Patch "mm/zswap: provide unique zpool name" has been added to the 4.5-stable tree

This is a note to let you know that I've just added the patch titled

mm/zswap: provide unique zpool name

to the 4.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mm-zswap-provide-unique-zpool-name.patch
and it can be found in the queue-4.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Dan Streetman <[email protected]>
Date: Thu, 5 May 2016 16:22:23 -0700
Subject: mm/zswap: provide unique zpool name

From: Dan Streetman <[email protected]>

commit 32a4e169039927bfb6ee9f0ccbbe3a8aaf13a4bc upstream.

Instead of using "zswap" as the name for all zpools created, add an atomic counter and use "zswap%x" with the counter number for each zpool created, to provide a unique name for each new zpool.

As zsmalloc, one of the zpool implementations, requires/expects a unique name for each pool created, zswap should provide a unique name. The zsmalloc pool creation does not fail if a new pool with a conflicting name is created, unless CONFIG_ZSMALLOC_STAT is enabled; in that case, zsmalloc pool creation fails with -ENOMEM. Then zswap will be unable to change its compressor parameter if its zpool is zsmalloc; it also will be unable to change its zpool parameter back to zsmalloc, if it has any existing old zpool using zsmalloc with page(s) in it. Attempts to change the parameters will result in failure to create the zpool. This changes zswap to provide a unique name for each zpool creation.

---
 mm/zswap.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

@@ -170,6 +170,8 @@ static struct zswap_tree *zswap_trees[MA
 static LIST_HEAD(zswap_pools);
 /* protects zswap_pools list modification */
 static DEFINE_SPINLOCK(zswap_pools_lock);
+/* pool counter to provide unique names to zpool */
+static atomic_t zswap_pools_count = ATOMIC_INIT(0);
 
 /* used by param callback function */
 static bool zswap_init_started;

@@ -565,6 +567,7 @@ static struct zswap_pool *zswap_pool_fin
 static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
 {
 	struct zswap_pool *pool;
+	char name[38]; /* 'zswap' + 32 char (max) num + \0 */
 	gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
 
 	pool = kzalloc(sizeof(*pool), GFP_KERNEL);

@@ -573,7 +576,10 @@ static struct zswap_pool *zswap_pool_cre
 		return NULL;
 	}
 
-	pool->zpool = zpool_create_pool(type, "zswap", gfp, &zswap_zpool_ops);
+	/* unique name for each pool specifically required by zsmalloc */
+	snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
+
+	pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
 	if (!pool->zpool) {
 		pr_err("%s zpool not available\n", type);
 		goto error;

Patches currently in stable-queue which might be from [email protected] are

queue-4.5/mm-zswap-provide-unique-zpool-name.patch