Add ddt_object_count() error handling
[zfs.git] / module / zfs / dsl_dataset.c
index 667aef3..21fdd08 100644 (file)
@@ -20,6 +20,8 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011 by Delphix. All rights reserved.
+ * Copyright (c) 2012, Joyent, Inc. All rights reserved.
  */
 
 #include <sys/dmu_objset.h>
@@ -28,6 +30,7 @@
 #include <sys/dsl_prop.h>
 #include <sys/dsl_synctask.h>
 #include <sys/dmu_traverse.h>
+#include <sys/dmu_impl.h>
 #include <sys/dmu_tx.h>
 #include <sys/arc.h>
 #include <sys/zio.h>
@@ -387,23 +390,29 @@ dsl_dataset_get_ref(dsl_pool_t *dp, uint64_t dsobj, void *tag,
 
        ds = dmu_buf_get_user(dbuf);
        if (ds == NULL) {
-               dsl_dataset_t *winner;
+               dsl_dataset_t *winner = NULL;
 
-               ds = kmem_zalloc(sizeof (dsl_dataset_t), KM_SLEEP);
+               ds = kmem_zalloc(sizeof (dsl_dataset_t), KM_PUSHPAGE);
                ds->ds_dbuf = dbuf;
                ds->ds_object = dsobj;
                ds->ds_phys = dbuf->db_data;
+               list_link_init(&ds->ds_synced_link);
 
                mutex_init(&ds->ds_lock, NULL, MUTEX_DEFAULT, NULL);
                mutex_init(&ds->ds_recvlock, NULL, MUTEX_DEFAULT, NULL);
                mutex_init(&ds->ds_opening_lock, NULL, MUTEX_DEFAULT, NULL);
-               rw_init(&ds->ds_rwlock, 0, 0, 0);
+               mutex_init(&ds->ds_sendstream_lock, NULL, MUTEX_DEFAULT, NULL);
+
+               rw_init(&ds->ds_rwlock, NULL, RW_DEFAULT, NULL);
                cv_init(&ds->ds_exclusive_cv, NULL, CV_DEFAULT, NULL);
 
                bplist_create(&ds->ds_pending_deadlist);
                dsl_deadlist_open(&ds->ds_deadlist,
                    mos, ds->ds_phys->ds_deadlist_obj);
 
+               list_create(&ds->ds_sendstreams, sizeof (dmu_sendarg_t),
+                   offsetof(dmu_sendarg_t, dsa_link));
+
                if (err == 0) {
                        err = dsl_dir_open_obj(dp,
                            ds->ds_phys->ds_dir_obj, NULL, ds, &ds->ds_dir);
@@ -905,69 +914,56 @@ dsl_dataset_create_sync(dsl_dir_t *pdd, const char *lastname,
        return (dsobj);
 }
 
-struct destroyarg {
-       dsl_sync_task_group_t *dstg;
-       char *snapname;
-       char *failed;
-       boolean_t defer;
-};
-
-static int
-dsl_snapshot_destroy_one(const char *name, void *arg)
-{
-       struct destroyarg *da = arg;
-       dsl_dataset_t *ds;
-       int err;
-       char *dsname;
-
-       dsname = kmem_asprintf("%s@%s", name, da->snapname);
-       err = dsl_dataset_own(dsname, B_TRUE, da->dstg, &ds);
-       strfree(dsname);
-       if (err == 0) {
-               struct dsl_ds_destroyarg *dsda;
-
-               dsl_dataset_make_exclusive(ds, da->dstg);
-               dsda = kmem_zalloc(sizeof (struct dsl_ds_destroyarg), KM_SLEEP);
-               dsda->ds = ds;
-               dsda->defer = da->defer;
-               dsl_sync_task_create(da->dstg, dsl_dataset_destroy_check,
-                   dsl_dataset_destroy_sync, dsda, da->dstg, 0);
-       } else if (err == ENOENT) {
-               err = 0;
-       } else {
-               (void) strcpy(da->failed, name);
-       }
-       return (err);
-}
-
 /*
- * Destroy 'snapname' in all descendants of 'fsname'.
+ * The snapshots must all be in the same pool.
  */
-#pragma weak dmu_snapshots_destroy = dsl_snapshots_destroy
 int
-dsl_snapshots_destroy(char *fsname, char *snapname, boolean_t defer)
+dmu_snapshots_destroy_nvl(nvlist_t *snaps, boolean_t defer, char *failed)
 {
        int err;
-       struct destroyarg da;
        dsl_sync_task_t *dst;
        spa_t *spa;
+       nvpair_t *pair;
+       dsl_sync_task_group_t *dstg;
 
