patches.dma-mapping/mm-serialize-access-to-min_free_kbytes.patch

From dhobsong@igel.co.jp Mon Oct 29 00:52:10 2012
From: Damian Hobson-Garcia <dhobsong@igel.co.jp>
Date: Mon, 29 Oct 2012 16:50:27 +0900
Subject: [PATCH v2 10/58] mm: Serialize access to min_free_kbytes
To: greg@kroah.com, laurent.pinchart@ideasonboard.com, horms@verge.net.au
Cc: ltsi-dev@lists.linuxfoundation.org, dhobsong@igel.co.jp
Message-ID: <1351497075-32717-11-git-send-email-dhobsong@igel.co.jp>


From: Mel Gorman <mgorman@suse.de>

There is a race between the min_free_kbytes sysctl, memory hotplug
and transparent hugepage support enablement.  Memory hotplug uses a
zonelists_mutex to avoid a race when building zonelists. Reuse it to
serialise watermark updates.

[a.p.zijlstra@chello.nl: Older patch fixed the race with spinlock]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: Barry Song <Baohua.Song@csr.com>
(cherry picked from commit cfd3da1e49bb95c355c01c0f502d657deb3d34a4)

Signed-off-by: Damian Hobson-Garcia <dhobsong@igel.co.jp>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 mm/page_alloc.c |   23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5027,14 +5027,7 @@ static void setup_per_zone_lowmem_reserv
 	calculate_totalreserve_pages();
 }
 
-/**
- * setup_per_zone_wmarks - called when min_free_kbytes changes
- * or when memory is hot-{added|removed}
- *
- * Ensures that the watermark[min,low,high] values for each zone are set
- * correctly with respect to min_free_kbytes.
- */
-void setup_per_zone_wmarks(void)
+static void __setup_per_zone_wmarks(void)
 {
 	unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
 	unsigned long lowmem_pages = 0;
@@ -5089,6 +5082,20 @@ void setup_per_zone_wmarks(void)
 	calculate_totalreserve_pages();
 }
 
+/**
+ * setup_per_zone_wmarks - called when min_free_kbytes changes
+ * or when memory is hot-{added|removed}
+ *
+ * Ensures that the watermark[min,low,high] values for each zone are set
+ * correctly with respect to min_free_kbytes.
+ */
+void setup_per_zone_wmarks(void)
+{
+	mutex_lock(&zonelists_mutex);
+	__setup_per_zone_wmarks();
+	mutex_unlock(&zonelists_mutex);
+}
+
 /*
  * The inactive anon list should be small enough that the VM never has to
  * do too much work, but large enough that each inactive page has a chance