Btrfs: use reserved space for creating a snapshot

While inserting dir index and updating inode for a snapshot, we'd
add delayed items which consume trans->block_rsv, if we don't have
any space reserved in this trans handle, we either just return or
reserve space again.

But before creating pending snapshots during committing transaction,
we've done a release on this trans handle, so we don't have space reserved
in it at this stage.

What we're using is block_rsv of pending snapshots which has already
reserved well enough space for both inserting dir index and updating
inode, so we need to set trans handle to indicate that we have space
now.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index a83d486cc70c8d0831bc32055c3b9b8451f580ba..4330433b7b4f5617edfd36ffb68a252e509328ea 100644 (file)
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1123,6 +1123,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 
        rsv = trans->block_rsv;
        trans->block_rsv = &pending->block_rsv;
+       trans->bytes_reserved = trans->block_rsv->reserved;
 
        dentry = pending->dentry;
        parent = dget_parent(dentry);
@@ -1276,6 +1277,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 fail:
        dput(parent);
        trans->block_rsv = rsv;
+       trans->bytes_reserved = 0;
 no_free_objectid:
        kfree(new_root_item);
 root_item_alloc_fail: