Re: [PATCH 02/20] btrfs: handle invalid range and start in merge_extent_mapping()

Qu Wenruo
2024-01-25T03:53:09Z

On 2024/1/25 07:47, David Sterba wrote:
> Turn a BUG_ON to a properly handled error and update the error message
> in the caller. It is expected that @em_in and @start passed to
> btrfs_add_extent_mapping() overlap. Besides tests, the only caller
> btrfs_get_extent() makes sure this is true.
>
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
> fs/btrfs/extent_map.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
> index f170e7122e74..ac5e366d57b2 100644
> --- a/fs/btrfs/extent_map.c
> +++ b/fs/btrfs/extent_map.c
> @@ -539,7 +539,8 @@ static noinline int merge_extent_mapping(struct extent_map_tree *em_tree,
> u64 end;
> u64 start_diff;
>
> - BUG_ON(map_start < em->start || map_start >= extent_map_end(em));
> + if (map_start < em->start || map_start >= extent_map_end(em))
> + return -EINVAL;

Shouldn't we go -EUCLEAN?

This is not something we really expect to hit, as it normally means
something wrong with the extent map.

Thanks,
Qu

>
> if (existing->start > map_start) {
> next = existing;
> @@ -634,9 +635,9 @@ int btrfs_add_extent_mapping(struct btrfs_fs_info *fs_info,
> free_extent_map(em);
> *em_in = NULL;
> WARN_ONCE(ret,
> -"unexpected error %d: merge existing(start %llu len %llu) with em(start %llu len %llu)\n",
> - ret, existing->start, existing->len,
> - orig_start, orig_len);
> +"extent map merge error existing [%llu, %llu) with em [%llu, %llu) start %llu\n",
> + existing->start, existing->len,
> + orig_start, orig_len, start);
> }
> free_extent_map(existing);
> }