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Date: Mon, 25 Mar 2024 23:50:12 +0000
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Subject: [RFC PATCH 4/9] mm: zswap: move more same-filled pages checks outside
 of zswap_store()
From: Yosry Ahmed <yosryahmed@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>, Nhat Pham <nphamcs@gmail.com>, 
	Chengming Zhou <chengming.zhou@linux.dev>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, 
	Yosry Ahmed <yosryahmed@google.com>
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Currently, zswap_store() check zswap_same_filled_pages_enabled, kmaps
the folio, then calls zswap_is_page_same_filled() to check the folio
contents. Move this logic into zswap_is_page_same_filled() as well (and
rename it to use 'folio' while we are at it).

This makes zswap_store() cleaner, and makes following changes to that
logic contained within the helper.

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
---
 mm/zswap.c | 45 ++++++++++++++++++++++++---------------------
 1 file changed, 24 insertions(+), 21 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 6b890c8590ef7..498a6c5839bef 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1385,26 +1385,36 @@ static void shrink_worker(struct work_struct *w)
 	} while (zswap_total_pages() > thr);
 }
 
-static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
+static bool zswap_is_folio_same_filled(struct folio *folio, unsigned long *value)
 {
 	unsigned long *page;
 	unsigned long val;
 	unsigned int pos, last_pos = PAGE_SIZE / sizeof(*page) - 1;
+	bool ret;
 
-	page = (unsigned long *)ptr;
+	if (!zswap_same_filled_pages_enabled)
+		return false;
+
+	page = kmap_local_folio(folio, 0);
 	val = page[0];
 
-	if (val != page[last_pos])
-		return 0;
+	if (val != page[last_pos]) {
+		ret = false;
+		goto out;
+	}
 
 	for (pos = 1; pos < last_pos; pos++) {
-		if (val != page[pos])
-			return 0;
+		if (val != page[pos]) {
+			ret = false;
+			goto out;
+		}
 	}
 
 	*value = val;
-
-	return 1;
+	ret = true;
+out:
+	kunmap_local(page);
+	return ret;
 }
 
 static void zswap_fill_page(void *ptr, unsigned long value)
@@ -1438,6 +1448,7 @@ bool zswap_store(struct folio *folio)
 	struct obj_cgroup *objcg = NULL;
 	struct mem_cgroup *memcg = NULL;
 	struct zswap_entry *entry;
+	unsigned long value;
 
 	VM_WARN_ON_ONCE(!folio_test_locked(folio));
 	VM_WARN_ON_ONCE(!folio_test_swapcache(folio));
@@ -1470,19 +1481,11 @@ bool zswap_store(struct folio *folio)
 		goto reject;
 	}
 
-	if (zswap_same_filled_pages_enabled) {
-		unsigned long value;
-		u8 *src;
-
-		src = kmap_local_folio(folio, 0);
-		if (zswap_is_page_same_filled(src, &value)) {
-			kunmap_local(src);
-			entry->length = 0;
-			entry->value = value;
-			atomic_inc(&zswap_same_filled_pages);
-			goto insert_entry;
-		}
-		kunmap_local(src);
+	if (zswap_is_folio_same_filled(folio, &value)) {
+		entry->length = 0;
+		entry->value = value;
+		atomic_inc(&zswap_same_filled_pages);
+		goto insert_entry;
 	}
 
 	if (!zswap_non_same_filled_pages_enabled)
-- 
2.44.0.396.g6e790dbe36-goog