-       err = spa_open(fsname, &spa, FTAG);
+       pair = nvlist_next_nvpair(snaps, NULL);
+       if (pair == NULL)
+               return (0);
+
+       err = spa_open(nvpair_name(pair), &spa, FTAG);
        if (err)
                return (err);
-       da.dstg = dsl_sync_task_group_create(spa_get_dsl(spa));
-       da.snapname = snapname;
-       da.failed = fsname;
-       da.defer = defer;
+       dstg = dsl_sync_task_group_create(spa_get_dsl(spa));
+
+       for (pair = nvlist_next_nvpair(snaps, NULL); pair != NULL;
+           pair = nvlist_next_nvpair(snaps, pair)) {
+               dsl_dataset_t *ds;
+               int err;
 
-       err = dmu_objset_find(fsname,
-           dsl_snapshot_destroy_one, &da, DS_FIND_CHILDREN);
+               err = dsl_dataset_own(nvpair_name(pair), B_TRUE, dstg, &ds);
+               if (err == 0) {
+                       struct dsl_ds_destroyarg *dsda;
+
+                       dsl_dataset_make_exclusive(ds, dstg);
+                       dsda = kmem_zalloc(sizeof (struct dsl_ds_destroyarg),
+                           KM_SLEEP);
+                       dsda->ds = ds;
+                       dsda->defer = defer;
+                       dsl_sync_task_create(dstg, dsl_dataset_destroy_check,
+                           dsl_dataset_destroy_sync, dsda, dstg, 0);
+               } else if (err == ENOENT) {
+                       err = 0;
+               } else {
+                       (void) strcpy(failed, nvpair_name(pair));
+                       break;
+               }
+       }
 
        if (err == 0)
-               err = dsl_sync_task_group_wait(da.dstg);
+               err = dsl_sync_task_group_wait(dstg);
 
-       for (dst = list_head(&da.dstg->dstg_tasks); dst;
-           dst = list_next(&da.dstg->dstg_tasks, dst)) {
+       for (dst = list_head(&dstg->dstg_tasks); dst;
+           dst = list_next(&dstg->dstg_tasks, dst)) {
                struct dsl_ds_destroyarg *dsda = dst->dst_arg1;
                dsl_dataset_t *ds = dsda->ds;
 
@@ -975,17 +971,17 @@ dsl_snapshots_destroy(char *fsname, char *snapname, boolean_t defer)
                 * Return the file system name that triggered the error
                 */
                if (dst->dst_err) {
-                       dsl_dataset_name(ds, fsname);
-                       *strchr(fsname, '@') = '\0';
+                       dsl_dataset_name(ds, failed);
                }
                ASSERT3P(dsda->rm_origin, ==, NULL);
-               dsl_dataset_disown(ds, da.dstg);
+               dsl_dataset_disown(ds, dstg);
                kmem_free(dsda, sizeof (struct dsl_ds_destroyarg));
        }
 
-       dsl_sync_task_group_destroy(da.dstg);
+       dsl_sync_task_group_destroy(dstg);
        spa_close(spa, FTAG);
        return (err);
+
 }
 
 static boolean_t
@@ -1054,7 +1050,7 @@ dsl_dataset_destroy(dsl_dataset_t *ds, void *tag, boolean_t defer)
        dsl_dir_t *dd;
        uint64_t obj;
        struct dsl_ds_destroyarg dsda = { 0 };
-       dsl_dataset_t dummy_ds = { 0 };
+       dsl_dataset_t *dummy_ds;
 
        dsda.ds = ds;
 
