Re: [PATCH v5] btrfs: improve error reporting in lookup_inline_extent_backref

[Filipe Manana <fdmanana@kernel.org>]

On Fri, Apr 29, 2022 at 05:17:34PM +0300, Nikolay Borisov wrote:
> When iterating the backrefs in an extent item if the ptr to the
> 'current' backref record goes beyond the extent item a warning is
> generated and -ENOENT is returned. However what's more appropriate to
> debug such cases would be to return EUCLEAN and also print identifying
> information about the performed search as well as the current content of
> the leaf containing the possibly corrupted extent item.
> 
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>

Reviewed-by: Filipe Manana <fdmanana@suse.com>

Looks good now, thanks.

> ---
> 
> V5:
>  * Stop printing the key we are searching for as it was both wrong and redundant,
>  since we have the slot number printed anyway. (Filipe)
> 
> V4:
>  * Also print the value of 'parent' as it's pertinent when metadata inline backrefs
>  are being searched (Filipe)
>  * Print the leaf before printing the error message so that the latter is
>  not lost (Filipe)
> 
> V3:
>  * Fixed format for the btree slot
>  * Removed redundant argument passed to format string
> 
>  fs/btrfs/extent-tree.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 963160a0c393..cca89016f2b3 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -895,7 +895,14 @@ int lookup_inline_extent_backref(struct btrfs_trans_handle *trans,
>  	err = -ENOENT;
>  	while (1) {
>  		if (ptr >= end) {
> -			WARN_ON(ptr > end);
> +			if (ptr > end) {
> +				err = -EUCLEAN;
> +				btrfs_print_leaf(path->nodes[0]);
> +				btrfs_crit(fs_info,
> +"overrun extent record at slot %d while looking for inline extent for root %llu owner %llu offset %llu parent %llu",
> +				path->slots[0], root_objectid, owner, offset,
> +				parent);
> +			}
>  			break;
>  		}
>  		iref = (struct btrfs_extent_inline_ref *)ptr;
> --
> 2.25.1
>