[PATCH 2/2] mm/slub: disable merging after enabling debug in runtime

[Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>]

Enabling debug in runtime breaks creation of new kmem caches:
they have incompatible flags thus cannot be merged but unique
names are taken by existing caches.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
---
 mm/slab.h        |    2 ++
 mm/slab_common.c |    2 +-
 mm/slub.c        |    9 ++++++++-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/mm/slab.h b/mm/slab.h
index 8da63e4e470f..c8998f1d270f 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -66,6 +66,8 @@ extern struct list_head slab_caches;
 /* The slab cache that manages slab cache information */
 extern struct kmem_cache *kmem_cache;
 
+extern int slab_nomerge;
+
 unsigned long calculate_alignment(unsigned long flags,
 		unsigned long align, unsigned long size);
 
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 3e5f8f29c286..eae96f0e7f29 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -44,7 +44,7 @@ struct kmem_cache *kmem_cache;
  * Merge control. If this is set then no merging of slab caches will occur.
  * (Could be removed. This was introduced to pacify the merge skeptics.)
  */
-static int slab_nomerge;
+int slab_nomerge __read_mostly;
 
 static int __init setup_slab_nomerge(char *str)
 {
diff --git a/mm/slub.c b/mm/slub.c
index 4497cae6a914..94300ced4c96 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4610,6 +4610,7 @@ static ssize_t sanity_checks_store(struct kmem_cache *s,
 	if (buf[0] == '1') {
 		s->flags &= ~__CMPXCHG_DOUBLE;
 		s->flags |= SLAB_DEBUG_FREE;
+		slab_nomerge = 1;
 	}
 	return length;
 }
@@ -4635,6 +4636,7 @@ static ssize_t trace_store(struct kmem_cache *s, const char *buf,
 	if (buf[0] == '1') {
 		s->flags &= ~__CMPXCHG_DOUBLE;
 		s->flags |= SLAB_TRACE;
+		slab_nomerge = 1;
 	}
 	return length;
 }
@@ -4655,6 +4657,7 @@ static ssize_t red_zone_store(struct kmem_cache *s,
 	if (buf[0] == '1') {
 		s->flags &= ~__CMPXCHG_DOUBLE;
 		s->flags |= SLAB_RED_ZONE;
+		slab_nomerge = 1;
 	}
 	calculate_sizes(s, -1);
 	return length;
@@ -4676,6 +4679,7 @@ static ssize_t poison_store(struct kmem_cache *s,
 	if (buf[0] == '1') {
 		s->flags &= ~__CMPXCHG_DOUBLE;
 		s->flags |= SLAB_POISON;
+		slab_nomerge = 1;
 	}
 	calculate_sizes(s, -1);
 	return length;
@@ -4697,6 +4701,7 @@ static ssize_t store_user_store(struct kmem_cache *s,
 	if (buf[0] == '1') {
 		s->flags &= ~__CMPXCHG_DOUBLE;
 		s->flags |= SLAB_STORE_USER;
+		slab_nomerge = 1;
 	}
 	calculate_sizes(s, -1);
 	return length;
@@ -4752,8 +4757,10 @@ static ssize_t failslab_store(struct kmem_cache *s, const char *buf,
 		return -EINVAL;
 
 	s->flags &= ~SLAB_FAILSLAB;
-	if (buf[0] == '1')
+	if (buf[0] == '1') {
 		s->flags |= SLAB_FAILSLAB;
+		slab_nomerge = 1;
+	}
 	return length;
 }
 SLAB_ATTR(failslab);

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