dm-pcache: use int type to store negative error codes

Change the 'ret' variable from u32 to int to store negative error codes or
zero returned by cache_kset_close().

Storing the negative error codes in unsigned type, doesn't cause an issue
at runtime but it's ugly. Additionally, assigning negative error codes to
unsigned type may trigger a GCC warning when the -Wsign-conversion flag
is enabled.

No effect on runtime.

Signed-off-by: Qianfeng Rong <[email protected]>
Signed-off-by: Mikulas Patocka <[email protected]>

Author: qianfengrong

drivers/md/dm-pcache/cache_req.c

@@ -805,7 +805,8 @@ static int cache_write(struct pcache_cache *cache, struct pcache_request *pcache
 int cache_flush(struct pcache_cache *cache)
 {
 	struct pcache_cache_kset *kset;
-	u32 i, ret;
+	int ret;
+	u32 i;
 
 	for (i = 0; i < cache->n_ksets; i++) {
 		kset = get_kset(cache, i);