Re: [PATCH] mm: fix page_lock_anon_vma leaving mutex locked

[Linus Torvalds]

On Sat, May 28, 2011 at 3:02 PM, Hugh Dickins <hughd@xxxxxxxxxx> wrote:
>
> But I'm replying before I've given it enough thought,
> mainly to let you know that I am back on it now.

So I applied your other two patches as obvious, but not this one.

I'm wondering - wouldn't it be nicer to just re-check (after getting
the anon_vma lock) that page->mapping still matches anon_mapping?

That said, I do agree with the "anon_vma_root" part of your patch. I
just think you mixed up two independent issues with it: the fact that
we may be unlocking a new root, and the precise check used to
determine whether the anon_vma might have changed.

So my gut feeling is that we should do the "anon_vma" root thing
independently as a fix for the "maybe anon_vma->root changed" issue,
and then as a separate patch decide on how to check whether anon_vma
is still valid.

Hmm?

                   Linus
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