On Thu, Apr 29, 2010 at 05:32:17PM +0900, Minchan Kim wrote:
> 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);
> ---
>
I'm blind. You're right.
> But we still need patch about shift_arg_pages.
>
Assuming you are referring to migration, it's easiest to just not migrate
pages within the stack until after shift_arg_pages runs. The locks
cannot be held during move_page_tables() because the page allocator is
called. It could be done in two stages where pages are allocated outside
the lock and then passed to move_page_tables() but I don't think
increasing the cost of exec() is justified just so a page can be
migrated during exec.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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