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Date: Fri, 11 Nov 2011 18:24:58 +0100
From: Andrea Arcangeli <aarcange@...hat.com>
To: Hillf Danton <dhillf@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Hugh Dickins <hughd@...gle.com>,
Johannes Weiner <jweiner@...hat.com>,
LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: [PATCH] mmap: fix loop when adjusting vma
On Fri, Nov 11, 2011 at 08:53:23PM +0800, Hillf Danton wrote:
> --- a/mm/mmap.c Fri Nov 11 20:35:46 2011
> +++ b/mm/mmap.c Fri Nov 11 20:41:32 2011
> @@ -490,6 +490,7 @@ __vma_unlink(struct mm_struct *mm, struc
> int vma_adjust(struct vm_area_struct *vma, unsigned long start,
> unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
> {
> + unsigned long saved_end = end;
> struct mm_struct *mm = vma->vm_mm;
> struct vm_area_struct *next = vma->vm_next;
> struct vm_area_struct *importer = NULL;
> @@ -634,7 +635,14 @@ again: remove_next = 1 + (end > next->
> */
> if (remove_next == 2) {
> next = vma->vm_next;
> - goto again;
> + if (next) {
> + /*
> + * we have more work, reload @end in case
> + * it is clobbered.
> + */
> + end = saved_end;
> + goto again;
> + }
> }
Doesn't matter if it's clobbered, remove_next will be set to 1 and
that's all we care about. Caller should use vma->vm_next->vm_end as
"end" anyway for case 6 so it wouldn't be set to 2. Also next can't be
NULL if remove_next == 2. So I don't think this is necessary.
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