From: Mel Gorman <mel@csn.ul.ie>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
Christoph Lameter <cl@linux-foundation.org>,
Adam Litke <agl@us.ibm.com>, Avi Kivity <avi@redhat.com>,
David Rientjes <rientjes@google.com>,
Minchan Kim <minchan.kim@gmail.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Rik van Riel <riel@redhat.com>, Mel Gorman <mel@csn.ul.ie>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH 01/11] mm,migration: Take a reference to the anon_vma before migrating
Date: Tue, 23 Mar 2010 12:25:36 +0000 [thread overview]
Message-ID: <1269347146-7461-2-git-send-email-mel@csn.ul.ie> (raw)
In-Reply-To: <1269347146-7461-1-git-send-email-mel@csn.ul.ie>
rmap_walk_anon() does not use page_lock_anon_vma() for looking up and
locking an anon_vma and it does not appear to have sufficient locking to
ensure the anon_vma does not disappear from under it.
This patch copies an approach used by KSM to take a reference on the
anon_vma while pages are being migrated. This should prevent rmap_walk()
running into nasty surprises later because anon_vma has been freed.
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Rik van Riel <riel@redhat.com>
---
include/linux/rmap.h | 23 +++++++++++++++++++++++
mm/migrate.c | 12 ++++++++++++
mm/rmap.c | 10 +++++-----
3 files changed, 40 insertions(+), 5 deletions(-)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index d25bd22..567d43f 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -29,6 +29,9 @@ struct anon_vma {
#ifdef CONFIG_KSM
atomic_t ksm_refcount;
#endif
+#ifdef CONFIG_MIGRATION
+ atomic_t migrate_refcount;
+#endif
/*
* NOTE: the LSB of the head.next is set by
* mm_take_all_locks() _after_ taking the above lock. So the
@@ -81,6 +84,26 @@ static inline int ksm_refcount(struct anon_vma *anon_vma)
return 0;
}
#endif /* CONFIG_KSM */
+#ifdef CONFIG_MIGRATION
+static inline void migrate_refcount_init(struct anon_vma *anon_vma)
+{
+ atomic_set(&anon_vma->migrate_refcount, 0);
+}
+
+static inline int migrate_refcount(struct anon_vma *anon_vma)
+{
+ return atomic_read(&anon_vma->migrate_refcount);
+}
+#else
+static inline void migrate_refcount_init(struct anon_vma *anon_vma)
+{
+}
+
+static inline int migrate_refcount(struct anon_vma *anon_vma)
+{
+ return 0;
+}
+#endif /* CONFIG_MIGRATE */
static inline struct anon_vma *page_anon_vma(struct page *page)
{
diff --git a/mm/migrate.c b/mm/migrate.c
index 88000b8..98eaaf2 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -547,6 +547,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
int rcu_locked = 0;
int charge = 0;
struct mem_cgroup *mem = NULL;
+ struct anon_vma *anon_vma = NULL;
if (!newpage)
return -ENOMEM;
@@ -603,6 +604,8 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
if (PageAnon(page)) {
rcu_read_lock();
rcu_locked = 1;
+ anon_vma = page_anon_vma(page);
+ atomic_inc(&anon_vma->migrate_refcount);
}
/*
@@ -642,6 +645,15 @@ skip_unmap:
if (rc)
remove_migration_ptes(page, page);
rcu_unlock:
+
+ /* Drop an anon_vma reference if we took one */
+ if (anon_vma && atomic_dec_and_lock(&anon_vma->migrate_refcount, &anon_vma->lock)) {
+ int empty = list_empty(&anon_vma->head);
+ spin_unlock(&anon_vma->lock);
+ if (empty)
+ anon_vma_free(anon_vma);
+ }
+
if (rcu_locked)
rcu_read_unlock();
uncharge:
diff --git a/mm/rmap.c b/mm/rmap.c
index fcd593c..578d0fe 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -248,7 +248,8 @@ static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain)
list_del(&anon_vma_chain->same_anon_vma);
/* We must garbage collect the anon_vma if it's empty */
- empty = list_empty(&anon_vma->head) && !ksm_refcount(anon_vma);
+ empty = list_empty(&anon_vma->head) && !ksm_refcount(anon_vma) &&
+ !migrate_refcount(anon_vma);
spin_unlock(&anon_vma->lock);
if (empty)
@@ -273,6 +274,7 @@ static void anon_vma_ctor(void *data)
spin_lock_init(&anon_vma->lock);
ksm_refcount_init(anon_vma);
+ migrate_refcount_init(anon_vma);
INIT_LIST_HEAD(&anon_vma->head);
}
@@ -1338,10 +1340,8 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
/*
* Note: remove_migration_ptes() cannot use page_lock_anon_vma()
* because that depends on page_mapped(); but not all its usages
- * are holding mmap_sem, which also gave the necessary guarantee
- * (that this anon_vma's slab has not already been destroyed).
- * This needs to be reviewed later: avoiding page_lock_anon_vma()
- * is risky, and currently limits the usefulness of rmap_walk().
