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.

Dan Streetman committed 10 years ago

Commit 32a4e161 parent 127393f1 file · +7 −1Browse files

Unified · Split

mm/zswap.c+7−1

@@ -170,6 +170,8 @@ static struct zswap_tree *zswap_trees[MAX_SWAPFILES]; · 169 unmodified lines
170	170	static LIST_HEAD(zswap_pools);
171	171	/* protects zswap_pools list modification */
172	172	static DEFINE_SPINLOCK(zswap_pools_lock);
	173	+/* pool counter to provide unique names to zpool */
	174	+static atomic_t zswap_pools_count = ATOMIC_INIT(0);
173	175
174	176	/* used by param callback function */
175	177	static bool zswap_init_started;
@@ -565,6 +567,7 @@ static struct zswap_pool zswap_pool_find_get(char type, char *compressor) · 389 unmodified lines
565	567	static struct zswap_pool zswap_pool_create(char type, char *compressor)
566	568	{
567	569	struct zswap_pool *pool;
	570	+ char name[38]; /* 'zswap' + 32 char (max) num + \0 */
568	571	gfp_t gfp = __GFP_NORETRY \| __GFP_NOWARN \| __GFP_KSWAPD_RECLAIM;
569	572
570	573	pool = kzalloc(sizeof(*pool), GFP_KERNEL);
@@ -573,7 +576,10 @@ static struct zswap_pool zswap_pool_create(char type, char *compressor) · 2 unmodified lines
573	576	return NULL;
574	577	}
575	578
576		− pool->zpool = zpool_create_pool(type, "zswap", gfp, &zswap_zpool_ops);
	579	+ /* unique name for each pool specifically required by zsmalloc */
	580	+ snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
	581	+
	582	+ pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
577	583	if (!pool->zpool) {
578	584	pr_err("%s zpool not available\n", type);
579	585	goto error;