Re: [PATCH 2/3] dm pcache: fix cache info indexing

[Dongsheng Yang]

在 12/5/2025 12:01 AM, Mikulas Patocka 写道:

On Thu, 4 Dec 2025, Dongsheng Yang wrote:

From: Li Chen <chenl...@chinatelecom.cn>

The on-media cache_info index used sizeof(struct) instead of the
4K metadata stride, so gc_percent updates from dmsetup message
were written between slots and lost after reboot. Use
PCACHE_CACHE_INFO_SIZE in get_cache_info_addr() and align
info_index with the slot returned by pcache_meta_find_latest().

Signed-off-by: Li Chen <chenl...@chinatelecom.cn>
Signed-off-by: Dongsheng Yang <dongsheng.y...@linux.dev>
---
  drivers/md/dm-pcache/cache.c | 8 ++++++--
  1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-pcache/cache.c b/drivers/md/dm-pcache/cache.c
index 9289c016b7c9..bcc4e509aa69 100644
--- a/drivers/md/dm-pcache/cache.c
+++ b/drivers/md/dm-pcache/cache.c
@@ -8,9 +8,11 @@

struct kmem_cache *key_cache; -static inline struct pcache_cache_info *get_cache_info_addr(struct pcache_cache *cache)

+static inline struct pcache_cache_info *
+get_cache_info_addr(struct pcache_cache *cache)
  {
-       return cache->cache_info_addr + cache->info_index;
+       return (struct pcache_cache_info *)((char *)cache->cache_info_addr +
+                                               (size_t)cache->info_index * 
PCACHE_CACHE_INFO_SIZE);
  }

static void cache_info_write(struct pcache_cache *cache)

@@ -49,6 +51,8 @@ static int cache_info_init(struct pcache_cache *cache, struct 
pcache_cache_optio
                        return -EINVAL;
                }

+ cache->info_index = ((char *)cache_info_addr - (char *)cache->cache_info_addr) / PCACHE_CACHE_INFO_SIZE;

+
                return 0;
        }

--

2.43.0

I already staged the patch below? Should I revert it and stage your new
patch?

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.c b/drivers/md/dm-pcache/cache.c
index d8e92367d947..9554d1158450 100644
--- a/drivers/md/dm-pcache/cache.c
+++ b/drivers/md/dm-pcache/cache.c
@@ -8,9 +8,11 @@

  struct kmem_cache *key_cache;

-static inline struct pcache_cache_info *get_cache_info_addr(struct 
pcache_cache *cache)
+static inline struct pcache_cache_info *
+get_cache_info_addr(struct pcache_cache *cache)
  {
-       return cache->cache_info_addr + cache->info_index;
+       return (struct pcache_cache_info *)((char *)cache->cache_info_addr
+
+                                               (size_t)cache->info_index * 
PCACHE_CACHE_INFO_SIZE);
  }

  static void cache_info_write(struct pcache_cache *cache)
@@ -40,7 +42,12 @@ static int cache_info_init(struct pcache_cache *cache,
struct pcache_cache_optio
         if (IS_ERR(cache_info_addr))
                 return PTR_ERR(cache_info_addr);

-       if (cache_info_addr) {
+    if (cache_info_addr) {
+               int index = ((char *)cache_info_addr - (char 
*)cache->cache_info_addr) /
+                               PCACHE_CACHE_INFO_SIZE;
+
+               cache->info_index = (index + 1) % PCACHE_META_INDEX_MAX;
+
                 if (opts->data_crc !=
                                 (cache->cache_info.flags & 
PCACHE_CACHE_FLAGS_DATA_CRC)) {
                         pcache_dev_err(pcache, "invalid option for data_crc: %s, 
expected: %s",