              pp      - page to push (page is locked)
 *              wbc     - writeback control data
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      ip - ctime|mtime updated
 */
/* ARGSUSED */
int
zfs_putpage(struct inode *ip, struct page *pp, struct writeback_control *wbc)
{
        znode_t         *zp = ITOZ(ip);
        zfs_sb_t        *zsb = ITOZSB(ip);
        loff_t          offset;
        loff_t          pgoff;
        unsigned int    pglen;
        rl_t            *rl;
        dmu_tx_t        *tx;
        caddr_t         va;
        int             err = 0;
        uint64_t        mtime[2], ctime[2];
        sa_bulk_attr_t  bulk[3];
        int             cnt = 0;
        int             sync;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        ASSERT(PageLocked(pp));

        pgoff = page_offset(pp);     /* Page byte-offset in file */
        offset = i_size_read(ip);    /* File length in bytes */
        pglen = MIN(PAGE_CACHE_SIZE, /* Page length in bytes */
            P2ROUNDUP(offset, PAGE_CACHE_SIZE)-pgoff);

        /* Page is beyond end of file */
        if (pgoff >= offset) {
                unlock_page(pp);
                ZFS_EXIT(zsb);
                return (0);
        }

        /* Truncate page length to end of file */
        if (pgoff + pglen > offset)
                pglen = offset - pgoff;

#if 0
        /*
         * FIXME: Allow mmap writes past its quota.  The correct fix
         * is to register a page_mkwrite() handler to count the page
         * against its quota when it is about to be dirtied.
         */
        if (zfs_owner_overquota(zsb, zp, B_FALSE) ||
            zfs_owner_overquota(zsb, zp, B_TRUE)) {
                err = EDQUOT;
        }
#endif

        set_page_writeback(pp);
        unlock_page(pp);

        rl = zfs_range_lock(zp, pgoff, pglen, RL_WRITER);
        tx = dmu_tx_create(zsb->z_os);

        sync = ((zsb->z_os->os_sync == ZFS_SYNC_ALWAYS) ||
                (wbc->sync_mode == WB_SYNC_ALL));
        if (!sync)
                dmu_tx_callback_register(tx, zfs_putpage_commit_cb, pp);

        dmu_tx_hold_write(tx, zp->z_id, pgoff, pglen);

        dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_FALSE);
        zfs_sa_upgrade_txholds(tx, zp);
        err = dmu_tx_assign(tx, TXG_NOWAIT);
        if (err != 0) {
                if (err == ERESTART)
                        dmu_tx_wait(tx);

                /* Will call all registered commit callbacks */
                dmu_tx_abort(tx);

                /*
                 * For the synchronous case the commit callback must be
                 * explicitly called because there is no registered callback.
                 */
                if (sync)
                        zfs_putpage_commit_cb(pp, ECANCELED);

                zfs_range_unlock(rl);
                ZFS_EXIT(zsb);
                return (err);
        }

        va = kmap(pp);
        ASSERT3U(pglen, <=, PAGE_CACHE_SIZE);
        dmu_write(zsb->z_os, zp->z_id, pgoff, pglen, va, tx);
        kunmap(pp);

        SA_ADD_BULK_ATTR(bulk, cnt, SA_ZPL_MTIME(zsb), NULL, &mtime, 16);
        SA_ADD_BULK_ATTR(bulk, cnt, SA_ZPL_CTIME(zsb), NULL, &ctime, 16);
        SA_ADD_BULK_ATTR(bulk, cnt, SA_ZPL_FLAGS(zsb), NULL, &zp->z_pflags, 8);

        /* Preserve the mtime and ctime provided by the inode */
        ZFS_TIME_ENCODE(&ip->i_mtime, mtime);
        ZFS_TIME_ENCODE(&ip->i_ctime, ctime);
        zp->z_atime_dirty = 0;
        zp->z_seq++;

        err = sa_bulk_update(zp->z_sa_hdl, bulk, cnt, tx);

        zfs_log_write(zsb->z_log, tx, TX_WRITE, zp, pgoff, pglen, 0);
        dmu_tx_commit(tx);

        zfs_range_unlock(rl);

        if (sync) {
                zil_commit(zsb->z_log, zp->z_id);
                zfs_putpage_commit_cb(pp, err);
        }