@@ -1074,8 +1070,9 @@ dsl_dataset_destroy(dsl_dataset_t *ds, void *tag, boolean_t defer)
        }
 
        dd = ds->ds_dir;
-       dummy_ds.ds_dir = dd;
-       dummy_ds.ds_object = ds->ds_object;
+       dummy_ds = kmem_zalloc(sizeof (dsl_dataset_t), KM_SLEEP);
+       dummy_ds->ds_dir = dd;
+       dummy_ds->ds_object = ds->ds_object;
 
        /*
         * Check for errors and mark this ds as inconsistent, in
@@ -1084,11 +1081,11 @@ dsl_dataset_destroy(dsl_dataset_t *ds, void *tag, boolean_t defer)
        err = dsl_sync_task_do(dd->dd_pool, dsl_dataset_destroy_begin_check,
            dsl_dataset_destroy_begin_sync, ds, NULL, 0);
        if (err)
-               goto out;
+               goto out_free;
 
        err = dmu_objset_from_ds(ds, &os);
        if (err)
-               goto out;
+               goto out_free;
 
        /*
         * remove the objects in open context, so that we won't
@@ -1103,7 +1100,7 @@ dsl_dataset_destroy(dsl_dataset_t *ds, void *tag, boolean_t defer)
                (void) dmu_free_object(os, obj);
        }
        if (err != ESRCH)
-               goto out;
+               goto out_free;
 
        /*
         * Only the ZIL knows how to free log blocks.
@@ -1121,8 +1118,7 @@ dsl_dataset_destroy(dsl_dataset_t *ds, void *tag, boolean_t defer)
         */
        if (ds->ds_phys->ds_bp.blk_fill == 0 &&
            dmu_objset_userused_enabled(os)) {
-               uint64_t count;
-
+               ASSERTV(uint64_t count);
                ASSERT(zap_count(os, DMU_USERUSED_OBJECT, &count) != 0 ||
                    count == 0);
                ASSERT(zap_count(os, DMU_GROUPUSED_OBJECT, &count) != 0 ||
@@ -1134,7 +1130,7 @@ dsl_dataset_destroy(dsl_dataset_t *ds, void *tag, boolean_t defer)
        rw_exit(&dd->dd_pool->dp_config_rwlock);
 
        if (err)
-               goto out;
+               goto out_free;
 
        /*
         * Blow away the dsl_dir + head dataset.
@@ -1150,7 +1146,7 @@ dsl_dataset_destroy(dsl_dataset_t *ds, void *tag, boolean_t defer)
                        err = dsl_dataset_origin_rm_prep(&dsda, tag);
                        if (err) {
                                dsl_dir_close(dd, FTAG);
-                               goto out;
+                               goto out_free;
                        }
                }
 
@@ -1158,7 +1154,7 @@ dsl_dataset_destroy(dsl_dataset_t *ds, void *tag, boolean_t defer)
                dsl_sync_task_create(dstg, dsl_dataset_destroy_check,
                    dsl_dataset_destroy_sync, &dsda, tag, 0);
                dsl_sync_task_create(dstg, dsl_dir_destroy_check,
-                   dsl_dir_destroy_sync, &dummy_ds, FTAG, 0);
+                   dsl_dir_destroy_sync, dummy_ds, FTAG, 0);
                err = dsl_sync_task_group_wait(dstg);
                dsl_sync_task_group_destroy(dstg);
 
@@ -1181,6 +1177,9 @@ dsl_dataset_destroy(dsl_dataset_t *ds, void *tag, boolean_t defer)
        /* if it is successful, dsl_dir_destroy_sync will close the dd */
        if (err)
                dsl_dir_close(dd, FTAG);
+
+out_free:
+       kmem_free(dummy_ds, sizeof (dsl_dataset_t));
 out:
        dsl_dataset_disown(ds, tag);
        return (err);
@@ -1232,6 +1231,19 @@ dsl_dataset_dirty(dsl_dataset_t *ds, dmu_tx_t *tx)
        }
 }
 
