Re: [PATCH 3/3] dm pcache: fix segment info indexing

[Dongsheng Yang <dongsheng.yang@linux.dev>]

在 12/4/2025 11:59 PM, Mikulas Patocka 写道:
>
> On Thu, 4 Dec 2025, Dongsheng Yang wrote:
>
>> From: Li Chen <chenl311@chinatelecom.cn>
>>
>> Segment info indexing also used sizeof(struct) instead of the
>> 4K metadata stride, so info_index could point between slots and
>> subsequent writes would advance incorrectly. Derive info_index
>> from the pointer returned by the segment meta search using
>> PCACHE_SEG_INFO_SIZE and advance to the next slot for future
>> updates.
>>
>> Signed-off-by: Li Chen <chenl311@chinatelecom.cn>
>> Signed-off-by: Dongsheng Yang <dongsheng.yang@linux.dev>
>> ---
>>   drivers/md/dm-pcache/cache_segment.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/md/dm-pcache/cache_segment.c b/drivers/md/dm-pcache/cache_segment.c
>> index ae57cc261422..9d92e2b067ed 100644
>> --- a/drivers/md/dm-pcache/cache_segment.c
>> +++ b/drivers/md/dm-pcache/cache_segment.c
>> @@ -56,7 +56,10 @@ static int cache_seg_info_load(struct pcache_cache_segment *cache_seg)
>>   		ret = -EIO;
>>   		goto out;
>>   	}
>> -	cache_seg->info_index = cache_seg_info_addr - cache_seg_info_addr_base;
>> +
>> +	cache_seg->info_index =
>> +		((char *)cache_seg_info_addr - (char *)cache_seg_info_addr_base) /
>> +		PCACHE_SEG_INFO_SIZE;
>>   out:
>>   	mutex_unlock(&cache_seg->info_lock);
>>   
> Hi
>
> I already staged the patch below. Which patch is valid? Your new patch or
> the patch that I staged?


Yes, please revert it, I will send a v2 patchset, please pick the v2 patch.


Thanx


>
> Mikulas
>
>
>
> diff --git a/drivers/md/dm-pcache/cache_segment.c
> b/drivers/md/dm-pcache/cache_segment.c
> index f0b58980806e..0b4bb08011ce 100644
> --- a/drivers/md/dm-pcache/cache_segment.c
> +++ b/drivers/md/dm-pcache/cache_segment.c
> @@ -56,7 +56,11 @@ static int cache_seg_info_load(struct
> pcache_cache_segment *cache_seg)
>                  ret = -EIO;
>                  goto out;
>          }
> -       cache_seg->info_index = cache_seg_info_addr - cache_seg_info_addr_base;
> +
> +       cache_seg->info_index =
> +               ((char *)cache_seg_info_addr - (char *)cache_seg_info_addr_base) /
> +               PCACHE_SEG_INFO_SIZE;
> +       cache_seg->info_index = (cache_seg->info_index + 1) % PCACHE_META_INDEX_MAX;
>   out:
>          mutex_unlock(&cache_seg->info_lock);
>
>