Commit 32a4e169 authored May 05, 2016 by Dan Streetman Committed by Linus Torvalds May 05, 2016

mm/zswap: provide unique zpool name



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.

Fixes: f1c54846 ("zswap: dynamic pool creation")
Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Dan Streetman <dan.streetman@canonical.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 127393fb

mm/zswap.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -170,6 +170,8 @@ static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
		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_find_get(char type, char *compressor)
		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_create(char type, char *compressor)
		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;

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