mm: zswap: refactor limit checking from zswap_store()

Refactor limit and acceptance threshold checking outside of zswap_store().
This code will be moved around in a following patch, so it would be
cleaner to move a function call around.

Link: https://lkml.kernel.org/r/20240413022407.785696-3-yosryahmed@google.comSigned-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/zswap.c

@@ -517,6 +517,21 @@ unsigned long zswap_total_pages(void)
 	return total;
 }
 
+static bool zswap_check_limits(void)
+{
+	unsigned long cur_pages = zswap_total_pages();
+	unsigned long max_pages = zswap_max_pages();
+
+	if (cur_pages >= max_pages) {
+		zswap_pool_limit_hit++;
+		zswap_pool_reached_full = true;
+	} else if (zswap_pool_reached_full &&
+		   cur_pages <= zswap_accept_thr_pages()) {
+			zswap_pool_reached_full = false;
+	}
+	return zswap_pool_reached_full;
+}
+
 /*********************************
 * param callbacks
 **********************************/
@@ -1406,7 +1421,6 @@ bool zswap_store(struct folio *folio)
 	struct zswap_entry *entry, *old;
 	struct obj_cgroup *objcg = NULL;
 	struct mem_cgroup *memcg = NULL;
-	unsigned long max_pages, cur_pages;
 
 	VM_WARN_ON_ONCE(!folio_test_locked(folio));
 	VM_WARN_ON_ONCE(!folio_test_swapcache(folio));
@@ -1429,22 +1443,8 @@ bool zswap_store(struct folio *folio)
 		mem_cgroup_put(memcg);
 	}
 
-	/* Check global limits */
-	cur_pages = zswap_total_pages();
-	max_pages = zswap_max_pages();
-
-	if (cur_pages >= max_pages) {
-		zswap_pool_limit_hit++;
-		zswap_pool_reached_full = true;
+	if (zswap_check_limits())
 		goto reject;
-	}
-
-	if (zswap_pool_reached_full) {
-		if (cur_pages > zswap_accept_thr_pages())
-			goto reject;
-		else
-			zswap_pool_reached_full = false;
-	}
 
 	/* allocate entry */
 	entry = zswap_entry_cache_alloc(GFP_KERNEL, folio_nid(folio));