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

[Dan Carpenter <dan.carpenter@linaro.org>]

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'.

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