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From: Yu Zhao <yuzhao@google.com>
To: Christoph Lameter <cl@linux.com>,
	Pekka Enberg <penberg@kernel.org>,
	 David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	 Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	 Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	 Yu Zhao <yuzhao@google.com>
Subject: [PATCH v2 1/4] mm: correct mask size for slub page->objects
Date: Wed, 11 Sep 2019 20:31:08 -0600
Message-ID: <20190912023111.219636-1-yuzhao@google.com> (raw)
In-Reply-To: <20190912004401.jdemtajrspetk3fh@box>

Mask of slub objects per page shouldn't be larger than what
page->objects can hold.

It requires more than 2^15 objects to hit the problem, and I don't
think anybody would. It'd be nice to have the mask fixed, but not
really worth cc'ing the stable.

Fixes: 50d5c41cd151 ("slub: Do not use frozen page flag but a bit in the page counters")
Signed-off-by: Yu Zhao <yuzhao@google.com>
---
 mm/slub.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index 8834563cdb4b..62053ceb4464 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -187,7 +187,7 @@ static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
  */
 #define DEBUG_METADATA_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)
 
-#define OO_SHIFT	16
+#define OO_SHIFT	15
 #define OO_MASK		((1 << OO_SHIFT) - 1)
 #define MAX_OBJS_PER_PAGE	32767 /* since page.objects is u15 */
 
@@ -343,6 +343,8 @@ static inline unsigned int oo_order(struct kmem_cache_order_objects x)
 
 static inline unsigned int oo_objects(struct kmem_cache_order_objects x)
 {
+	BUILD_BUG_ON(OO_MASK > MAX_OBJS_PER_PAGE);
+
 	return x.x & OO_MASK;
 }
 
-- 
2.23.0.162.g0b9fbb3734-goog



  parent reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-09  6:10 [PATCH] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-09 16:00 ` Kirill A. Shutemov
     [not found]   ` <e5e25aa3-651d-92b4-ac82-c5011c66a7cb@I-love.SAKURA.ne.jp>
2019-09-09 21:39     ` Yu Zhao
     [not found]       ` <201909100141.x8A1fVdu048305@www262.sakura.ne.jp>
2019-09-10  2:16         ` Yu Zhao
2019-09-10  9:16       ` Kirill A. Shutemov
2019-09-11 14:13 ` Andrew Morton
2019-09-12  0:29   ` [PATCH 1/3] mm: correct mask size for slub page->objects Yu Zhao
2019-09-12  0:29     ` [PATCH 2/3] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-12  0:44       ` Kirill A. Shutemov
2019-09-12  1:31         ` Yu Zhao
2019-09-12  2:31         ` Yu Zhao [this message]
2019-09-12  2:31           ` [PATCH v2 2/4] mm: clean up validate_slab() Yu Zhao
2019-09-12  9:46             ` Kirill A. Shutemov
2019-09-12  2:31           ` [PATCH v2 3/4] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-12 10:04             ` Kirill A. Shutemov
2019-09-12  2:31           ` [PATCH v2 4/4] mm: lock slub page when listing objects Yu Zhao
2019-09-12 10:06             ` Kirill A. Shutemov
2019-09-12 21:12               ` Yu Zhao
2019-09-13 14:58             ` Christopher Lameter
2019-09-12  9:40           ` [PATCH v2 1/4] mm: correct mask size for slub page->objects Kirill A. Shutemov
2019-09-12 21:11             ` Yu Zhao
2019-09-12 22:03               ` Kirill A. Shutemov
2019-09-14  0:07           ` [PATCH v3 1/2] mm: clean up validate_slab() Yu Zhao
2019-09-14  0:07             ` [PATCH v3 2/2] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-16  8:39             ` [PATCH v3 1/2] mm: clean up validate_slab() Kirill A. Shutemov
2019-11-08 19:39             ` [PATCH v4 " Yu Zhao
2019-11-08 19:39               ` [PATCH v4 2/2] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-11-09 20:52                 ` Christopher Lameter
2019-11-09 23:01                   ` Yu Zhao
2019-11-09 23:16                     ` Christopher Lameter
2019-11-10 18:47                       ` Yu Zhao
2019-11-11 15:47                         ` Christopher Lameter
2019-11-11 15:55                           ` [FIX] slub: Remove kmalloc under list_lock from list_slab_objects() V2 Christopher Lameter
2019-11-30 23:09                             ` Andrew Morton
2019-12-02 15:12                               ` Christopher Lameter
2019-12-07 22:03                                 ` Yu Zhao
2019-11-11 18:15                           ` [PATCH v4 2/2] mm: avoid slub allocation while holding list_lock Shakeel Butt
2019-09-12  0:29     ` [PATCH 3/3] mm: lock slub page when listing objects Yu Zhao

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