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

[Dongsheng Yang]

在 12/4/2025 11:59 PM, Mikulas Patocka 写道:

On Thu, 4 Dec 2025, Dongsheng Yang wrote:

From: Li Chen <chenl...@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 <chenl...@chinatelecom.cn>
Signed-off-by: Dongsheng Yang <dongsheng.y...@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);