linux-kernel - Re: [RFC PATCH -v3] take all anon_vma locks in anon_vma

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Date:	Thu, 29 Apr 2010 17:32:17 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Christoph Lameter <cl@...ux.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH -v3] take all anon_vma locks in anon_vma_lock

On Thu, 2010-04-29 at 09:15 +0100, Mel Gorman wrote:
> On Wed, Apr 28, 2010 at 04:57:34PM -0400, Rik van Riel wrote:
> > Take all the locks for all the anon_vmas in anon_vma_lock, this properly
> > excludes migration and the transparent hugepage code from VMA changes done
> > by mmap/munmap/mprotect/expand_stack/etc...
> > 
> 
> In vma_adjust(), what prevents something like rmap_map seeing partial
> updates while the following lines execute?
> 
>         vma->vm_start = start;
>         vma->vm_end = end;
>         vma->vm_pgoff = pgoff;
>         if (adjust_next) {
>                 next->vm_start += adjust_next << PAGE_SHIFT;
>                 next->vm_pgoff += adjust_next;
>         }
> They would appear to happen outside the lock, even with this patch. The
> update happened within the lock in 2.6.33.
> 
> 
> 
This part does it. :)

----
@@ -578,6 +578,7 @@ again:                      remove_next = 1 + (end >
next->vm_end);
                }   
        }   
 
+       anon_vma_lock(vma, &mm->mmap_sem);
        if (root) {
                flush_dcache_mmap_lock(mapping);
                vma_prio_tree_remove(vma, root);
@@ -599,6 +600,7 @@ again:                      remove_next = 1 + (end >
next->vm_end);
                vma_prio_tree_insert(vma, root);
                flush_dcache_mmap_unlock(mapping);
        }   
+       anon_vma_unlock(vma);
---


But we still need patch about shift_arg_pages.



-- 
Kind regards,
Minchan Kim


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