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

[Dongsheng Yang]

在 12/3/2025 1:57 PM, Dongsheng Yang 写道:

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.


ignore this incorrect comment, info_index means next slot, we need to 
advance it here.


  out:
      mutex_unlock(&cache_seg->info_lock);