Re: [PATCH 2/2] mm,migration: Avoid race between shift_arg_pages()and rmap_walk() during migration by not migrating temporary stacks

[Andrea Arcangeli]

Hi Mel,

did you see my proposed fix? I'm running with it applied, I'd be
interested if you can test it. Surely it will also work for new
anon-vma code in upstream, because at that point there's just 1
anon-vma and nothing else attached to the vma.

http://git.kernel.org/?p=linux/kernel/git/andrea/aa.git;a=commit;h=6efa1dfa5152ef8d7f26beb188d6877525a9dd03

I think it's wrong to try to handle the race in rmap walk by making
magic checks on vm_flags VM_GROWSDOWN|GROWSUP and
vma->vm_mm->map_count == 1, when we can fix it fully and simply in
exec.c by indexing two vmas in the same anon-vma with a different
vm_start so the pages will be found at all times by the rmap_walk.
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