mm: zswap: modify zswap_stored_pages to be atomic_long_t

For zswap_store() to support large folios, we need to be able to do a
batch update of zswap_stored_pages upon successful store of all pages in
the folio.  For this, we need to add folio_nr_pages(), which returns a
long, to zswap_stored_pages.

Link: https://lkml.kernel.org/r/20241001053222.6944-6-kanchana.p.sridhar@intel.com
Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
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

fs/proc/meminfo.c

@@ -91,7 +91,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 #ifdef CONFIG_ZSWAP
 	show_val_kb(m, "Zswap:          ", zswap_total_pages());
 	seq_printf(m,  "Zswapped:       %8lu kB\n",
-		   (unsigned long)atomic_read(&zswap_stored_pages) <<
+		   (unsigned long)atomic_long_read(&zswap_stored_pages) <<
 		   (PAGE_SHIFT - 10));
 #endif
 	show_val_kb(m, "Dirty:          ",

include/linux/zswap.h

@@ -7,7 +7,7 @@
 
 struct lruvec;
 
-extern atomic_t zswap_stored_pages;
+extern atomic_long_t zswap_stored_pages;
 
 #ifdef CONFIG_ZSWAP
 

mm/zswap.c

@@ -43,7 +43,7 @@
 * statistics
 **********************************/
 /* The number of compressed pages currently stored in zswap */
-atomic_t zswap_stored_pages = ATOMIC_INIT(0);
+atomic_long_t zswap_stored_pages = ATOMIC_INIT(0);
 
 /*
  * The statistics below are not protected from concurrent access for
@@ -802,7 +802,7 @@ static void zswap_entry_free(struct zswap_entry *entry)
 		obj_cgroup_put(entry->objcg);
 	}
 	zswap_entry_cache_free(entry);
-	atomic_dec(&zswap_stored_pages);
+	atomic_long_dec(&zswap_stored_pages);
 }
 
 /*********************************
@@ -1233,7 +1233,7 @@ static unsigned long zswap_shrinker_count(struct shrinker *shrinker,
 		nr_stored = memcg_page_state(memcg, MEMCG_ZSWAPPED);
 	} else {
 		nr_backing = zswap_total_pages();
-		nr_stored = atomic_read(&zswap_stored_pages);
+		nr_stored = atomic_long_read(&zswap_stored_pages);
 	}
 
 	if (!nr_stored)
@@ -1502,7 +1502,7 @@ bool zswap_store(struct folio *folio)
 	}
 
 	/* update stats */
-	atomic_inc(&zswap_stored_pages);
+	atomic_long_inc(&zswap_stored_pages);
 	count_vm_event(ZSWPOUT);
 
 	return true;
@@ -1654,6 +1654,13 @@ static int debugfs_get_total_size(void *data, u64 *val)
 }
 DEFINE_DEBUGFS_ATTRIBUTE(total_size_fops, debugfs_get_total_size, NULL, "%llu\n");
 
+static int debugfs_get_stored_pages(void *data, u64 *val)
+{
+	*val = atomic_long_read(&zswap_stored_pages);
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(stored_pages_fops, debugfs_get_stored_pages, NULL, "%llu\n");
+
 static int zswap_debugfs_init(void)
 {
 	if (!debugfs_initialized())
@@ -1677,8 +1684,8 @@ static int zswap_debugfs_init(void)
 			   zswap_debugfs_root, &zswap_written_back_pages);
 	debugfs_create_file("pool_total_size", 0444,
 			    zswap_debugfs_root, NULL, &total_size_fops);
-	debugfs_create_atomic_t("stored_pages", 0444,
-				zswap_debugfs_root, &zswap_stored_pages);
+	debugfs_create_file("stored_pages", 0444,
+			    zswap_debugfs_root, NULL, &stored_pages_fops);
 
 	return 0;
 }