Commit 274519ed authored by Gregory Price's avatar Gregory Price Committed by Andrew Morton
Browse files

mm/mempolicy: protect task interleave functions with tsk->mems_allowed_seq 

In the event of rebind, pol->nodemask can change at the same time as an
allocation occurs.  We can detect this with tsk->mems_allowed_seq and
prevent a miscount or an allocation failure from occurring.

The same thing happens in the allocators to detect failure, but this can
prevent spurious failures in a much smaller critical section.

[gourry.memverge@gmail.com: weighted interleave checks wrong parameter]
  Link: https://lkml.kernel.org/r/20240206192853.3589-1-gregory.price@memverge.com
Link: https://lkml.kernel.org/r/20240202170238.90004-5-gregory.price@memverge.com


Signed-off-by: default avatarGregory Price <gregory.price@memverge.com>
Suggested-by: default avatar"Huang, Ying" <ying.huang@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Hasan Al Maruf <Hasan.Maruf@amd.com>
Cc: Honggyu Kim <honggyu.kim@sk.com>
Cc: Hyeongtak Ji <hyeongtak.ji@sk.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Ravi Jonnalagadda <ravis.opensrc@micron.com>
Cc: Srinivasulu Thanneeru <sthanneeru.opensrc@micron.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent fa3bea4e

mm/mempolicy.c

+23 −4
Original line number Diff line number Diff line
@@ -1874,11 +1874,17 @@ bool apply_policy_zone(struct mempolicy *policy, enum zone_type zone) 


static unsigned int weighted_interleave_nodes(struct mempolicy *policy)

{

	unsigned int node = current->il_prev;

	unsigned int node;

	unsigned int cpuset_mems_cookie;



retry:

	/* to prevent miscount use tsk->mems_allowed_seq to detect rebind */

	cpuset_mems_cookie = read_mems_allowed_begin();

	node = current->il_prev;

	if (!current->il_weight || !node_isset(node, policy->nodes)) {

		node = next_node_in(node, policy->nodes);

		/* can only happen if nodemask is being rebound */

		if (read_mems_allowed_retry(cpuset_mems_cookie))

			goto retry;

		if (node == MAX_NUMNODES)

			return node;

		current->il_prev = node;
@@ -1892,8 +1898,14 @@ static unsigned int weighted_interleave_nodes(struct mempolicy *policy) 
static unsigned int interleave_nodes(struct mempolicy *policy)

{

	unsigned int nid;

	unsigned int cpuset_mems_cookie;



	/* to prevent miscount, use tsk->mems_allowed_seq to detect rebind */

	do {

		cpuset_mems_cookie = read_mems_allowed_begin();

		nid = next_node_in(current->il_prev, policy->nodes);

	} while (read_mems_allowed_retry(cpuset_mems_cookie));



	if (nid < MAX_NUMNODES)

		current->il_prev = nid;

	return nid;
@@ -2370,6 +2382,7 @@ static unsigned long alloc_pages_bulk_array_weighted_interleave(gfp_t gfp, 
		struct page **page_array)

{

	struct task_struct *me = current;

	unsigned int cpuset_mems_cookie;

	unsigned long total_allocated = 0;

	unsigned long nr_allocated = 0;

	unsigned long rounds;
@@ -2387,7 +2400,13 @@ static unsigned long alloc_pages_bulk_array_weighted_interleave(gfp_t gfp, 
	if (!nr_pages)

		return 0;



	/* read the nodes onto the stack, retry if done during rebind */

	do {

		cpuset_mems_cookie = read_mems_allowed_begin();

		nnodes = read_once_policy_nodemask(pol, &nodes);

	} while (read_mems_allowed_retry(cpuset_mems_cookie));



	/* if the nodemask has become invalid, we cannot do anything */

	if (!nnodes)

		return 0;