Re: [PATCH] btrfs: Improve error reporting in lookup_inline_extent_backref

[Nikolay Borisov <nborisov@suse.com>]

On 20.04.22 г. 18:54 ч., David Sterba wrote:
> On Wed, Apr 20, 2022 at 02:54:00PM +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 the in-memory
>> state of the offending leaf.
>>
>> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
>> ---
>>   fs/btrfs/extent-tree.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
>> index 963160a0c393..5a53bcfdca83 100644
>> --- a/fs/btrfs/extent-tree.c
>> +++ b/fs/btrfs/extent-tree.c
>> @@ -895,7 +895,10 @@ int lookup_inline_extent_backref(struct btrfs_trans_handle *trans,
>>   	err = -ENOENT;
>>   	while (1) {
>>   		if (ptr >= end) {
>> -			WARN_ON(ptr > end);
>> +			if (WARN_ON(ptr > end)) {
>> +				err = -EUCLEAN;
>> +				btrfs_print_leaf(path->slots[0]);
> 
> This gives a warning, the slots array does not contain the extent buffer
> pointer so this should have been path->nodes[0] but this is already in
> 'leaf', fixed.
> 

Ah you are right... should have been ->nodes[0] not slot...