+boolean_t
+dsl_dataset_is_dirty(dsl_dataset_t *ds)
+{
+       int t;
+
+       for (t = 0; t < TXG_SIZE; t++) {
+               if (txg_list_member(&ds->ds_dir->dd_pool->dp_dirty_datasets,
+                   ds, t))
+                       return (B_TRUE);
+       }
+       return (B_FALSE);
+}
+
 /*
  * The unique space in the head dataset can be calculated by subtracting
  * the space used in the most recent snapshot, that is still being used
@@ -1495,8 +1507,8 @@ static void
 remove_from_next_clones(dsl_dataset_t *ds, uint64_t obj, dmu_tx_t *tx)
 {
        objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
-       uint64_t count;
        int err;
+       ASSERTV(uint64_t count);
 
        ASSERT(ds->ds_phys->ds_num_children >= 2);
        err = zap_remove_int(mos, ds->ds_phys->ds_next_clones_obj, obj, tx);
@@ -1921,7 +1933,7 @@ dsl_dataset_destroy_sync(void *arg1, void *tag, dmu_tx_t *tx)
            "dataset = %llu", ds->ds_object);
 
        if (ds->ds_phys->ds_next_clones_obj != 0) {
-               uint64_t count;
+               ASSERTV(uint64_t count);
                ASSERT(0 == zap_count(mos,
                    ds->ds_phys->ds_next_clones_obj, &count) && count == 0);
                VERIFY(0 == dmu_object_free(mos,
@@ -2146,10 +2158,59 @@ dsl_dataset_sync(dsl_dataset_t *ds, zio_t *zio, dmu_tx_t *tx)
        dmu_objset_sync(ds->ds_objset, zio, tx);
 }
 
+static void
+get_clones_stat(dsl_dataset_t *ds, nvlist_t *nv)
+{
+       uint64_t count = 0;
+       objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
+       zap_cursor_t zc;
+       zap_attribute_t za;
+       nvlist_t *propval;
+       nvlist_t *val;
+
+       rw_enter(&ds->ds_dir->dd_pool->dp_config_rwlock, RW_READER);
+       VERIFY(nvlist_alloc(&propval, NV_UNIQUE_NAME, KM_SLEEP) == 0);
+       VERIFY(nvlist_alloc(&val, NV_UNIQUE_NAME, KM_SLEEP) == 0);
+
+       /*
+        * There may me missing entries in ds_next_clones_obj
+        * due to a bug in a previous version of the code.
+        * Only trust it if it has the right number of entries.
+        */
+       if (ds->ds_phys->ds_next_clones_obj != 0) {
+               ASSERT3U(0, ==, zap_count(mos, ds->ds_phys->ds_next_clones_obj,
+                   &count));
+       }
+       if (count != ds->ds_phys->ds_num_children - 1) {
+               goto fail;
+       }
+       for (zap_cursor_init(&zc, mos, ds->ds_phys->ds_next_clones_obj);
+           zap_cursor_retrieve(&zc, &za) == 0;
+           zap_cursor_advance(&zc)) {
+               dsl_dataset_t *clone;
+               char buf[ZFS_MAXNAMELEN];
+               if (dsl_dataset_hold_obj(ds->ds_dir->dd_pool,
+                   za.za_first_integer, FTAG, &clone) != 0) {
+                       goto fail;
+               }
+               dsl_dir_name(clone->ds_dir, buf);
+               VERIFY(nvlist_add_boolean(val, buf) == 0);
+               dsl_dataset_rele(clone, FTAG);
+       }
+       zap_cursor_fini(&zc);
+       VERIFY(nvlist_add_nvlist(propval, ZPROP_VALUE, val) == 0);
+       VERIFY(nvlist_add_nvlist(nv, zfs_prop_to_name(ZFS_PROP_CLONES),
+           propval) == 0);
+fail:
+       nvlist_free(val);
+       nvlist_free(propval);
+       rw_exit(&ds->ds_dir->dd_pool->dp_config_rwlock);
+}
+
 void
 dsl_dataset_stats(dsl_dataset_t *ds, nvlist_t *nv)
 {
-       uint64_t refd, avail, uobjs, aobjs;
+       uint64_t refd, avail, uobjs, aobjs, ratio;
 
        dsl_dir_stats(ds->ds_dir, nv);
 
