staging: zcache: fix possible sleep under lock

zcache_new_pool() calls kmalloc() with GFP_KERNEL which has
__GFP_WAIT set.  However, zcache_new_pool() gets called on
a stack that holds the swap_lock spinlock, leading to a
possible sleep-with-lock situation. The lock is obtained
in enable_swap_info().

The patch replaces GFP_KERNEL with GFP_ATOMIC.

v2: replace with GFP_ATOMIC, not GFP_IOFS

Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/zcache/zcache-main.c

@@ -1668,7 +1668,7 @@ static int zcache_new_pool(uint16_t cli_id, uint32_t flags)
 	if (cli == NULL)
 		goto out;
 	atomic_inc(&cli->refcount);
-	pool = kmalloc(sizeof(struct tmem_pool), GFP_KERNEL);
+	pool = kmalloc(sizeof(struct tmem_pool), GFP_ATOMIC);
 	if (pool == NULL) {
 		pr_info("zcache: pool creation failed: out of memory\n");
 		goto out;