+ * are holding mmap_sem. Users without mmap_sem are required to
+ * take a reference count to prevent the anon_vma disappearing
*/
anon_vma = page_anon_vma(page);
if (!anon_vma)
--
1.6.5
next prev parent reply other threads:[~2010-03-23 12:25 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-23 12:25 [PATCH 0/11] Memory Compaction v5 Mel Gorman
2010-03-23 12:25 ` Mel Gorman [this message]
2010-03-23 12:25 ` [PATCH 02/11] mm,migration: Do not try to migrate unmapped anonymous pages Mel Gorman
2010-03-23 17:22 ` Christoph Lameter
2010-03-23 18:04 ` Mel Gorman
2010-03-23 12:25 ` [PATCH 03/11] mm: Share the anon_vma ref counts between KSM and page migration Mel Gorman
2010-03-23 17:25 ` Christoph Lameter
2010-03-23 23:55 ` KAMEZAWA Hiroyuki
2010-03-23 12:25 ` [PATCH 04/11] Allow CONFIG_MIGRATION to be set without CONFIG_NUMA or memory hot-remove Mel Gorman
2010-03-23 12:25 ` [PATCH 05/11] Export unusable free space index via /proc/unusable_index Mel Gorman
2010-03-23 17:31 ` Christoph Lameter
2010-03-23 18:14 ` Mel Gorman
2010-03-24 0:03 ` KAMEZAWA Hiroyuki
2010-03-24 0:16 ` Minchan Kim
2010-03-24 0:13 ` KAMEZAWA Hiroyuki
2010-03-24 10:25 ` Mel Gorman
2010-03-23 12:25 ` [PATCH 06/11] Export fragmentation index via /proc/extfrag_index Mel Gorman
2010-03-23 17:37 ` Christoph Lameter
2010-03-23 12:25 ` [PATCH 07/11] Memory compaction core Mel Gorman
2010-03-23 17:56 ` Christoph Lameter
2010-03-23 18:15 ` Mel Gorman
2010-03-23 18:33 ` Christoph Lameter
2010-03-23 18:58 ` Mel Gorman
2010-03-23 19:20 ` Christoph Lameter
2010-03-24 1:03 ` KAMEZAWA Hiroyuki
2010-03-24 1:47 ` Minchan Kim
2010-03-24 1:53 ` KAMEZAWA Hiroyuki
2010-03-24 2:10 ` Minchan Kim
2010-03-24 10:57 ` Mel Gorman
2010-03-24 20:33 ` Andrew Morton
2010-03-24 20:59 ` Jonathan Corbet
2010-03-24 21:14 ` Andrew Morton
2010-03-24 21:19 ` Christoph Lameter
2010-03-24 21:19 ` Andrea Arcangeli
2010-03-24 21:28 ` Jonathan Corbet
2010-03-24 21:47 ` Andrea Arcangeli
2010-03-24 21:54 ` Jonathan Corbet
2010-03-24 22:06 ` Andrea Arcangeli
2010-03-24 21:57 ` Andrea Arcangeli
2010-03-25 9:13 ` Mel Gorman
2010-03-23 12:25 ` [PATCH 08/11] Add /proc trigger for memory compaction Mel Gorman
2010-03-23 18:25 ` Christoph Lameter
2010-03-23 18:32 ` Mel Gorman
2010-03-24 20:33 ` Andrew Morton
2010-03-26 10:46 ` Mel Gorman
2010-03-23 12:25 ` [PATCH 09/11] Add /sys trigger for per-node " Mel Gorman
2010-03-23 18:27 ` Christoph Lameter
2010-03-23 22:45 ` Minchan Kim
2010-03-24 0:19 ` KAMEZAWA Hiroyuki
2010-03-23 12:25 ` [PATCH 10/11] Direct compact when a high-order allocation fails Mel Gorman
2010-03-23 23:10 ` Minchan Kim
2010-03-24 11:11 ` Mel Gorman
2010-03-24 11:59 ` Minchan Kim
2010-03-24 12:06 ` Minchan Kim
2010-03-24 12:10 ` Mel Gorman
2010-03-24 12:09 ` Mel Gorman
2010-03-24 12:25 ` Minchan Kim
2010-03-24 1:19 ` KAMEZAWA Hiroyuki
2010-03-24 11:40 ` Mel Gorman
2010-03-25 0:30 ` KAMEZAWA Hiroyuki
2010-03-25 9:48 ` Mel Gorman
2010-03-25 9:50 ` KAMEZAWA Hiroyuki
2010-03-25 10:16 ` Mel Gorman
2010-03-26 1:03 ` KAMEZAWA Hiroyuki
2010-03-26 9:40 ` Mel Gorman
2010-03-24 20:48 ` Andrew Morton
2010-03-25 0:57 ` KAMEZAWA Hiroyuki
2010-03-25 10:21 ` Mel Gorman
2010-03-23 12:25 ` [PATCH 11/11] Do not compact within a preferred zone after a compaction failure Mel Gorman
2010-03-23 18:31 ` Christoph Lameter
2010-03-23 18:39 ` Mel Gorman
2010-03-23 19:27 ` Christoph Lameter
2010-03-24 10:37 ` Mel Gorman
2010-03-24 19:54 ` Christoph Lameter
2010-03-24 20:53 ` Andrew Morton
2010-03-25 9:40 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2010-03-12 16:41 [PATCH 0/11] Memory Compaction v4 Mel Gorman
2010-03-12 16:41 ` [PATCH 01/11] mm,migration: Take a reference to the anon_vma before migrating Mel Gorman
2010-03-14 15:01 ` Minchan Kim
2010-03-15 5:06 ` KAMEZAWA Hiroyuki
2010-03-17 1:44 ` KOSAKI Motohiro
2010-03-17 11:45 ` Mel Gorman
2010-03-17 16:38 ` Christoph Lameter
2010-03-18 11:12 ` Mel Gorman
2010-03-18 16:31 ` Christoph Lameter
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