@@ -2176,6 +2237,32 @@ dsl_dataset_stats(dsl_dataset_t *ds, nvlist_t *nv)
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_DEFER_DESTROY,
            DS_IS_DEFER_DESTROY(ds) ? 1 : 0);
 
+       if (ds->ds_phys->ds_prev_snap_obj != 0) {
+               uint64_t written, comp, uncomp;
+               dsl_pool_t *dp = ds->ds_dir->dd_pool;
+               dsl_dataset_t *prev;
+               int err;
+
+               rw_enter(&dp->dp_config_rwlock, RW_READER);
+               err = dsl_dataset_hold_obj(dp,
+                   ds->ds_phys->ds_prev_snap_obj, FTAG, &prev);
+               rw_exit(&dp->dp_config_rwlock);
+               if (err == 0) {
+                       err = dsl_dataset_space_written(prev, ds, &written,
+                           &comp, &uncomp);
+                       dsl_dataset_rele(prev, FTAG);
+                       if (err == 0) {
+                               dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_WRITTEN,
+                                   written);
+                       }
+               }
+       }
+
+       ratio = ds->ds_phys->ds_compressed_bytes == 0 ? 100 :
+           (ds->ds_phys->ds_uncompressed_bytes * 100 /
+           ds->ds_phys->ds_compressed_bytes);
+       dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_REFRATIO, ratio);
+
        if (ds->ds_phys->ds_next_snap_obj) {
                /*
                 * This is a snapshot; override the dd's space used with
@@ -2183,10 +2270,9 @@ dsl_dataset_stats(dsl_dataset_t *ds, nvlist_t *nv)
                 */
                dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USED,
                    ds->ds_phys->ds_unique_bytes);
-               dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_COMPRESSRATIO,
-                   ds->ds_phys->ds_compressed_bytes == 0 ? 100 :
-                   (ds->ds_phys->ds_uncompressed_bytes * 100 /
-                   ds->ds_phys->ds_compressed_bytes));
+               dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_COMPRESSRATIO, ratio);
+
+               get_clones_stat(ds, nv);
        }
 }
 
@@ -2251,7 +2337,7 @@ dsl_dataset_space(dsl_dataset_t *ds,
 boolean_t
 dsl_dataset_modified_since_lastsnap(dsl_dataset_t *ds)
 {
-       dsl_pool_t *dp = ds->ds_dir->dd_pool;
+       ASSERTV(dsl_pool_t *dp = ds->ds_dir->dd_pool);
 
        ASSERT(RW_LOCK_HELD(&dp->dp_config_rwlock) ||
            dsl_pool_sync_context(dp));
@@ -2522,7 +2608,6 @@ struct promotearg {
 };
 
 static int snaplist_space(list_t *l, uint64_t mintxg, uint64_t *spacep);
-static boolean_t snaplist_unstable(list_t *l);
 
 static int
 dsl_dataset_promote_check(void *arg1, void *arg2, dmu_tx_t *tx)
@@ -2923,10 +3008,11 @@ dsl_dataset_promote(const char *name, char *conflsnap)
        dsl_dir_t *dd;
        dsl_pool_t *dp;
        dmu_object_info_t doi;
-       struct promotearg pa = { 0 };
+       struct promotearg pa;
        struct promotenode *snap;
        int err;
 
+       bzero(&pa, sizeof(struct promotearg));
        err = dsl_dataset_hold(name, FTAG, &ds);
        if (err)
                return (err);
@@ -3282,6 +3368,8 @@ dsl_dataset_check_quota(dsl_dataset_t *ds, boolean_t check_quota,
                        error = ERESTART;
                else
                        error = EDQUOT;
+
+               DMU_TX_STAT_BUMP(dmu_tx_quota);
        }
        mutex_exit(&ds->ds_lock);
 
@@ -3327,10 +3415,6 @@ dsl_dataset_set_quota_sync(void *arg1, void *arg2, dmu_tx_t *tx)
        if (ds->ds_quota != effective_value) {
                dmu_buf_will_dirty(ds->ds_dbuf, tx);
                ds->ds_quota = effective_value;
-
-               spa_history_log_internal(LOG_DS_REFQUOTA,
-                   ds->ds_dir->dd_pool->dp_spa, tx, "%lld dataset = %llu ",
-                   (longlong_t)ds->ds_quota, ds->ds_object);
        }
 }
 
