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Subject[PATCH 01/31] mm: serialize access to min_free_kbytes
Date
From: Peter Zijlstra <a.p.zijlstra@chello.nl> 
There is a small race between the procfs caller and the memory hotplug caller
of setup_per_zone_wmarks(). 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>
Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
---
mm/page_alloc.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
Index: mmotm/mm/page_alloc.c
===================================================================
--- mmotm.orig/mm/page_alloc.c
+++ mmotm/mm/page_alloc.c
@@ -121,6 +121,7 @@ static char * const zone_names[MAX_NR_ZO
"Movable",
};

+static DEFINE_SPINLOCK(min_free_lock);
int min_free_kbytes = 1024;

unsigned long __meminitdata nr_kernel_pages;
@@ -4448,13 +4449,13 @@ static void setup_per_zone_lowmem_reserv
}

/**
- * setup_per_zone_wmarks - called when min_free_kbytes changes
+ * __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;
@@ -4552,6 +4553,15 @@ static void __init setup_per_zone_inacti
calculate_zone_inactive_ratio(zone);
}

+void setup_per_zone_wmarks(void)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&min_free_lock, flags);
+ __setup_per_zone_wmarks();
+ spin_unlock_irqrestore(&min_free_lock, flags);
+}
+
/*
* Initialise min_free_kbytes.
*
@@ -4587,7 +4597,7 @@ static int __init init_per_zone_wmark_mi
min_free_kbytes = 128;
if (min_free_kbytes > 65536)
min_free_kbytes = 65536;
- setup_per_zone_wmarks();
+ __setup_per_zone_wmarks();
setup_per_zone_lowmem_reserve();
setup_per_zone_inactive_ratio();
return 0;

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