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[PATCH 1/1] MIPS: Fix "max_mapnr" assignment bug

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Subject: [PATCH 1/1] MIPS: Fix "max_mapnr" assignment bug
From: "Williams, Victor L." <>
Date: Wed, 13 Aug 2008 15:21:37 -0400
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Thread-topic: [PATCH 1/1] MIPS: Fix "max_mapnr" assignment bug

Fix "max_mapnr" assignment bug for high-memory enabled kernels running on
platforms with no high memory

Currently, high memory enabled kernels always set "max_mapnr" equal to
"highend_pfn", but "highend_pfn" is only valid if high memory is available on
the platform.  The proposed fix is to only use "highend_pfn" in the assignment
when it is valid (non-zero).  In my particular case, this bug was manifesting
itself via the "pfn_valid()" macro, with "CONFIG_FLATMEM" defined.

Signed-off-by: Victor Williams <>
Signed-off-by: Sudharsan Vijayaraghavan <>

 init.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- old/arch/mips/mm/init.c     2008-08-06 11:19:01.000000000 -0500
+++ new/arch/mips/mm/init.c     2008-08-13 11:17:03.000000000 -0500
@@ -388,13 +388,13 @@
        unsigned long codesize, reservedpages, datasize, initsize;
        unsigned long tmp, ram;

+       max_mapnr = max_low_pfn;
 #error "CONFIG_HIGHMEM and CONFIG_DISCONTIGMEM dont work together yet"
-       max_mapnr = highend_pfn;
-       max_mapnr = max_low_pfn;
+       if (highend_pfn)
+          max_mapnr = highend_pfn;
        high_memory = (void *) __va(max_low_pfn << PAGE_SHIFT);

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