@@ -3434,10 +3518,6 @@ dsl_dataset_set_reservation_sync(void *arg1, void *arg2, dmu_tx_t *tx)
 
        dsl_dir_diduse_space(ds->ds_dir, DD_USED_REFRSRV, delta, 0, 0, tx);
        mutex_exit(&ds->ds_dir->dd_lock);
-
-       spa_history_log_internal(LOG_DS_REFRESERV,
-           ds->ds_dir->dd_pool->dp_spa, tx, "%lld dataset = %llu",
-           (longlong_t)effective_value, ds->ds_object);
 }
 
 int
@@ -3786,6 +3866,11 @@ dsl_dataset_user_release_sync(void *arg1, void *tag, dmu_tx_t *tx)
        VERIFY(error == 0 || error == ENOENT);
        zapobj = ds->ds_phys->ds_userrefs_obj;
        VERIFY(0 == zap_remove(mos, zapobj, ra->htag, tx));
+
+       spa_history_log_internal(LOG_DS_USER_RELEASE,
+           dp->dp_spa, tx, "<%s> %lld dataset = %llu",
+           ra->htag, (longlong_t)refs, dsobj);
+
        if (ds->ds_userrefs == 0 && ds->ds_phys->ds_num_children == 1 &&
            DS_IS_DEFER_DESTROY(ds)) {
                struct dsl_ds_destroyarg dsda = {0};
@@ -3796,10 +3881,6 @@ dsl_dataset_user_release_sync(void *arg1, void *tag, dmu_tx_t *tx)
                /* We already did the destroy_check */
                dsl_dataset_destroy_sync(&dsda, tag, tx);
        }
-
-       spa_history_log_internal(LOG_DS_USER_RELEASE,
-           dp->dp_spa, tx, "<%s> %lld dataset = %llu",
-           ra->htag, (longlong_t)refs, dsobj);
 }
 
 static int
@@ -4013,7 +4094,7 @@ dsl_dataset_get_holds(const char *dsname, nvlist_t **nvp)
 }
 
