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Message-Id: <20221204161432.2149375-3-hezhongkun.hzk@bytedance.com>
Date: Mon, 5 Dec 2022 00:14:31 +0800
From: Zhongkun He <hezhongkun.hzk@...edance.com>
To: mhocko@...e.com, akpm@...ux-foundation.org
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, wuyun.abel@...edance.com,
Zhongkun He <hezhongkun.hzk@...edance.com>
Subject: [PATCH 2/3] mm: fix the reference of mempolicy in some functions.
There are some functions that use mempolicy in process
context, but don't reference it. Let's fix it to have
a clear life time model.
Suggested-by: Michal Hocko <mhocko@...e.com>
Signed-off-by: Zhongkun He <hezhongkun.hzk@...edance.com>
---
mm/hugetlb.c | 16 ++++++-----
mm/mempolicy.c | 78 +++++++++++++++++++++++++-------------------------
2 files changed, 48 insertions(+), 46 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 277330f40818..0c2b5233e0c9 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4353,19 +4353,19 @@ static int __init default_hugepagesz_setup(char *s)
}
__setup("default_hugepagesz=", default_hugepagesz_setup);
-static nodemask_t *policy_mbind_nodemask(gfp_t gfp)
+static nodemask_t *policy_mbind_nodemask(gfp_t gfp, struct mempolicy **mpol)
{
#ifdef CONFIG_NUMA
- struct mempolicy *mpol = get_task_policy(current);
+ *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;
+ 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;
}
@@ -4375,14 +4375,16 @@ static unsigned int allowed_mems_nr(struct hstate *h)
int node;
unsigned int nr = 0;
nodemask_t *mbind_nodemask;
+ struct mempolicy *mpol = NULL;
unsigned int *array = h->free_huge_pages_node;
gfp_t gfp_mask = htlb_alloc_mask(h);
- mbind_nodemask = policy_mbind_nodemask(gfp_mask);
+ mbind_nodemask = policy_mbind_nodemask(gfp_mask, &mpol);
for_each_node_mask(node, cpuset_current_mems_allowed) {
if (!mbind_nodemask || node_isset(node, *mbind_nodemask))
nr += array[node];
}
+ mpol_put(mpol);
return nr;
}
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index f1857ebded46..0feffb7ff01e 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -159,7 +159,7 @@ int numa_map_to_online_node(int node)
EXPORT_SYMBOL_GPL(numa_map_to_online_node);
/* Obtain a reference on the specified task mempolicy */
-static mempolicy *get_task_mpol(struct task_struct *p)
+static struct mempolicy *get_task_mpol(struct task_struct *p)
{
struct mempolicy *pol;
@@ -925,7 +925,8 @@ static void get_policy_nodemask(struct mempolicy *p, nodemask_t *nodes)
*nodes = p->nodes;
break;
case MPOL_LOCAL:
- /* return empty node mask for local allocation */killbreak;
+ /* return empty node mask for local allocation */
+ break;
default:
BUG();
}
@@ -951,7 +952,7 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask,
int err;
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma = NULL;
- struct mempolicy *pol = current->mempolicy, *pol_refcount = NULL;
+ struct mempolicy *pol;
if (flags &
~(unsigned long)(MPOL_F_NODE|MPOL_F_ADDR|MPOL_F_MEMS_ALLOWED))
@@ -966,8 +967,10 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask,
task_unlock(current);
return 0;
}
+ pol = get_task_mpol(current);
if (flags & MPOL_F_ADDR) {
+ mpol_put(pol); /* put the refcount of task mpol */
/*
* Do NOT fall back to task policy if the
* vma/shared policy at addr is NULL. We
@@ -979,27 +982,19 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask,
mmap_read_unlock(mm);
return -EFAULT;
}
- if (vma->vm_ops && vma->vm_ops->get_policy)
- pol = vma->vm_ops->get_policy(vma, addr);
- else
- pol = vma->vm_policy;
- } else if (addr)
- return -EINVAL;
+ /* obtain a reference to vma mpol. */
+ pol = __get_vma_policy(vma, addr);
+ mmap_read_unlock(mm);
+ } else if (addr) {
+ err = -EINVAL;
+ goto out;
+ }
if (!pol)
pol = &default_policy; /* indicates default behavior */
if (flags & MPOL_F_NODE) {
if (flags & MPOL_F_ADDR) {
- /*
- * Take a refcount on the mpol, because we are about to
- * drop the mmap_lock, after which only "pol" remains
- * valid, "vma" is stale.
