Btrfs: fix metadata space leak on fixup worker failure to set range as delalloc

In the fixup worker, if we fail to mark the range as delalloc in the io
tree, we must release the previously reserved metadata, as well as update
the outstanding extents counter for the inode, otherwise we leak metadata
space.

In pratice we can't return an error from btrfs_set_extent_delalloc(),
which is just a wrapper around __set_extent_bit(), as for most errors
__set_extent_bit() does a BUG_ON() (or panics which hits a BUG_ON() as
well) and returning an -EEXIST error doesn't happen in this case since
the exclusive bits parameter always has a value of 0 through this code
path. Nevertheless, just fix the error handling in the fixup worker,
in case one day __set_extent_bit() can return an error to this code
path.

Fixes: f3038ee3a3f101 ("btrfs: Handle btrfs_set_extent_delalloc failure in fixup worker")
CC: stable@vger.kernel.org # 4.19+
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3315a6eb09a35dc0e13aa69324f08d3f379eb518..b943c9770533ab03a73c6ee78ef6d03a8da33b4c 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2254,12 +2254,16 @@ again:
                mapping_set_error(page->mapping, ret);
                end_extent_writepage(page, ret, page_start, page_end);
                ClearPageChecked(page);
-               goto out;
+               goto out_reserved;
        }
 
        ClearPageChecked(page);
        set_page_dirty(page);
+out_reserved:
        btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
+       if (ret)
+               btrfs_delalloc_release_space(inode, data_reserved, page_start,
+                                            PAGE_SIZE, true);
 out:
        unlock_extent_cached(&BTRFS_I(inode)->io_tree, page_start, page_end,
                             &cached_state);