gfp: add __GFP_NOACCOUNT

Not all kmem allocations should be accounted to memcg.  The following
patch gives an example when accounting of a certain type of allocations to
memcg can effectively result in a memory leak.  This patch adds the
__GFP_NOACCOUNT flag which if passed to kmalloc and friends will force the
allocation to go through the root cgroup.  It will be used by the next
patch.

Note, since in case of kmemleak enabled each kmalloc implies yet another
allocation from the kmemleak_object cache, we add __GFP_NOACCOUNT to
gfp_kmemleak_mask.

Alternatively, we could introduce a per kmem cache flag disabling
accounting for all allocations of a particular kind, but (a) we would not
be able to bypass accounting for kmalloc then and (b) a kmem cache with
this flag set could not be merged with a kmem cache without this flag,
which would increase the number of global caches and therefore
fragmentation even if the memory cgroup controller is not used.

Despite its generic name, currently __GFP_NOACCOUNT disables accounting
only for kmem allocations while user page allocations are always charged.
To catch abusing of this flag, a warning is issued on an attempt of
passing it to mem_cgroup_try_charge.

Signed-off-by: Vladimir Davydov <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Greg Thelen <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: <[email protected]>	[4.0.x]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 97a9373e61e80d048ee6259eb4962bd831cac822..15928f0647e44187eb00ae7e128f4047519b093b 100644 (file)
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -30,6 +30,7 @@ struct vm_area_struct;
 #define ___GFP_HARDWALL                0x20000u
 #define ___GFP_THISNODE                0x40000u
 #define ___GFP_RECLAIMABLE     0x80000u
+#define ___GFP_NOACCOUNT       0x100000u
 #define ___GFP_NOTRACK         0x200000u
 #define ___GFP_NO_KSWAPD       0x400000u
 #define ___GFP_OTHER_NODE      0x800000u
@@ -87,6 +88,7 @@ struct vm_area_struct;
 #define __GFP_HARDWALL   ((__force gfp_t)___GFP_HARDWALL) /* Enforce hardwall cpuset memory allocs */
 #define __GFP_THISNODE ((__force gfp_t)___GFP_THISNODE)/* No fallback, no policies */
 #define __GFP_RECLAIMABLE ((__force gfp_t)___GFP_RECLAIMABLE) /* Page is reclaimable */
+#define __GFP_NOACCOUNT        ((__force gfp_t)___GFP_NOACCOUNT) /* Don't account to kmemcg */
 #define __GFP_NOTRACK  ((__force gfp_t)___GFP_NOTRACK)  /* Don't track with kmemcheck */
 
 #define __GFP_NO_KSWAPD        ((__force gfp_t)___GFP_NO_KSWAPD)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 72dff5fb0d0ceaf0386d80f1cba83c7bb2c7632f..6c8918114804fda89d00ed3e6b1482539f2dd4ee 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -463,6 +463,8 @@ memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup **memcg, int order)
        if (!memcg_kmem_enabled())
                return true;
 
+       if (gfp & __GFP_NOACCOUNT)
+               return true;
        /*
         * __GFP_NOFAIL allocations will move on even if charging is not
         * possible. Therefore we don't even try, and have this allocation
@@ -522,6 +524,8 @@ memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp)
 {
        if (!memcg_kmem_enabled())
                return cachep;
+       if (gfp & __GFP_NOACCOUNT)
+               return cachep;
        if (gfp & __GFP_NOFAIL)
                return cachep;
        if (in_interrupt() || (!current->mm) || (current->flags & PF_KTHREAD))

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 5405aff5a590c370d3c8ca37c0f9a0c19cb46775..f0fe4f2c1fa7aa865055731834cdd78e0684cca5 100644 (file)
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -115,7 +115,8 @@
 #define BYTES_PER_POINTER      sizeof(void *)
 
 /* GFP bitmask for kmemleak internal allocations */
-#define gfp_kmemleak_mask(gfp) (((gfp) & (GFP_KERNEL | GFP_ATOMIC)) | \
+#define gfp_kmemleak_mask(gfp) (((gfp) & (GFP_KERNEL | GFP_ATOMIC | \
+                                          __GFP_NOACCOUNT)) | \
                                 __GFP_NORETRY | __GFP_NOMEMALLOC | \
                                 __GFP_NOWARN)