- */
- pol_refcount = pol;
- vma = NULL;
- mpol_get(pol);
- mmap_read_unlock(mm);
err = lookup_node(mm, addr);
if (err < 0)
goto out;
@@ -1023,21 +1018,19 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask,
err = 0;
if (nmask) {
- if (mpol_store_user_nodemask(pol)) {
+ /*
+ * There is no need for a lock, since we get
+ * a reference to mpol.
+ */
+ if (mpol_store_user_nodemask(pol))
*nmask = pol->w.user_nodemask;
- } else {
- task_lock(current);
+ else
get_policy_nodemask(pol, nmask);
- task_unlock(current);
- }
}
out:
- mpol_cond_put(pol);
- if (vma)
- mmap_read_unlock(mm);
- if (pol_refcount)
- mpol_put(pol_refcount);
+ if (pol != &default_policy)
+ mpol_put(pol);
return err;
}
@@ -1923,16 +1916,18 @@ unsigned int mempolicy_slab_node(void)
if (!in_task())
return node;
- policy = current->mempolicy;
+ policy = get_task_mpol(current);
if (!policy)
return node;
switch (policy->mode) {
case MPOL_PREFERRED:
- return first_node(policy->nodes);
+ node = first_node(policy->nodes);
+ break;
case MPOL_INTERLEAVE:
- return interleave_nodes(policy);
+ node = interleave_nodes(policy);
+ break;
case MPOL_BIND:
case MPOL_PREFERRED_MANY:
@@ -1948,14 +1943,17 @@ unsigned int mempolicy_slab_node(void)
zonelist = &NODE_DATA(node)->node_zonelists[ZONELIST_FALLBACK];
z = first_zones_zonelist(zonelist, highest_zoneidx,
&policy->nodes);
- return z->zone ? zone_to_nid(z->zone) : node;
+ node = z->zone ? zone_to_nid(z->zone) : node;
+ break;
}
case MPOL_LOCAL:
- return node;
+ break;
default:
BUG();
}
+ mpol_put(policy);
+ return node;
}
/*
@@ -2379,21 +2377,23 @@ unsigned long alloc_pages_bulk_array_mempolicy(gfp_t gfp,
unsigned long nr_pages, struct page **page_array)
{
struct mempolicy *pol = &default_policy;
+ unsigned long pages;
if (!in_interrupt() && !(gfp & __GFP_THISNODE))
pol = get_task_policy(current);
if (pol->mode == MPOL_INTERLEAVE)
- return alloc_pages_bulk_array_interleave(gfp, pol,
+ pages = alloc_pages_bulk_array_interleave(gfp, pol,
nr_pages, page_array);
-
- if (pol->mode == MPOL_PREFERRED_MANY)
- return alloc_pages_bulk_array_preferred_many(gfp,
+ else if (pol->mode == MPOL_PREFERRED_MANY)
+ pages = alloc_pages_bulk_array_preferred_many(gfp,
numa_node_id(), pol, nr_pages, page_array);
-
- return __alloc_pages_bulk(gfp, policy_node(gfp, pol, numa_node_id()),
+ else
+ pages = __alloc_pages_bulk(gfp, policy_node(gfp, pol, numa_node_id()),
policy_nodemask(gfp, pol), nr_pages, NULL,
page_array);
+ mpol_put(pol);
+ return pages;
}
int vma_dup_policy(struct vm_area_struct *src, struct vm_area_struct *dst)
--
2.25.1
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