Re: [bug report] dm-pcache: add persistent cache target in device-mapper

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

在 8/18/2025 5:52 PM, Dan Carpenter 写道:
> Hello Dongsheng Yang,
>
> Commit 6fb8fbbaf147 ("dm-pcache: add persistent cache target in
> device-mapper") from Aug 12, 2025 (linux-next), leads to the
> following Smatch static checker warning:
>
> 	drivers/md/dm-pcache/cache_req.c:60 cache_data_alloc()
> 	error: uninitialized symbol 'to_alloc'.


Hi Dan,

     Thanx for your report, I did fix it in my local tree, and testing 
is running now. If all tests pass, I will send the patch out tomorrow.


Thanx

Dongsheng

>
> drivers/md/dm-pcache/cache_req.c
>      36 static int cache_data_alloc(struct pcache_cache *cache, struct pcache_cache_key *key)
>      37 {
>      38         struct pcache_cache_data_head *data_head;
>      39         struct pcache_cache_pos *head_pos;
>      40         struct pcache_cache_segment *cache_seg;
>      41         u32 seg_remain;
>      42         u32 allocated = 0, to_alloc;
>      43         int ret = 0;
>      44
>      45         preempt_disable();
>      46         data_head = get_data_head(cache);
>      47 again:
>      48         if (!data_head->head_pos.cache_seg) {
>      49                 seg_remain = 0;
>
> to_alloc isn't initialized on this path.
>
>      50         } else {
>      51                 cache_pos_copy(&key->cache_pos, &data_head->head_pos);
>      52                 key->seg_gen = key->cache_pos.cache_seg->gen;
>      53
>      54                 head_pos = &data_head->head_pos;
>      55                 cache_seg = head_pos->cache_seg;
>      56                 seg_remain = cache_seg_remain(head_pos);
>      57                 to_alloc = key->len - allocated;
>      58         }
>      59
> --> 60         if (seg_remain > to_alloc) {
>                                  ^^^^^^^^
>
>      61                 /* If remaining space in segment is sufficient for the cache key, allocate it. */
>      62                 cache_pos_advance(head_pos, to_alloc);
>      63                 allocated += to_alloc;
>      64                 cache_seg_get(cache_seg);
>      65         } else if (seg_remain) {
>      66                 /* If remaining space is not enough, allocate the remaining space and adjust the cache key length. */
>      67                 cache_pos_advance(head_pos, seg_remain);
>      68                 key->len = seg_remain;
>      69
>      70                 /* Get for key: obtain a reference to the cache segment for the key. */
>      71                 cache_seg_get(cache_seg);
>      72                 /* Put for head_pos->cache_seg: release the reference for the current head's segment. */
>      73                 cache_seg_put(head_pos->cache_seg);
>      74                 head_pos->cache_seg = NULL;
>      75         } else {
>      76                 /* Initialize a new data head if no segment is available. */
>      77                 ret = cache_data_head_init(cache);
>      78                 if (ret)
>      79                         goto out;
>      80
>      81                 goto again;
>      82         }
>      83
>      84 out:
>      85         preempt_enable();
>      86
>      87         return ret;
>      88 }
>
> regards,
> dan carpenter