        ZFS_EXIT(zsb);
        return (err);
}

/*
 * Update the system attributes when the inode has been dirtied.  For the
 * moment we're conservative and only update the atime, mtime, and ctime.
 */
int
zfs_dirty_inode(struct inode *ip, int flags)
{
        znode_t         *zp = ITOZ(ip);
        zfs_sb_t        *zsb = ITOZSB(ip);
        dmu_tx_t        *tx;
        uint64_t        atime[2], mtime[2], ctime[2];
        sa_bulk_attr_t  bulk[3];
        int             error;
        int             cnt = 0;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        tx = dmu_tx_create(zsb->z_os);

        dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_FALSE);
        zfs_sa_upgrade_txholds(tx, zp);

        error = dmu_tx_assign(tx, TXG_WAIT);
        if (error) {
                dmu_tx_abort(tx);
                goto out;
        }

        mutex_enter(&zp->z_lock);
        SA_ADD_BULK_ATTR(bulk, cnt, SA_ZPL_ATIME(zsb), NULL, &atime, 16);
        SA_ADD_BULK_ATTR(bulk, cnt, SA_ZPL_MTIME(zsb), NULL, &mtime, 16);
        SA_ADD_BULK_ATTR(bulk, cnt, SA_ZPL_CTIME(zsb), NULL, &ctime, 16);

        /* Preserve the mtime and ctime provided by the inode */
        ZFS_TIME_ENCODE(&ip->i_atime, atime);
        ZFS_TIME_ENCODE(&ip->i_mtime, mtime);
        ZFS_TIME_ENCODE(&ip->i_ctime, ctime);
        zp->z_atime_dirty = 0;

        error = sa_bulk_update(zp->z_sa_hdl, bulk, cnt, tx);
        mutex_exit(&zp->z_lock);

        dmu_tx_commit(tx);
out:
        ZFS_EXIT(zsb);
        return (error);
}
EXPORT_SYMBOL(zfs_dirty_inode);

/*ARGSUSED*/
void
zfs_inactive(struct inode *ip)
{
        znode_t *zp = ITOZ(ip);
        zfs_sb_t *zsb = ITOZSB(ip);
        int error;

        if (zfsctl_is_node(ip)) {
                zfsctl_inode_inactive(ip);
                return;
        }

        rw_enter(&zsb->z_teardown_inactive_lock, RW_READER);
        if (zp->z_sa_hdl == NULL) {
                rw_exit(&zsb->z_teardown_inactive_lock);
                return;
        }

        if (zp->z_atime_dirty && zp->z_unlinked == 0) {
                dmu_tx_t *tx = dmu_tx_create(zsb->z_os);

                dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_FALSE);
                zfs_sa_upgrade_txholds(tx, zp);
                error = dmu_tx_assign(tx, TXG_WAIT);
                if (error) {
                        dmu_tx_abort(tx);
                } else {
                        mutex_enter(&zp->z_lock);
                        (void) sa_update(zp->z_sa_hdl, SA_ZPL_ATIME(zsb),
                            (void *)&zp->z_atime, sizeof (zp->z_atime), tx);
                        zp->z_atime_dirty = 0;
                        mutex_exit(&zp->z_lock);
                        dmu_tx_commit(tx);
                }
        }

        zfs_zinactive(zp);
        rw_exit(&zsb->z_teardown_inactive_lock);
}
EXPORT_SYMBOL(zfs_inactive);

