dm-bufio: fix warnings about duplicate slab caches

The commit 4c39529 adds a warning about duplicate cache names if
CONFIG_DEBUG_VM is selected. These warnings are triggered by the dm-bufio
code. The dm-bufio code allocates a slab cache with each client. It is
not possible to preallocate the caches in the module init function
because the size of auxiliary per-buffer data is not known at this point.

So, this commit changes dm-bufio so that it appends a unique atomic value
to the cache name, to avoid the warnings.

Signed-off-by: Mikulas Patocka <[email protected]>
Fixes: 4c39529 ("slab: Warn on duplicate cache names when DEBUG_VM=y")

Author: Mikulas Patocka

drivers/md/dm-bufio.c

@@ -2471,7 +2471,8 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
 	int r;
 	unsigned int num_locks;
 	struct dm_bufio_client *c;
-	char slab_name[27];
+	char slab_name[64];
+	static atomic_t seqno = ATOMIC_INIT(0);
 
 	if (!block_size || block_size & ((1 << SECTOR_SHIFT) - 1)) {
 		DMERR("%s: block size not specified or is not multiple of 512b", __func__);
@@ -2522,7 +2523,8 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
 	    (block_size < PAGE_SIZE || !is_power_of_2(block_size))) {
 		unsigned int align = min(1U << __ffs(block_size), (unsigned int)PAGE_SIZE);
 
-		snprintf(slab_name, sizeof(slab_name), "dm_bufio_cache-%u", block_size);
+		snprintf(slab_name, sizeof(slab_name), "dm_bufio_cache-%u-%u",
+					block_size, atomic_inc_return(&seqno));
 		c->slab_cache = kmem_cache_create(slab_name, block_size, align,
 						  SLAB_RECLAIM_ACCOUNT, NULL);
 		if (!c->slab_cache) {
@@ -2531,9 +2533,11 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
 		}
 	}
 	if (aux_size)
-		snprintf(slab_name, sizeof(slab_name), "dm_bufio_buffer-%u", aux_size);
+		snprintf(slab_name, sizeof(slab_name), "dm_bufio_buffer-%u-%u",
+					aux_size, atomic_inc_return(&seqno));
 	else
-		snprintf(slab_name, sizeof(slab_name), "dm_bufio_buffer");
+		snprintf(slab_name, sizeof(slab_name), "dm_bufio_buffer-%u",
+					atomic_inc_return(&seqno));
 	c->slab_buffer = kmem_cache_create(slab_name, sizeof(struct dm_buffer) + aux_size,
 					   0, SLAB_RECLAIM_ACCOUNT, NULL);
 	if (!c->slab_buffer) {