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[PATCH] setup_per_zone_pages_min() overflow fix

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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: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Andrew Morton 2006-05-15 09:43:59 -07:00 committed by Linus Torvalds
parent 5afdbd6e84
commit ac924c6034
1 changed files with 7 additions and 4 deletions
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11
mm/page_alloc.c
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@ -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);
}