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authorMel Gorman <mgorman@suse.de>2012-12-21 23:10:25 +0000
committerLinus Torvalds <torvalds@linux-foundation.org>2013-01-02 17:32:13 -0800
commit42288fe366c4f1ce7522bc9f27d0bc2a81c55264 (patch)
treef881ebd4f4032e6cc8f5f848b2e61e9ff1d611af /mm/mempolicy.c
parent5439ca6b8ff8cf8d758c19eb28b617a5912904ee (diff)
downloadlinux-42288fe366c4f1ce7522bc9f27d0bc2a81c55264.tar.gz
mm: mempolicy: Convert shared_policy mutex to spinlock
Sasha was fuzzing with trinity and reported the following problem: BUG: sleeping function called from invalid context at kernel/mutex.c:269 in_atomic(): 1, irqs_disabled(): 0, pid: 6361, name: trinity-main 2 locks held by trinity-main/6361: #0: (&mm->mmap_sem){++++++}, at: [<ffffffff810aa314>] __do_page_fault+0x1e4/0x4f0 #1: (&(&mm->page_table_lock)->rlock){+.+...}, at: [<ffffffff8122f017>] handle_pte_fault+0x3f7/0x6a0 Pid: 6361, comm: trinity-main Tainted: G W 3.7.0-rc2-next-20121024-sasha-00001-gd95ef01-dirty #74 Call Trace: __might_sleep+0x1c3/0x1e0 mutex_lock_nested+0x29/0x50 mpol_shared_policy_lookup+0x2e/0x90 shmem_get_policy+0x2e/0x30 get_vma_policy+0x5a/0xa0 mpol_misplaced+0x41/0x1d0 handle_pte_fault+0x465/0x6a0 This was triggered by a different version of automatic NUMA balancing but in theory the current version is vunerable to the same problem. do_numa_page -> numa_migrate_prep -> mpol_misplaced -> get_vma_policy -> shmem_get_policy It's very unlikely this will happen as shared pages are not marked pte_numa -- see the page_mapcount() check in change_pte_range() -- but it is possible. To address this, this patch restores sp->lock as originally implemented by Kosaki Motohiro. In the path where get_vma_policy() is called, it should not be calling sp_alloc() so it is not necessary to treat the PTL specially. Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Tested-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mempolicy.c')
-rw-r--r--mm/mempolicy.c68
1 files changed, 48 insertions, 20 deletions
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 1cb200af382..e2df1c1fb41 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2132,7 +2132,7 @@ bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
*/
/* lookup first element intersecting start-end */
-/* Caller holds sp->mutex */
+/* Caller holds sp->lock */
static struct sp_node *
sp_lookup(struct shared_policy *sp, unsigned long start, unsigned long end)
{
@@ -2196,13 +2196,13 @@ mpol_shared_policy_lookup(struct shared_policy *sp, unsigned long idx)
if (!sp->root.rb_node)
return NULL;
- mutex_lock(&sp->mutex);
+ spin_lock(&sp->lock);
sn = sp_lookup(sp, idx, idx+1);
if (sn) {
mpol_get(sn->policy);
pol = sn->policy;
}
- mutex_unlock(&sp->mutex);
+ spin_unlock(&sp->lock);
return pol;
}
@@ -2328,6 +2328,14 @@ static void sp_delete(struct shared_policy *sp, struct sp_node *n)
sp_free(n);
}
+static void sp_node_init(struct sp_node *node, unsigned long start,
+ unsigned long end, struct mempolicy *pol)
+{
+ node->start = start;
+ node->end = end;
+ node->policy = pol;
+}
+
static struct sp_node *sp_alloc(unsigned long start, unsigned long end,
struct mempolicy *pol)
{
@@ -2344,10 +2352,7 @@ static struct sp_node *sp_alloc(unsigned long start, unsigned long end,
return NULL;
}
newpol->flags |= MPOL_F_SHARED;
-
- n->start = start;
- n->end = end;
- n->policy = newpol;
+ sp_node_init(n, start, end, newpol);
return n;
}
@@ -2357,9 +2362,12 @@ static int shared_policy_replace(struct shared_policy *sp, unsigned long start,
unsigned long end, struct sp_node *new)
{
struct sp_node *n;
+ struct sp_node *n_new = NULL;
+ struct mempolicy *mpol_new = NULL;
int ret = 0;
- mutex_lock(&sp->mutex);
+restart:
+ spin_lock(&sp->lock);
n = sp_lookup(sp, start, end);
/* Take care of old policies in the same range. */
while (n && n->start < end) {
@@ -2372,14 +2380,16 @@ static int shared_policy_replace(struct shared_policy *sp, unsigned long start,
} else {
/* Old policy spanning whole new range. */
if (n->end > end) {
- struct sp_node *new2;
- new2 = sp_alloc(end, n->end, n->policy);
- if (!new2) {
- ret = -ENOMEM;
- goto out;
- }
+ if (!n_new)
+ goto alloc_new;
+
+ *mpol_new = *n->policy;
+ atomic_set(&mpol_new->refcnt, 1);
+ sp_node_init(n_new, n->end, end, mpol_new);
+ sp_insert(sp, n_new);
n->end = start;
- sp_insert(sp, new2);
+ n_new = NULL;
+ mpol_new = NULL;
break;
} else
n->end = start;
@@ -2390,9 +2400,27 @@ static int shared_policy_replace(struct shared_policy *sp, unsigned long start,
}
if (new)
sp_insert(sp, new);
-out:
- mutex_unlock(&sp->mutex);
+ spin_unlock(&sp->lock);
+ ret = 0;
+
+err_out:
+ if (mpol_new)
+ mpol_put(mpol_new);
+ if (n_new)
+ kmem_cache_free(sn_cache, n_new);
+
return ret;
+
+alloc_new:
+ spin_unlock(&sp->lock);
+ ret = -ENOMEM;
+ n_new = kmem_cache_alloc(sn_cache, GFP_KERNEL);
+ if (!n_new)
+ goto err_out;
+ mpol_new = kmem_cache_alloc(policy_cache, GFP_KERNEL);
+ if (!mpol_new)
+ goto err_out;
+ goto restart;
}
/**
@@ -2410,7 +2438,7 @@ void mpol_shared_policy_init(struct shared_policy *sp, struct mempolicy *mpol)
int ret;
sp->root = RB_ROOT; /* empty tree == default mempolicy */
- mutex_init(&sp->mutex);
+ spin_lock_init(&sp->lock);
if (mpol) {
struct vm_area_struct pvma;
@@ -2476,14 +2504,14 @@ void mpol_free_shared_policy(struct shared_policy *p)
if (!p->root.rb_node)
return;
- mutex_lock(&p->mutex);
+ spin_lock(&p->lock);
next = rb_first(&p->root);
while (next) {
n = rb_entry(next, struct sp_node, nd);
next = rb_next(&n->nd);
sp_delete(p, n);
}
- mutex_unlock(&p->mutex);
+ spin_unlock(&p->lock);
}
#ifdef CONFIG_NUMA_BALANCING