Commit e7b691b0 authored by Andi Kleen's avatar Andi Kleen Committed by Pekka Enberg
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slab/mempolicy: always use local policy from interrupt context 



slab_node() could access current->mempolicy from interrupt context.
However there's a race condition during exit where the mempolicy
is first freed and then the pointer zeroed.

Using this from interrupts seems bogus anyways. The interrupt
will interrupt a random process and therefore get a random
mempolicy. Many times, this will be idle's, which noone can change.

Just disable this here and always use local for slab
from interrupts. I also cleaned up the callers of slab_node a bit
which always passed the same argument.

I believe the original mempolicy code did that in fact,
so it's likely a regression.

v2: send version with correct logic
v3: simplify. fix typo.
Reported-by: default avatarArun Sharma <asharma@fb.com>
Cc: penberg@kernel.org
Cc: cl@linux.com
Signed-off-by: default avatarAndi Kleen <ak@linux.intel.com>
[tdmackey@twitter.com: Rework control flow based on feedback from
cl@linux.com, fix logic, and cleanup current task_struct reference]
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Acked-by: default avatarChristoph Lameter <cl@linux.com>
Acked-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarDavid Mackey <tdmackey@twitter.com>
Signed-off-by: default avatarPekka Enberg <penberg@kernel.org>
parent 8c138bc0

include/linux/mempolicy.h

+1 −1
Original line number Diff line number Diff line
@@ -215,7 +215,7 @@ extern struct zonelist *huge_zonelist(struct vm_area_struct *vma, 
extern bool init_nodemask_of_mempolicy(nodemask_t *mask);

extern bool mempolicy_nodemask_intersects(struct task_struct *tsk,

				const nodemask_t *mask);

extern unsigned slab_node(struct mempolicy *policy);

extern unsigned slab_node(void);



extern enum zone_type policy_zone;

mm/mempolicy.c

+7 −1
Original line number Diff line number Diff line
@@ -1602,8 +1602,14 @@ static unsigned interleave_nodes(struct mempolicy *policy) 
 * task can change it's policy.  The system default policy requires no

 * such protection.

 */

unsigned slab_node(struct mempolicy *policy)

unsigned slab_node(void)

{

	struct mempolicy *policy;



	if (in_interrupt())

		return numa_node_id();



	policy = current->mempolicy;

	if (!policy || policy->flags & MPOL_F_LOCAL)

		return numa_node_id();

mm/slab.c

+2 −2
Original line number Diff line number Diff line
@@ -3310,7 +3310,7 @@ static void *alternate_node_alloc(struct kmem_cache *cachep, gfp_t flags) 
	if (cpuset_do_slab_mem_spread() && (cachep->flags & SLAB_MEM_SPREAD))

		nid_alloc = cpuset_slab_spread_node();

	else if (current->mempolicy)

		nid_alloc = slab_node(current->mempolicy);

		nid_alloc = slab_node();

	if (nid_alloc != nid_here)

		return ____cache_alloc_node(cachep, flags, nid_alloc);

	return NULL;
@@ -3342,7 +3342,7 @@ static void *fallback_alloc(struct kmem_cache *cache, gfp_t flags) 


retry_cpuset:

	cpuset_mems_cookie = get_mems_allowed();

	zonelist = node_zonelist(slab_node(current->mempolicy), flags);

	zonelist = node_zonelist(slab_node(), flags);



retry:

	/*

mm/slub.c

+1 −1
Original line number Diff line number Diff line
@@ -1617,7 +1617,7 @@ static void *get_any_partial(struct kmem_cache *s, gfp_t flags, 


	do {

		cpuset_mems_cookie = get_mems_allowed();

		zonelist = node_zonelist(slab_node(current->mempolicy), flags);

		zonelist = node_zonelist(slab_node(), flags);

		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {

			struct kmem_cache_node *n;

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