[merged] slub-relax-cmpxchg-consistency-restrictions.patch removed from -mm tree

[merged] slub-relax-cmpxchg-consistency-restrictions.patch removed from -mm tree

[akpm]

The patch titled
     Subject: slub: relax CMPXCHG consistency restrictions
has been removed from the -mm tree.  Its filename was
     slub-relax-cmpxchg-consistency-restrictions.patch

This patch was dropped because it was merged into mainline or a subsystem tree

------------------------------------------------------
From: Laura Abbott <labbott@fedoraproject.org>
Subject: slub: relax CMPXCHG consistency restrictions

When debug options are enabled, cmpxchg on the page is disabled.  This is
because the page must be locked to ensure there are no false positives
when performing consistency checks.  Some debug options such as poisoning
and red zoning only act on the object itself.  There is no need to protect
other CPUs from modification on only the object.  Allow cmpxchg to happen
with poisoning and red zoning are set on a slab.

Credit to Mathias Krause for the original work which inspired this series

Signed-off-by: Laura Abbott <labbott@fedoraproject.org>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/slub.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff -puN mm/slub.c~slub-relax-cmpxchg-consistency-restrictions mm/slub.c
--- a/mm/slub.c~slub-relax-cmpxchg-consistency-restrictions
+++ a/mm/slub.c
@@ -164,6 +164,14 @@ static inline bool kmem_cache_has_cpu_pa
 				SLAB_POISON | SLAB_STORE_USER)
 
 /*
+ * These debug flags cannot use CMPXCHG because there might be consistency
+ * issues when checking or reading debug information
+ */
+#define SLAB_NO_CMPXCHG (SLAB_CONSISTENCY_CHECKS | SLAB_STORE_USER | \
+				SLAB_TRACE)
+
+
+/*
  * Debugging flags that require metadata to be stored in the slab.  These get
  * disabled when slub_debug=O is used and a cache's min order increases with
  * metadata.
@@ -3338,7 +3346,7 @@ static int kmem_cache_open(struct kmem_c
 
 #if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
     defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
-	if (system_has_cmpxchg_double() && (s->flags & SLAB_DEBUG_FLAGS) == 0)
+	if (system_has_cmpxchg_double() && (s->flags & SLAB_NO_CMPXCHG) == 0)
 		/* Enable fast mode */
 		s->flags |= __CMPXCHG_DOUBLE;
 #endif
@@ -4846,7 +4854,6 @@ static ssize_t red_zone_store(struct kme
 
 	s->flags &= ~SLAB_RED_ZONE;
 	if (buf[0] == '1') {
-		s->flags &= ~__CMPXCHG_DOUBLE;
 		s->flags |= SLAB_RED_ZONE;
 	}
 	calculate_sizes(s, -1);
@@ -4867,7 +4874,6 @@ static ssize_t poison_store(struct kmem_
 
 	s->flags &= ~SLAB_POISON;
 	if (buf[0] == '1') {
-		s->flags &= ~__CMPXCHG_DOUBLE;
 		s->flags |= SLAB_POISON;
 	}
 	calculate_sizes(s, -1);
_

Patches currently in -mm which might be from labbott@fedoraproject.org are