Re: [PATCH 2/2] dm pcache: fix segment info indexing

[Dongsheng Yang]

在 12/2/2025 8:11 PM, Li Chen 写道:

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>
---
  drivers/md/dm-pcache/cache_segment.c | 6 +++++-
  1 file changed, 5 insertions(+), 1 deletion(-)

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;

Don't advance info_index at init stage.

  out:
        mutex_unlock(&cache_seg->info_lock);