lkml.org 
[lkml]   [2015]   [Sep]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 1/2] mm/slab_common: add SLAB_NO_MERGE flag for use when creating slabs
Date
The slab aliasing/merging by default transition went unnoticed (at least
to the DM subsystem). Add a new SLAB_NO_MERGE flag that allows
individual slabs to be created without slab merging. This beats forcing
all slabs to be created in this fashion by specifying sl[au]b_nomerge on
the kernel commandline.

DM has historically taken care to have separate named slabs that each
devices' mempool_t are backed by. These separate slabs are useful --
even if only to aid inspection of DM's memory use (via /proc/slabinfo)
on production systems.

I stumbled onto slab merging as a side-effect of a leak in dm-cache
being attributed to 'kmalloc-96' rather than the expected
'dm_bio_prison_cell' named slab. Moving forward DM will disable slab
merging for all of DM's slabs by using SLAB_NO_MERGE.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
include/linux/slab.h | 2 ++
mm/slab.h | 2 +-
mm/slab_common.c | 2 +-
3 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index a99f0e5..d007407 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -87,6 +87,8 @@
# define SLAB_FAILSLAB 0x00000000UL
#endif

+#define SLAB_NO_MERGE 0x04000000UL /* Do not merge with existing slab */
+
/* The following flags affect the page allocator grouping pages by mobility */
#define SLAB_RECLAIM_ACCOUNT 0x00020000UL /* Objects are reclaimable */
#define SLAB_TEMPORARY SLAB_RECLAIM_ACCOUNT /* Objects are short-lived */
diff --git a/mm/slab.h b/mm/slab.h
index 8da63e4..35eb6f4 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -115,7 +115,7 @@ static inline unsigned long kmem_cache_flags(unsigned long object_size,

/* Legal flag mask for kmem_cache_create(), for various configurations */
#define SLAB_CORE_FLAGS (SLAB_HWCACHE_ALIGN | SLAB_CACHE_DMA | SLAB_PANIC | \
- SLAB_DESTROY_BY_RCU | SLAB_DEBUG_OBJECTS )
+ SLAB_DESTROY_BY_RCU | SLAB_DEBUG_OBJECTS | SLAB_NO_MERGE)

#if defined(CONFIG_DEBUG_SLAB)
#define SLAB_DEBUG_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 8683110..3a5a8ed 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -35,7 +35,7 @@ struct kmem_cache *kmem_cache;
*/
#define SLAB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
SLAB_TRACE | SLAB_DESTROY_BY_RCU | SLAB_NOLEAKTRACE | \
- SLAB_FAILSLAB)
+ SLAB_FAILSLAB | SLAB_NO_MERGE)

#define SLAB_MERGE_SAME (SLAB_RECLAIM_ACCOUNT | SLAB_CACHE_DMA | SLAB_NOTRACK)

--
2.3.2 (Apple Git-55)


\
 
 \ /
  Last update: 2015-09-01 20:01    [W:0.032 / U:2.148 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site