btrfs: fix deadlock when writing out space cache

If we fail to prepare our pages for whatever reason (out of memory in
our case) we need to make sure to drop the block_group->data_rwsem,
otherwise hilarity ensues.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add label and use existing unlocking code ]
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index cdc9f4015ec36c08688a81bb1ba2bf657a9845ef..4426d1c73e50f1d1b1105a182d9c982a28b8ff08 100644 (file)
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1264,7 +1264,7 @@ static int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
        /* Lock all pages first so we can lock the extent safely. */
        ret = io_ctl_prepare_pages(io_ctl, inode, 0);
        if (ret)
-               goto out;
+               goto out_unlock;
 
        lock_extent_bits(&BTRFS_I(inode)->io_tree, 0, i_size_read(inode) - 1,
                         &cached_state);
@@ -1358,6 +1358,7 @@ out_nospc_locked:
 out_nospc:
        cleanup_write_cache_enospc(inode, io_ctl, &cached_state);
 
+out_unlock:
        if (block_group && (block_group->flags & BTRFS_BLOCK_GROUP_DATA))
                up_write(&block_group->data_rwsem);