/*
 * Bounds-check the seek operation.
 *
 *      IN:     ip      - inode seeking within
 *              ooff    - old file offset
 *              noffp   - pointer to new file offset
 *              ct      - caller context
 *
 *      RETURN: 0 if success
 *              EINVAL if new offset invalid
 */
/* ARGSUSED */
int
zfs_seek(struct inode *ip, offset_t ooff, offset_t *noffp)
{
        if (S_ISDIR(ip->i_mode))
                return (0);
        return ((*noffp < 0 || *noffp > MAXOFFSET_T) ? EINVAL : 0);
}
EXPORT_SYMBOL(zfs_seek);

/*
 * Fill pages with data from the disk.
 */
static int
zfs_fillpage(struct inode *ip, struct page *pl[], int nr_pages)
{
        znode_t     *zp = ITOZ(ip);
        zfs_sb_t    *zsb = ITOZSB(ip);
        objset_t    *os;
        struct page *cur_pp;
        u_offset_t  io_off, total;
        size_t      io_len;
        loff_t      i_size;
        unsigned    page_idx;
        int         err;

        os     = zsb->z_os;
        io_len = nr_pages << PAGE_CACHE_SHIFT;
        i_size = i_size_read(ip);
        io_off = page_offset(pl[0]);

        if (io_off + io_len > i_size)
                io_len = i_size - io_off;

        /*
         * Iterate over list of pages and read each page individually.
         */
        page_idx = 0;
        cur_pp   = pl[0];
        for (total = io_off + io_len; io_off < total; io_off += PAGESIZE) {
                caddr_t va;

                va = kmap(cur_pp);
                err = dmu_read(os, zp->z_id, io_off, PAGESIZE, va,
                    DMU_READ_PREFETCH);
                kunmap(cur_pp);
                if (err) {
                        /* convert checksum errors into IO errors */
                        if (err == ECKSUM)
                                err = EIO;
                        return (err);
                }
                cur_pp = pl[++page_idx];
        }

        return (0);
}

/*
 * Uses zfs_fillpage to read data from the file and fill the pages.
 *
 *      IN:     ip       - inode of file to get data from.
 *              pl       - list of pages to read
 *              nr_pages - number of pages to read
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      vp - atime updated
 */
/* ARGSUSED */
int
zfs_getpage(struct inode *ip, struct page *pl[], int nr_pages)
{
        znode_t  *zp  = ITOZ(ip);
        zfs_sb_t *zsb = ITOZSB(ip);
        int      err;

        if (pl == NULL)
                return (0);

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        err = zfs_fillpage(ip, pl, nr_pages);

        if (!err)
                ZFS_ACCESSTIME_STAMP(zsb, zp);

        ZFS_EXIT(zsb);
        return (err);
}
EXPORT_SYMBOL(zfs_getpage);

/*
 * Check ZFS specific permissions to memory map a section of a file.
 *
 *      IN:     ip      - inode of the file to mmap
 *              off     - file offset
 *              addrp   - start address in memory region
 *              len     - length of memory region
 *              vm_flags- address flags
 *
 *      RETURN: 0 if success
 *              error code if failure
 */
/*ARGSUSED*/
int
zfs_map(struct inode *ip, offset_t off, caddr_t *addrp, size_t len,
    unsigned long vm_flags)
{
        znode_t  *zp = ITOZ(ip);
        zfs_sb_t *zsb = ITOZSB(ip);

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        if ((vm_flags & VM_WRITE) && (zp->z_pflags &
            (ZFS_IMMUTABLE | ZFS_READONLY | ZFS_APPENDONLY))) {
                ZFS_EXIT(zsb);
                return (EPERM);
        }

        if ((vm_flags & (VM_READ | VM_EXEC)) &&
            (zp->z_pflags & ZFS_AV_QUARANTINED)) {
                ZFS_EXIT(zsb);
                return (EACCES);
        }

        if (off < 0 || len > MAXOFFSET_T - off) {
                ZFS_EXIT(zsb);
                return (ENXIO);
        }

        ZFS_EXIT(zsb);
        return (0);
}
EXPORT_SYMBOL(zfs_map);

/*
 * convoff - converts the given data (start, whence) to the
 * given whence.
 */
int
convoff(struct inode *ip, flock64_t *lckdat, int  whence, offset_t offset)
{
        vattr_t vap;
        int error;

        if ((lckdat->l_whence == 2) || (whence == 2)) {
                if ((error = zfs_getattr(ip, &vap, 0, CRED()) != 0))
                        return (error);
        }

        switch (lckdat->l_whence) {
        case 1:
                lckdat->l_start += offset;
                break;
        case 2:
                lckdat->l_start += vap.va_size;
                /* FALLTHRU */
        case 0:
                break;
        default:
                return (EINVAL);
        }

        if (lckdat->l_start < 0)
                return (EINVAL);

        switch (whence) {
        case 1:
                lckdat->l_start -= offset;
                break;
        case 2:
                lckdat->l_start -= vap.va_size;
                /* FALLTHRU */
        case 0:
                break;
        default:
                return (EINVAL);
        }

        lckdat->l_whence = (short)whence;
        return (0);
}

/*
 * Free or allocate space in a file.  Currently, this function only
 * supports the `F_FREESP' command.  However, this command is somewhat
 * misnamed, as its functionality includes the ability to allocate as
 * well as free space.
 *
 *      IN:     ip      - inode of file to free data in.
 *              cmd     - action to take (only F_FREESP supported).
 *              bfp     - section of file to free/alloc.
 *              flag    - current file open mode flags.
 *              offset  - current file offset.
 *              cr      - credentials of caller [UNUSED].
 *
 *      RETURN: 0 if success
 *              error code if failure
 *
 * Timestamps:
 *      ip - ctime|mtime updated
 */
/* ARGSUSED */
int
zfs_space(struct inode *ip, int cmd, flock64_t *bfp, int flag,
    offset_t offset, cred_t *cr)
{
        znode_t         *zp = ITOZ(ip);
        zfs_sb_t        *zsb = ITOZSB(ip);
        uint64_t        off, len;
        int             error;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        if (cmd != F_FREESP) {
                ZFS_EXIT(zsb);
                return (EINVAL);
        }

        if ((error = convoff(ip, bfp, 0, offset))) {
                ZFS_EXIT(zsb);
                return (error);
        }

        if (bfp->l_len < 0) {
                ZFS_EXIT(zsb);
                return (EINVAL);
        }

        /*
         * Permissions aren't checked on Solaris because on this OS
         * zfs_space() can only be called with an opened file handle.
         * On Linux we can get here through truncate_range() which
         * operates directly on inodes, so we need to check access rights.
         */
        if ((error = zfs_zaccess(zp, ACE_WRITE_DATA, 0, B_FALSE, cr))) {
                ZFS_EXIT(zsb);
                return (error);
        }

        off = bfp->l_start;
        len = bfp->l_len; /* 0 means from off to end of file */

        error = zfs_freesp(zp, off, len, flag, TRUE);

        ZFS_EXIT(zsb);
        return (error);
}
EXPORT_SYMBOL(zfs_space);

/*ARGSUSED*/
int
zfs_fid(struct inode *ip, fid_t *fidp)
{
        znode_t         *zp = ITOZ(ip);
        zfs_sb_t        *zsb = ITOZSB(ip);
        uint32_t        gen;
        uint64_t        gen64;
        uint64_t        object = zp->z_id;
        zfid_short_t    *zfid;
        int             size, i, error;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        if ((error = sa_lookup(zp->z_sa_hdl, SA_ZPL_GEN(zsb),
            &gen64, sizeof (uint64_t))) != 0) {
                ZFS_EXIT(zsb);
                return (error);
        }

        gen = (uint32_t)gen64;

        size = (zsb->z_parent != zsb) ? LONG_FID_LEN : SHORT_FID_LEN;
        if (fidp->fid_len < size) {
                fidp->fid_len = size;
                ZFS_EXIT(zsb);
                return (ENOSPC);
        }

        zfid = (zfid_short_t *)fidp;

        zfid->zf_len = size;

        for (i = 0; i < sizeof (zfid->zf_object); i++)
                zfid->zf_object[i] = (uint8_t)(object >> (8 * i));