 /*
- * Note, this fuction is used as the callback for dmu_objset_find().  We
+ * Note, this function is used as the callback for dmu_objset_find().  We
  * always return 0 so that we will continue to find and process
  * inconsistent datasets, even if we encounter an error trying to
  * process one of them.
@@ -4032,3 +4113,202 @@ dsl_destroy_inconsistent(const char *dsname, void *arg)
        }
        return (0);
 }
+
+
+/*
+ * Return (in *usedp) the amount of space written in new that is not
+ * present in oldsnap.  New may be a snapshot or the head.  Old must be
+ * a snapshot before new, in new's filesystem (or its origin).  If not then
+ * fail and return EINVAL.
+ *
+ * The written space is calculated by considering two components:  First, we
+ * ignore any freed space, and calculate the written as new's used space
+ * minus old's used space.  Next, we add in the amount of space that was freed
+ * between the two snapshots, thus reducing new's used space relative to old's.
+ * Specifically, this is the space that was born before old->ds_creation_txg,
+ * and freed before new (ie. on new's deadlist or a previous deadlist).
+ *
+ * space freed                         [---------------------]
+ * snapshots                       ---O-------O--------O-------O------
+ *                                         oldsnap            new
+ */
+int
+dsl_dataset_space_written(dsl_dataset_t *oldsnap, dsl_dataset_t *new,
+    uint64_t *usedp, uint64_t *compp, uint64_t *uncompp)
+{
+       int err = 0;
+       uint64_t snapobj;
+       dsl_pool_t *dp = new->ds_dir->dd_pool;
+
+       *usedp = 0;
+       *usedp += new->ds_phys->ds_used_bytes;
+       *usedp -= oldsnap->ds_phys->ds_used_bytes;
+
+       *compp = 0;
+       *compp += new->ds_phys->ds_compressed_bytes;
+       *compp -= oldsnap->ds_phys->ds_compressed_bytes;
+
+       *uncompp = 0;
+       *uncompp += new->ds_phys->ds_uncompressed_bytes;
+       *uncompp -= oldsnap->ds_phys->ds_uncompressed_bytes;
+
+       rw_enter(&dp->dp_config_rwlock, RW_READER);
+       snapobj = new->ds_object;
+       while (snapobj != oldsnap->ds_object) {
+               dsl_dataset_t *snap;
+               uint64_t used, comp, uncomp;
+
+               err = dsl_dataset_hold_obj(dp, snapobj, FTAG, &snap);
+               if (err != 0)
+                       break;
+
+               if (snap->ds_phys->ds_prev_snap_txg ==
+                   oldsnap->ds_phys->ds_creation_txg) {
+                       /*
+                        * The blocks in the deadlist can not be born after
+                        * ds_prev_snap_txg, so get the whole deadlist space,
+                        * which is more efficient (especially for old-format
+                        * deadlists).  Unfortunately the deadlist code
+                        * doesn't have enough information to make this
+                        * optimization itself.
+                        */
+                       dsl_deadlist_space(&snap->ds_deadlist,
+                           &used, &comp, &uncomp);
+               } else {
+                       dsl_deadlist_space_range(&snap->ds_deadlist,
+                           0, oldsnap->ds_phys->ds_creation_txg,
+                           &used, &comp, &uncomp);
+               }
+               *usedp += used;
+               *compp += comp;
+               *uncompp += uncomp;
+
+               /*
+                * If we get to the beginning of the chain of snapshots
+                * (ds_prev_snap_obj == 0) before oldsnap, then oldsnap
+                * was not a snapshot of/before new.
+                */
+               snapobj = snap->ds_phys->ds_prev_snap_obj;
+               dsl_dataset_rele(snap, FTAG);
+               if (snapobj == 0) {
+                       err = EINVAL;
+                       break;
+               }
+
+       }
+       rw_exit(&dp->dp_config_rwlock);
+       return (err);
+}
+
+/*
+ * Return (in *usedp) the amount of space that will be reclaimed if firstsnap,
+ * lastsnap, and all snapshots in between are deleted.
+ *
+ * blocks that would be freed            [---------------------------]
