mm: zswap: rename zswap_pool_get() to zswap_pool_tryget()

Modify the name of the existing zswap_pool_get() to zswap_pool_tryget() to
be representative of the call it makes to percpu_ref_tryget().  A
subsequent patch will introduce a new zswap_pool_get() that calls
percpu_ref_get().

The intent behind this change is for higher level zswap API such as
zswap_store() to call zswap_pool_tryget() to check upfront if the pool's
refcount is "0" (which means it could be getting destroyed) and to handle
this as an error condition.  zswap_store() would proceed only if
zswap_pool_tryget() returns success, and any additional pool refcounts
that need to be obtained for compressing sub-pages in a large folio could
simply call zswap_pool_get().

Link: https://lkml.kernel.org/r/20241001053222.6944-4-kanchana.p.sridhar@intel.com
Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Wajdi Feghali <wajdi.k.feghali@intel.com>
Cc: "Zou, Nanhai" <nanhai.zou@intel.com>
Cc: Barry Song <21cnbao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: kparasur

mm/zswap.c

@@ -402,7 +402,7 @@ static void __zswap_pool_empty(struct percpu_ref *ref)
 	spin_unlock_bh(&zswap_pools_lock);
 }
 
-static int __must_check zswap_pool_get(struct zswap_pool *pool)
+static int __must_check zswap_pool_tryget(struct zswap_pool *pool)
 {
 	if (!pool)
 		return 0;
@@ -440,7 +440,7 @@ static struct zswap_pool *zswap_pool_current_get(void)
 	rcu_read_lock();
 
 	pool = __zswap_pool_current();
-	if (!zswap_pool_get(pool))
+	if (!zswap_pool_tryget(pool))
 		pool = NULL;
 
 	rcu_read_unlock();
@@ -461,7 +461,7 @@ static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
 		if (strcmp(zpool_get_type(pool->zpool), type))
 			continue;
 		/* if we can't get it, it's about to be destroyed */
-		if (!zswap_pool_get(pool))
+		if (!zswap_pool_tryget(pool))
 			continue;
 		return pool;
 	}