Align DISCARD requests on zvols.

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

diff --git a/module/zfs/zvol.c b/module/zfs/zvol.c
index 5668e1d..b07476c 100644 (file)
--- a/module/zfs/zvol.c
+++ b/module/zfs/zvol.c
@@ -597,8 +597,8 @@ zvol_discard(void *arg)
        struct request *req = (struct request *)arg;
        struct request_queue *q = req->q;
        zvol_state_t *zv = q->queuedata;
-       uint64_t offset = blk_rq_pos(req) << 9;
-       uint64_t size = blk_rq_bytes(req);
+       uint64_t start = blk_rq_pos(req) << 9;
+       uint64_t end = start + blk_rq_bytes(req);
        int error;
        rl_t *rl;
 
@@ -610,19 +610,28 @@ zvol_discard(void *arg)
        ASSERT(!(current->flags & PF_NOFS));
        current->flags |= PF_NOFS;
 
-       if (offset + size > zv->zv_volsize) {
-               blk_end_request(req, -EIO, size);
+       if (end > zv->zv_volsize) {
+               blk_end_request(req, -EIO, blk_rq_bytes(req));
                goto out;
        }
 
-       if (size == 0) {
-               blk_end_request(req, 0, size);
+       /*
+        * Align the request to volume block boundaries. If we don't,
+        * then this will force dnode_free_range() to zero out the
+        * unaligned parts, which is slow (read-modify-write) and
+        * useless since we are not freeing any space by doing so.
+        */
+       start = P2ROUNDUP(start, zv->zv_volblocksize);
+       end = P2ALIGN(end, zv->zv_volblocksize);
+
+       if (start >= end) {
+               blk_end_request(req, 0, blk_rq_bytes(req));
                goto out;
        }
 
-       rl = zfs_range_lock(&zv->zv_znode, offset, size, RL_WRITER);
+       rl = zfs_range_lock(&zv->zv_znode, start, end - start, RL_WRITER);
 
-       error = dmu_free_long_range(zv->zv_objset, ZVOL_OBJ, offset, size);
+       error = dmu_free_long_range(zv->zv_objset, ZVOL_OBJ, start, end - start);
 
        /*
         * TODO: maybe we should add the operation to the log.
@@ -630,7 +639,7 @@ zvol_discard(void *arg)
 
        zfs_range_unlock(rl);
 
-       blk_end_request(req, -error, size);
+       blk_end_request(req, -error, blk_rq_bytes(req));
 out:
        current->flags &= ~PF_NOFS;
 }