The patch titled
Subject: mm/mempolicy: protect task interleave functions with tsk->mems_allowed_seq
has been added to the -mm mm-unstable branch. Its filename is
mm-mempolicy-protect-task-interleave-functions-with-tsk-mems_allowed_seq.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mempolicy-protect-task-interleave-functions-with-tsk-mems_allowed_seq.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Gregory Price <gourry.memverge@xxxxxxxxx>
Subject: mm/mempolicy: protect task interleave functions with tsk->mems_allowed_seq
Date: Fri, 2 Feb 2024 12:02:38 -0500
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.
Link: https://lkml.kernel.org/r/20240202170238.90004-5-gregory.price@xxxxxxxxxxxx
Signed-off-by: Gregory Price <gregory.price@xxxxxxxxxxxx>
Suggested-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Hasan Al Maruf <Hasan.Maruf@xxxxxxx>
Cc: Honggyu Kim <honggyu.kim@xxxxxx>
Cc: Hyeongtak Ji <hyeongtak.ji@xxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Rakie Kim <rakie.kim@xxxxxx>
Cc: Ravi Jonnalagadda <ravis.opensrc@xxxxxxxxxx>
Cc: Srinivasulu Thanneeru <sthanneeru.opensrc@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mempolicy.c | 29 ++++++++++++++++++++++++-----
1 file changed, 24 insertions(+), 5 deletions(-)
--- a/mm/mempolicy.c~mm-mempolicy-protect-task-interleave-functions-with-tsk-mems_allowed_seq
+++ a/mm/mempolicy.c
@@ -1874,11 +1874,17 @@ bool apply_policy_zone(struct mempolicy
static unsigned int weighted_interleave_nodes(struct mempolicy *policy)
{
- unsigned int node = current->il_prev;
+ unsigned int node;
+ unsigned int cpuset_mems_cookie;
- if (!current->il_weight || !node_isset(node, policy->nodes)) {
+retry:
+ /* to prevent miscount use tsk->mems_allowed_seq to detect rebind */
+ cpuset_mems_cookie = read_mems_allowed_begin();
+ node = current->il_prev;
+ if (!node || !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_
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));
- nid = next_node_in(current->il_prev, policy->nodes);
if (nid < MAX_NUMNODES)
current->il_prev = nid;
return nid;
@@ -2370,6 +2382,7 @@ static unsigned long alloc_pages_bulk_ar
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_ar
if (!nr_pages)
return 0;
- nnodes = read_once_policy_nodemask(pol, &nodes);
+ /* 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;
_
Patches currently in -mm which might be from gourry.memverge@xxxxxxxxx are
mm-mempolicy-refactor-a-read-once-mechanism-into-a-function-for-re-use.patch
mm-mempolicy-introduce-mpol_weighted_interleave-for-weighted-interleaving.patch
mm-mempolicy-protect-task-interleave-functions-with-tsk-mems_allowed_seq.patch
