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Message-ID: <YuuC7MBQ1bX3jA0j@feng-clx>
Date: Thu, 4 Aug 2022 16:27:24 +0800
From: Feng Tang <feng.tang@...el.com>
To: Michal Hocko <mhocko@...e.com>,
Muchun Song <songmuchun@...edance.com>,
Mike Kravetz <mike.kravetz@...cle.com>,
Andrew Morton <akpm@...ux-foundation.org>
CC: "bwidawsk@...nel.org" <bwidawsk@...nel.org>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: mempolicy: fix policy_nodemask() for
MPOL_PREFERRED_MANY case
On Wed, Aug 03, 2022 at 09:21:22PM +0800, Michal Hocko wrote:
> On Thu 04-08-22 05:08:34, Feng Tang wrote:
> [...]
> > Do we still need the other nodemask API I proposed earlier which has
> > no parameter of gfp_flag, and used for __nr_hugepages_store_common?
>
> I would touch as little code as possible.
OK.
Please review the following patch, thanks! - Feng
---
>From a2db9a57da616bb3ea21e48a4a9ceb5c2cf4f7a2 Mon Sep 17 00:00:00 2001
From: Feng Tang <feng.tang@...el.com>
Date: Thu, 4 Aug 2022 09:39:24 +0800
Subject: [PATCH RFC] 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")
[1], the policy_nodemask_current()'s semantics for this new policy
has been changed, which returns 'preferred' nodes instead of 'allowed'
nodes, and could hurt the usage of its caller in hugetlb:
allowed_mems_nr().
Michal found the policy_nodemask_current() is only used by hugetlb,
and suggested to move it to hugetlb code with more explicit name to
enforce the 'allowed' semantics for which only MPOL_BIND policy
matters.
One note for the new policy_mbind_nodemask() is, the cross check
from MPOL_BIND, gfp flags and cpuset configuration can lead to
a no available node case, which is considered to be broken
configuration and 'NULL' (equals all nodes) is returned.
[1]. https://lore.kernel.org/lkml/20220801084207.39086-1-songmuchun@bytedance.com/t/
Reported-by: Muchun Song <songmuchun@...edance.com>
Suggested-by: Michal Hocko <mhocko@...e.com>
Signed-off-by: Feng Tang <feng.tang@...el.com>
---
include/linux/mempolicy.h | 32 ++++++++++++++++++++------------
mm/hugetlb.c | 24 ++++++++++++++++++++----
mm/mempolicy.c | 20 --------------------
3 files changed, 40 insertions(+), 36 deletions(-)
diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 668389b4b53d..ea0168fffb4c 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -151,13 +151,6 @@ extern bool mempolicy_in_oom_domain(struct task_struct *tsk,
const nodemask_t *mask);
extern nodemask_t *policy_nodemask(gfp_t gfp, struct mempolicy *policy);
-static inline nodemask_t *policy_nodemask_current(gfp_t gfp)
-{
- struct mempolicy *mpol = get_task_policy(current);
-
- return policy_nodemask(gfp, mpol);
-}
-
extern unsigned int mempolicy_slab_node(void);
extern enum zone_type policy_zone;
@@ -189,6 +182,26 @@ static inline bool mpol_is_preferred_many(struct mempolicy *pol)
return (pol->mode == MPOL_PREFERRED_MANY);
}
+static inline int apply_policy_zone(struct mempolicy *policy, enum zone_type zone)
+{
+ enum zone_type dynamic_policy_zone = policy_zone;
+
+ BUG_ON(dynamic_policy_zone == ZONE_MOVABLE);
+
+ /*
+ * if policy->nodes has movable memory only,
+ * we apply policy when gfp_zone(gfp) = ZONE_MOVABLE only.
+ *
+ * policy->nodes is intersect with node_states[N_MEMORY].
+ * so if the following test fails, it implies
+ * policy->nodes has movable memory only.
+ */
+ if (!nodes_intersects(policy->nodes, node_states[N_HIGH_MEMORY]))
+ dynamic_policy_zone = ZONE_MOVABLE;
+
+ return zone >= dynamic_policy_zone;
+}
+
#else
@@ -294,11 +307,6 @@ static inline void mpol_put_task_policy(struct task_struct *task)
{
}
-static inline nodemask_t *policy_nodemask_current(gfp_t gfp)
-{
- return NULL;
-}
-
static inline bool mpol_is_preferred_many(struct mempolicy *pol)
{
return false;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a18c071c294e..ad84bb85b6de 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];
}
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index d39b01fd52fe..5553bd53927f 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1805,26 +1805,6 @@ bool vma_policy_mof(struct vm_area_struct *vma)
return pol->flags & MPOL_F_MOF;
}
-static int apply_policy_zone(struct mempolicy *policy, enum zone_type zone)
-{
- enum zone_type dynamic_policy_zone = policy_zone;
-
- BUG_ON(dynamic_policy_zone == ZONE_MOVABLE);
-
- /*
- * if policy->nodes has movable memory only,
- * we apply policy when gfp_zone(gfp) = ZONE_MOVABLE only.
- *
- * policy->nodes is intersect with node_states[N_MEMORY].
- * so if the following test fails, it implies
- * policy->nodes has movable memory only.
- */
- if (!nodes_intersects(policy->nodes, node_states[N_HIGH_MEMORY]))
- dynamic_policy_zone = ZONE_MOVABLE;
-
- return zone >= dynamic_policy_zone;
-}
-
/*
* Return a nodemask representing a mempolicy for filtering nodes for
* page allocation
--
2.27.0
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