linux-kernel - Re: [PATCH 2/3] mm: Consolidate vma destruction into remove

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Date:	Mon, 27 Sep 2010 09:39:46 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Rik van Riel <riel@...hat.com>,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH 2/3] mm: Consolidate vma destruction into remove_vma.

(Fixing Hugh's email address.)

On Mon, Sep 27, 2010 at 9:37 AM, Pekka Enberg <penberg@...nel.org> wrote:
> Hi Eric,
>
> On Sun, Sep 26, 2010 at 2:34 AM, Eric W. Biederman
> <ebiederm@...ssion.com> wrote:
>> Consolidate vma destruction in remove_vma.   This is slightly
>> better for code size and for code maintenance.  Avoiding the pain
>> of 3 copies of everything needed to tear down a vma.
>>
>> Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>
>> ---
>>  mm/mmap.c |   21 +++++----------------
>>  1 files changed, 5 insertions(+), 16 deletions(-)
>>
>> diff --git a/mm/mmap.c b/mm/mmap.c
>> index 6128dc8..17dd003 100644
>> --- a/mm/mmap.c
>> +++ b/mm/mmap.c
>> @@ -643,16 +643,10 @@ again:                    remove_next = 1 + (end > next->vm_end);
>>                spin_unlock(&mapping->i_mmap_lock);
>>
>>        if (remove_next) {
>> -               if (file) {
>> -                       fput(file);
>> -                       if (next->vm_flags & VM_EXECUTABLE)
>> -                               removed_exe_file_vma(mm);
>> -               }
>>                if (next->anon_vma)
>>                        anon_vma_merge(vma, next);
>> +               remove_vma(next);
>
> remove_vma() does vma->vm_ops->close() but we don't do that here. Are
> you sure the conversion is safe?
>
>>                mm->map_count--;
>> -               mpol_put(vma_policy(next));
>> -               kmem_cache_free(vm_area_cachep, next);
>>                /*
>>                 * In mprotect's case 6 (see comments on vma_merge),
>>                 * we must remove another next too. It would clutter
>
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