linux-kernel - [PATCH v3 1/2] mm: clean up validate

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Message-Id: <20190914000743.182739-1-yuzhao@google.com>
Date:   Fri, 13 Sep 2019 18:07:42 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Yu Zhao <yuzhao@...gle.com>
Subject: [PATCH v3 1/2] mm: clean up validate_slab()

The function doesn't need to return any value, and the check can be
done in one pass.

There is a behavior change: before the patch, we stop at the first
invalid free object; after the patch, we stop at the first invalid
object, free or in use. This shouldn't matter because the original
behavior isn't intended anyway.

Signed-off-by: Yu Zhao <yuzhao@...gle.com>
---
 mm/slub.c | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 8834563cdb4b..445ef8b2aec0 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4384,31 +4384,26 @@ static int count_total(struct page *page)
 #endif
 
 #ifdef CONFIG_SLUB_DEBUG
-static int validate_slab(struct kmem_cache *s, struct page *page,
+static void validate_slab(struct kmem_cache *s, struct page *page,
 						unsigned long *map)
 {
 	void *p;
 	void *addr = page_address(page);
 
-	if (!check_slab(s, page) ||
-			!on_freelist(s, page, NULL))
-		return 0;
+	if (!check_slab(s, page) || !on_freelist(s, page, NULL))
+		return;
 
 	/* Now we know that a valid freelist exists */
 	bitmap_zero(map, page->objects);
 
 	get_map(s, page, map);
 	for_each_object(p, s, addr, page->objects) {
-		if (test_bit(slab_index(p, s, addr), map))
-			if (!check_object(s, page, p, SLUB_RED_INACTIVE))
-				return 0;
-	}
+		u8 val = test_bit(slab_index(p, s, addr), map) ?
+			 SLUB_RED_INACTIVE : SLUB_RED_ACTIVE;
 
-	for_each_object(p, s, addr, page->objects)
-		if (!test_bit(slab_index(p, s, addr), map))
-			if (!check_object(s, page, p, SLUB_RED_ACTIVE))
-				return 0;
-	return 1;
+		if (!check_object(s, page, p, val))
+			break;
+	}
 }
 
 static void validate_slab_slab(struct kmem_cache *s, struct page *page,
-- 
2.23.0.237.gc6a4ce50a0-goog