[RFC][PATCH 3/6] mm: serialize access to min_free_kbytes

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

[-- Attachment #1: setup_per_zone_pages_min.patch --]
[-- Type: text/plain, Size: 2139 bytes --]

There is a small race between the procfs caller and the memory hotplug caller
of setup_per_zone_pages_min(). Not a big deal, but the next patch will add yet
another caller. Time to close the gap.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 mm/page_alloc.c |   16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

Index: linux-2.6-git/mm/page_alloc.c
===================================================================
--- linux-2.6-git.orig/mm/page_alloc.c	2006-11-20 13:45:27.000000000 +0100
+++ linux-2.6-git/mm/page_alloc.c	2006-11-20 13:47:39.000000000 +0100
@@ -101,6 +101,7 @@ static char *zone_names[MAX_NR_ZONES] = 
 #endif
 };
 
+static DEFINE_SPINLOCK(min_free_lock);
 int min_free_kbytes = 1024;
 
 unsigned long __meminitdata nr_kernel_pages;
@@ -2806,12 +2807,12 @@ static void setup_per_zone_lowmem_reserv
 }
 
 /**
- * setup_per_zone_pages_min - called when min_free_kbytes changes.
+ * __setup_per_zone_pages_min - called when min_free_kbytes changes.
  *
  * Ensures that the pages_{min,low,high} values for each zone are set correctly
  * with respect to min_free_kbytes.
  */
-void setup_per_zone_pages_min(void)
+static void __setup_per_zone_pages_min(void)
 {
 	unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
 	unsigned long lowmem_pages = 0;
@@ -2865,6 +2866,15 @@ void setup_per_zone_pages_min(void)
 	calculate_totalreserve_pages();
 }
 
+void setup_per_zone_pages_min(void)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&min_free_lock, flags);
+	__setup_per_zone_pages_min();
+	spin_unlock_irqrestore(&min_free_lock, flags);
+}
+
 /*
  * Initialise min_free_kbytes.
  *
@@ -2900,7 +2910,7 @@ static int __init init_per_zone_pages_mi
 		min_free_kbytes = 128;
 	if (min_free_kbytes > 65536)
 		min_free_kbytes = 65536;
-	setup_per_zone_pages_min();
+	__setup_per_zone_pages_min();
 	setup_per_zone_lowmem_reserve();
 	return 0;
 }

--

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