        /* Must have a non-zero generation number to distinguish from .zfs */
        if (gen == 0)
                gen = 1;
        for (i = 0; i < sizeof (zfid->zf_gen); i++)
                zfid->zf_gen[i] = (uint8_t)(gen >> (8 * i));

        if (size == LONG_FID_LEN) {
                uint64_t        objsetid = dmu_objset_id(zsb->z_os);
                zfid_long_t     *zlfid;

                zlfid = (zfid_long_t *)fidp;

                for (i = 0; i < sizeof (zlfid->zf_setid); i++)
                        zlfid->zf_setid[i] = (uint8_t)(objsetid >> (8 * i));

                /* XXX - this should be the generation number for the objset */
                for (i = 0; i < sizeof (zlfid->zf_setgen); i++)
                        zlfid->zf_setgen[i] = 0;
        }

        ZFS_EXIT(zsb);
        return (0);
}
EXPORT_SYMBOL(zfs_fid);

/*ARGSUSED*/
int
zfs_getsecattr(struct inode *ip, vsecattr_t *vsecp, int flag, cred_t *cr)
{
        znode_t *zp = ITOZ(ip);
        zfs_sb_t *zsb = ITOZSB(ip);
        int error;
        boolean_t skipaclchk = (flag & ATTR_NOACLCHECK) ? B_TRUE : B_FALSE;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);
        error = zfs_getacl(zp, vsecp, skipaclchk, cr);
        ZFS_EXIT(zsb);

        return (error);
}
EXPORT_SYMBOL(zfs_getsecattr);

/*ARGSUSED*/
int
zfs_setsecattr(struct inode *ip, vsecattr_t *vsecp, int flag, cred_t *cr)
{
        znode_t *zp = ITOZ(ip);
        zfs_sb_t *zsb = ITOZSB(ip);
        int error;
        boolean_t skipaclchk = (flag & ATTR_NOACLCHECK) ? B_TRUE : B_FALSE;
        zilog_t *zilog = zsb->z_log;

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);

        error = zfs_setacl(zp, vsecp, skipaclchk, cr);

        if (zsb->z_os->os_sync == ZFS_SYNC_ALWAYS)
                zil_commit(zilog, 0);

        ZFS_EXIT(zsb);
        return (error);
}
EXPORT_SYMBOL(zfs_setsecattr);

#ifdef HAVE_UIO_ZEROCOPY
/*
 * Tunable, both must be a power of 2.
 *
 * zcr_blksz_min: the smallest read we may consider to loan out an arcbuf
 * zcr_blksz_max: if set to less than the file block size, allow loaning out of
 *              an arcbuf for a partial block read
 */
int zcr_blksz_min = (1 << 10);  /* 1K */
int zcr_blksz_max = (1 << 17);  /* 128K */

/*ARGSUSED*/
static int
zfs_reqzcbuf(struct inode *ip, enum uio_rw ioflag, xuio_t *xuio, cred_t *cr)
{
        znode_t *zp = ITOZ(ip);
        zfs_sb_t *zsb = ITOZSB(ip);
        int max_blksz = zsb->z_max_blksz;
        uio_t *uio = &xuio->xu_uio;
        ssize_t size = uio->uio_resid;
        offset_t offset = uio->uio_loffset;
        int blksz;
        int fullblk, i;
        arc_buf_t *abuf;
        ssize_t maxsize;
        int preamble, postamble;

        if (xuio->xu_type != UIOTYPE_ZEROCOPY)
                return (EINVAL);

