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authorFeng Tang <feng.tang@intel.com>2022-08-05 08:59:03 +0800
committerAndrew Morton <akpm@linux-foundation.org>2022-09-11 20:25:50 -0700
commitd2226ebd5484afcf9f9b71b394ec1567a7730eb1 (patch)
tree71e1c4476f6a3dd7a4932e694799e162de32517b /mm/hugetlb.c
parent12c1dc8e7441773c74dc62fab76553c24015f6e1 (diff)
mm/hugetlb: add dedicated func to get 'allowed' nodemask for current process
Muchun Song found that after MPOL_PREFERRED_MANY policy was introduced in commit b27abaccf8e8 ("mm/mempolicy: add MPOL_PREFERRED_MANY for multiple preferred nodes"), the policy_nodemask_current()'s semantics for this new policy has been changed, which returns 'preferred' nodes instead of 'allowed' nodes. With the changed semantic of policy_nodemask_current, a task with MPOL_PREFERRED_MANY policy could fail to get its reservation even though it can fall back to other nodes (either defined by cpusets or all online nodes) for that reservation failing mmap calles unnecessarily early. The fix is to not consider MPOL_PREFERRED_MANY for reservations at all because they, unlike MPOL_MBIND, do not pose any actual hard constrain. Michal suggested the policy_nodemask_current() is only used by hugetlb, and could be moved to hugetlb code with more explicit name to enforce the 'allowed' semantics for which only MPOL_BIND policy matters. apply_policy_zone() is made extern to be called in hugetlb code and its return value is changed to bool. [1]. https://lore.kernel.org/lkml/20220801084207.39086-1-songmuchun@bytedance.com/t/ Link: https://lkml.kernel.org/r/20220805005903.95563-1-feng.tang@intel.com Fixes: b27abaccf8e8 ("mm/mempolicy: add MPOL_PREFERRED_MANY for multiple preferred nodes") Signed-off-by: Feng Tang <feng.tang@intel.com> Reported-by: Muchun Song <songmuchun@bytedance.com> Suggested-by: Michal Hocko <mhocko@suse.com> Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Muchun Song <songmuchun@bytedance.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Ben Widawsky <bwidawsk@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/hugetlb.c')
-rw-r--r--mm/hugetlb.c24
1 files changed, 20 insertions, 4 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e070b8593b37..ea1c7bfa1cc3 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4330,18 +4330,34 @@ static int __init default_hugepagesz_setup(char *s)
}
__setup("default_hugepagesz=", default_hugepagesz_setup);
+static nodemask_t *policy_mbind_nodemask(gfp_t gfp)
+{
+#ifdef CONFIG_NUMA
+ struct mempolicy *mpol = get_task_policy(current);
+
+ /*
+ * Only enforce MPOL_BIND policy which overlaps with cpuset policy
+ * (from policy_nodemask) specifically for hugetlb case
+ */
+ if (mpol->mode == MPOL_BIND &&
+ (apply_policy_zone(mpol, gfp_zone(gfp)) &&
+ cpuset_nodemask_valid_mems_allowed(&mpol->nodes)))
+ return &mpol->nodes;
+#endif
+ return NULL;
+}
+
static unsigned int allowed_mems_nr(struct hstate *h)
{
int node;
unsigned int nr = 0;
- nodemask_t *mpol_allowed;
+ nodemask_t *mbind_nodemask;
unsigned int *array = h->free_huge_pages_node;
gfp_t gfp_mask = htlb_alloc_mask(h);
- mpol_allowed = policy_nodemask_current(gfp_mask);
-
+ mbind_nodemask = policy_mbind_nodemask(gfp_mask);
for_each_node_mask(node, cpuset_current_mems_allowed) {
- if (!mpol_allowed || node_isset(node, *mpol_allowed))
+ if (!mbind_nodemask || node_isset(node, *mbind_nodemask))
nr += array[node];
}