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SubjectRe: [patch 1/1] MM: detach_vmas_to_be_unmapped fix


Ingo Oeser wrote:
> Hi,
>
> On Wednesday, 21. February 2007, akuster@mvista.com wrote:
>> ---
>>
>> mm/mmap.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff -puN mm/mmap.c~Avoiding-mmap-fragmentation_fixup mm/mmap.c
>> --- linux-2.6_clean/mm/mmap.c~Avoiding-mmap-fragmentation_fixup 2007-02-21 09:49:32.000000000 -0800
>> +++ linux-2.6_clean-akuster/mm/mmap.c 2007-02-21 09:51:26.000000000 -0800
>> @@ -1720,9 +1720,9 @@ detach_vmas_to_be_unmapped(struct mm_str
>> *insertion_point = vma;
>> tail_vma->vm_next = NULL;
>> if (mm->unmap_area == arch_unmap_area)
>> - addr = prev ? prev->vm_end : mm->mmap_base;
>> + addr = prev ? prev->vm_start : mm->mmap_base;
>> else
>> - addr = vma ? vma->vm_start : mm->mmap_base;
>> + addr = vma ? vma->vm_end : mm->mmap_base;
>> mm->unmap_area(mm, addr);
>> mm->mmap_cache = NULL; /* Kill the cache. */
>> }
>
> Please comment, why you think this is necessary.

Yes that would help.

On Feb. 16th I asked a question and got no response. Here is what should
have been included with the above patch.

Wolfgang Wander submitted a fix to address a mmap fragmentation issue.
The git patch ( 1363c3cd8603a913a27e2995dccbd70d5312d8e6 ) is somewhat
different and yields different results when running Wolfgang's test case
leakme.c.

IMHO, the vm start and end address are swapped in arch_unmap_area and
arch_unmap_area_topdown functions.

Prior to this patch arch_unmap_area() used area->vm_start and
arch_unmap_area_topdown used area->vm_end in the git patch the following
change showed up.

if (mm->unmap_area == arch_unmap_area)
addr = prev ? prev->vm_start : mm->mmap_base;
else
addr = vma ? vma->vm_end : mm->mmap_base;

Using Wolfgang Wander's leakme.c test, I get the same results seen with
his original "Avoiding mmap fragmentation" patch as I do after swapping
the start & end address in the above code segment. The patch I
submitted addresses this typo issue.

TIA,
Armin

>
>
> Thanks & Regards
>
> Ingo Oeser
-
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