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

commit 536870071dbc4278264f59c9a2f5f447e584d139 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5b7768ccd20b57c4f15eca3f34290ebd3e9b63d3..17dd2a290e6120d68c4f0e9366657e11963bafa2 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2175,12 +2175,16 @@ 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);