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[PATCH review for 4.9 24/50] slub: do not merge cache if slub_debug contains a never-merge flag

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From: Grygorii Maistrenko <grygoriimkd@gmail.com>

[ Upstream commit c6e28895a4372992961888ffaadc9efc643b5bfe ]

In case CONFIG_SLUB_DEBUG_ON=n, find_mergeable() gets debug features from
commandline but never checks if there are features from the
SLAB_NEVER_MERGE set.

As a result selected by slub_debug caches are always mergeable if they
have been created without a custom constructor set or without one of the
SLAB_* debug features on.

This moves the SLAB_NEVER_MERGE check below the flags update from
commandline to make sure it won't merge the slab cache if one of the debug
features is on.

Link: http://lkml.kernel.org/r/20170101124451.GA4740@lp-laptop-d
Signed-off-by: Grygorii Maistrenko <grygoriimkd@gmail.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
---
 mm/slab_common.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 5d2f24fbafc5..622f6b6ae844 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -255,7 +255,7 @@ struct kmem_cache *find_mergeable(size_t size, size_t align,
 {
 	struct kmem_cache *s;
 
-	if (slab_nomerge || (flags & SLAB_NEVER_MERGE))
+	if (slab_nomerge)
 		return NULL;
 
 	if (ctor)
@@ -266,6 +266,9 @@ struct kmem_cache *find_mergeable(size_t size, size_t align,
 	size = ALIGN(size, align);
 	flags = kmem_cache_flags(size, flags, name, NULL);
 
+	if (flags & SLAB_NEVER_MERGE)
+		return NULL;
+
 	list_for_each_entry_reverse(s, &slab_caches, list) {
 		if (slab_unmergeable(s))
 			continue;
-- 
2.11.0

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[PATCH review for 4.9 01/50] xen-netback: Use GFP_ATOMIC to allocate  hash "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-25 03:40 +0200
  [PATCH review for 4.9 17/50] f2fs: do not wait for writeback in  write_begin "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-25 03:40 +0200
  [PATCH review for 4.9 15/50] sched/fair: Update rq clock before  changing a task's CPU affinity "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-25 03:40 +0200
  [PATCH review for 4.9 26/50] ASoC: mediatek: add I2C dependency for  CS42XX8 "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-25 03:40 +0200
  [PATCH review for 4.9 42/50] hrtimer: Catch invalid clockids again "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-25 03:40 +0200
  [PATCH review for 4.9 06/50] mac80211_hwsim: check  HWSIM_ATTR_RADIO_NAME length "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-25 03:40 +0200
  [PATCH review for 4.9 07/50] ALSA: hda: Add Geminilake HDMI codec ID "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-25 03:40 +0200
  [PATCH review for 4.9 05/50] initramfs: finish fput() before  accessing any binary from initramfs "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-25 03:40 +0200
  [PATCH review for 4.9 14/50] f2fs: do SSR for data when there is  enough free space "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-25 03:40 +0200
  [PATCH review for 4.9 02/50] locking/lockdep: Add nest_lock integrity  test "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-25 03:40 +0200
  [PATCH review for 4.9 18/50] md/linear: shutup lockdep warnning "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-25 03:40 +0200
  [PATCH review for 4.9 12/50] netfilter: nf_ct_expect: Change  __nf_ct_expect_check() return value. "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-25 03:40 +0200
  [PATCH review for 4.9 24/50] slub: do not merge cache if slub_debug  contains a never-merge flag "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-25 03:40 +0200

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