        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);
        switch (ioflag) {
        case UIO_WRITE:
                /*
                 * Loan out an arc_buf for write if write size is bigger than
                 * max_blksz, and the file's block size is also max_blksz.
                 */
                blksz = max_blksz;
                if (size < blksz || zp->z_blksz != blksz) {
                        ZFS_EXIT(zsb);
                        return (EINVAL);
                }
                /*
                 * Caller requests buffers for write before knowing where the
                 * write offset might be (e.g. NFS TCP write).
                 */
                if (offset == -1) {
                        preamble = 0;
                } else {
                        preamble = P2PHASE(offset, blksz);
                        if (preamble) {
                                preamble = blksz - preamble;
                                size -= preamble;
                        }
                }

                postamble = P2PHASE(size, blksz);
                size -= postamble;

                fullblk = size / blksz;
                (void) dmu_xuio_init(xuio,
                    (preamble != 0) + fullblk + (postamble != 0));

                /*
                 * Have to fix iov base/len for partial buffers.  They
                 * currently represent full arc_buf's.
                 */
                if (preamble) {
                        /* data begins in the middle of the arc_buf */
                        abuf = dmu_request_arcbuf(sa_get_db(zp->z_sa_hdl),
                            blksz);
                        ASSERT(abuf);
                        (void) dmu_xuio_add(xuio, abuf,
                            blksz - preamble, preamble);
                }

                for (i = 0; i < fullblk; i++) {
                        abuf = dmu_request_arcbuf(sa_get_db(zp->z_sa_hdl),
                            blksz);
                        ASSERT(abuf);
                        (void) dmu_xuio_add(xuio, abuf, 0, blksz);
                }

                if (postamble) {
                        /* data ends in the middle of the arc_buf */
                        abuf = dmu_request_arcbuf(sa_get_db(zp->z_sa_hdl),
                            blksz);
                        ASSERT(abuf);
                        (void) dmu_xuio_add(xuio, abuf, 0, postamble);
                }
                break;
        case UIO_READ:
                /*
                 * Loan out an arc_buf for read if the read size is larger than
                 * the current file block size.  Block alignment is not
                 * considered.  Partial arc_buf will be loaned out for read.
                 */
                blksz = zp->z_blksz;
                if (blksz < zcr_blksz_min)
                        blksz = zcr_blksz_min;
                if (blksz > zcr_blksz_max)
                        blksz = zcr_blksz_max;
                /* avoid potential complexity of dealing with it */
                if (blksz > max_blksz) {
                        ZFS_EXIT(zsb);
                        return (EINVAL);
                }

                maxsize = zp->z_size - uio->uio_loffset;
                if (size > maxsize)
                        size = maxsize;

                if (size < blksz) {
                        ZFS_EXIT(zsb);
                        return (EINVAL);
                }
                break;
        default:
                ZFS_EXIT(zsb);
                return (EINVAL);
        }

        uio->uio_extflg = UIO_XUIO;
        XUIO_XUZC_RW(xuio) = ioflag;
        ZFS_EXIT(zsb);
        return (0);
}

/*ARGSUSED*/
static int
zfs_retzcbuf(struct inode *ip, xuio_t *xuio, cred_t *cr)
{
        int i;
        arc_buf_t *abuf;
        int ioflag = XUIO_XUZC_RW(xuio);

        ASSERT(xuio->xu_type == UIOTYPE_ZEROCOPY);

        i = dmu_xuio_cnt(xuio);
        while (i-- > 0) {
                abuf = dmu_xuio_arcbuf(xuio, i);
                /*
                 * if abuf == NULL, it must be a write buffer
                 * that has been returned in zfs_write().
                 */
                if (abuf)
                        dmu_return_arcbuf(abuf);
                ASSERT(abuf || ioflag == UIO_WRITE);
        }

        dmu_xuio_fini(xuio);
        return (0);
}
#endif /* HAVE_UIO_ZEROCOPY */

#if defined(_KERNEL) && defined(HAVE_SPL)
module_param(zfs_read_chunk_size, long, 0644);
MODULE_PARM_DESC(zfs_read_chunk_size, "Bytes to read per chunk");
#endif