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Commit ac924c60 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
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[PATCH] setup_per_zone_pages_min() overflow fix 

As pointed out in http://bugzilla.kernel.org/show_bug.cgi?id=6490

, this
function can experience overflows on 32-bit machines, causing our response to
changed values of min_free_kbytes to go whacky.

Fixing it efficiently is all too hard, so fix it with 64-bit math instead.

Cc: Ake Sandgren <ake.sandgren@hpc2n.umu.se>
Cc: Martin Bligh <mbligh@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 5afdbd6e

mm/page_alloc.c

+7 −4
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ 
#include <linux/mempolicy.h>



#include <asm/tlbflush.h>

#include <asm/div64.h>

#include "internal.h"



/*
@@ -2566,9 +2567,11 @@ void setup_per_zone_pages_min(void) 
	}



	for_each_zone(zone) {

		unsigned long tmp;

		u64 tmp;



		spin_lock_irqsave(&zone->lru_lock, flags);

		tmp = (pages_min * zone->present_pages) / lowmem_pages;

		tmp = (u64)pages_min * zone->present_pages;

		do_div(tmp, lowmem_pages);

		if (is_highmem(zone)) {

			/*

			 * __GFP_HIGH and PF_MEMALLOC allocations usually don't
@@ -2595,8 +2598,8 @@ void setup_per_zone_pages_min(void) 
			zone->pages_min = tmp;

		}



		zone->pages_low   = zone->pages_min + tmp / 4;

		zone->pages_high  = zone->pages_min + tmp / 2;

		zone->pages_low   = zone->pages_min + (tmp >> 2);

		zone->pages_high  = zone->pages_min + (tmp >> 1);

		spin_unlock_irqrestore(&zone->lru_lock, flags);

	}