+ * snapshots                       ---O-------O--------O-------O--------O
+ *                                        firstsnap        lastsnap
+ *
+ * This is the set of blocks that were born after the snap before firstsnap,
+ * (birth > firstsnap->prev_snap_txg) and died before the snap after the
+ * last snap (ie, is on lastsnap->ds_next->ds_deadlist or an earlier deadlist).
+ * We calculate this by iterating over the relevant deadlists (from the snap
+ * after lastsnap, backward to the snap after firstsnap), summing up the
+ * space on the deadlist that was born after the snap before firstsnap.
+ */
+int
+dsl_dataset_space_wouldfree(dsl_dataset_t *firstsnap,
+    dsl_dataset_t *lastsnap,
+    uint64_t *usedp, uint64_t *compp, uint64_t *uncompp)
+{
+       int err = 0;
+       uint64_t snapobj;
+       dsl_pool_t *dp = firstsnap->ds_dir->dd_pool;
+
+       ASSERT(dsl_dataset_is_snapshot(firstsnap));
+       ASSERT(dsl_dataset_is_snapshot(lastsnap));
+
+       /*
+        * Check that the snapshots are in the same dsl_dir, and firstsnap
+        * is before lastsnap.
+        */
+       if (firstsnap->ds_dir != lastsnap->ds_dir ||
+           firstsnap->ds_phys->ds_creation_txg >
+           lastsnap->ds_phys->ds_creation_txg)
+               return (EINVAL);
+
+       *usedp = *compp = *uncompp = 0;
+
+       rw_enter(&dp->dp_config_rwlock, RW_READER);
+       snapobj = lastsnap->ds_phys->ds_next_snap_obj;
+       while (snapobj != firstsnap->ds_object) {
+               dsl_dataset_t *ds;
+               uint64_t used, comp, uncomp;
+
+               err = dsl_dataset_hold_obj(dp, snapobj, FTAG, &ds);
+               if (err != 0)
+                       break;
+
+               dsl_deadlist_space_range(&ds->ds_deadlist,
+                   firstsnap->ds_phys->ds_prev_snap_txg, UINT64_MAX,
+                   &used, &comp, &uncomp);
+               *usedp += used;
+               *compp += comp;
+               *uncompp += uncomp;
+
+               snapobj = ds->ds_phys->ds_prev_snap_obj;
+               ASSERT3U(snapobj, !=, 0);
+               dsl_dataset_rele(ds, FTAG);
+       }
+       rw_exit(&dp->dp_config_rwlock);
+       return (err);
+}
+
+#if defined(_KERNEL) && defined(HAVE_SPL)
+EXPORT_SYMBOL(dmu_snapshots_destroy_nvl);
+EXPORT_SYMBOL(dsl_dataset_hold);
+EXPORT_SYMBOL(dsl_dataset_hold_obj);
+EXPORT_SYMBOL(dsl_dataset_own);
+EXPORT_SYMBOL(dsl_dataset_own_obj);
+EXPORT_SYMBOL(dsl_dataset_name);
+EXPORT_SYMBOL(dsl_dataset_rele);
+EXPORT_SYMBOL(dsl_dataset_disown);
+EXPORT_SYMBOL(dsl_dataset_drop_ref);
+EXPORT_SYMBOL(dsl_dataset_tryown);
+EXPORT_SYMBOL(dsl_dataset_make_exclusive);
+EXPORT_SYMBOL(dsl_dataset_create_sync);
+EXPORT_SYMBOL(dsl_dataset_create_sync_dd);
+EXPORT_SYMBOL(dsl_dataset_destroy);
+EXPORT_SYMBOL(dsl_dataset_destroy_check);
+EXPORT_SYMBOL(dsl_dataset_destroy_sync);
+EXPORT_SYMBOL(dsl_dataset_snapshot_check);
+EXPORT_SYMBOL(dsl_dataset_snapshot_sync);
+EXPORT_SYMBOL(dsl_dataset_rename);
+EXPORT_SYMBOL(dsl_dataset_promote);
+EXPORT_SYMBOL(dsl_dataset_clone_swap);
+EXPORT_SYMBOL(dsl_dataset_user_hold);
+EXPORT_SYMBOL(dsl_dataset_user_release);
+EXPORT_SYMBOL(dsl_dataset_user_release_tmp);
+EXPORT_SYMBOL(dsl_dataset_get_holds);
+EXPORT_SYMBOL(dsl_dataset_get_blkptr);
+EXPORT_SYMBOL(dsl_dataset_set_blkptr);
+EXPORT_SYMBOL(dsl_dataset_get_spa);
+EXPORT_SYMBOL(dsl_dataset_modified_since_lastsnap);
+EXPORT_SYMBOL(dsl_dataset_space_written);
+EXPORT_SYMBOL(dsl_dataset_space_wouldfree);
+EXPORT_SYMBOL(dsl_dataset_sync);
+EXPORT_SYMBOL(dsl_dataset_block_born);
+EXPORT_SYMBOL(dsl_dataset_block_kill);
+EXPORT_SYMBOL(dsl_dataset_block_freeable);
+EXPORT_SYMBOL(dsl_dataset_prev_snap_txg);
+EXPORT_SYMBOL(dsl_dataset_dirty);
+EXPORT_SYMBOL(dsl_dataset_stats);
+EXPORT_SYMBOL(dsl_dataset_fast_stat);
+EXPORT_SYMBOL(dsl_dataset_space);
+EXPORT_SYMBOL(dsl_dataset_fsid_guid);
+EXPORT_SYMBOL(dsl_dsobj_to_dsname);
+EXPORT_SYMBOL(dsl_dataset_check_quota);
+EXPORT_SYMBOL(dsl_dataset_set_quota);
+EXPORT_SYMBOL(dsl_dataset_set_quota_sync);
+EXPORT_SYMBOL(dsl_dataset_set_reservation);
+EXPORT_SYMBOL(dsl_destroy_inconsistent);
+#endif