On Wed, May 05, 2010 at 04:54:54PM +0100, Mel Gorman wrote:
I can't take mutex in split_huge_page... so I'd need to use an other solution.
Rik's patch that takes the locks in the faster path is preferable to
me, it's just simpler, you know the really "strong" long is the
page->mapping/anon_vma->lock and nothing else. You've a page, you take
that lock, you're done for that very page.
Sure that means updating vm_start/vm_pgoff then requires locking all
anon_vmas that the vma registered into, but that's conceptually
simpler and it doesn't alter the page_lock_anon_vma semantics. Now I
wonder if you said the same_anon_vma is in order, but the same_vma is
not, if it's safe to lock the same_vma in list order in anon_vma_lock,
I didn't experience problems on the anon_vma_chain branch but
anon_vma_lock disables all lockdep lock inversion checking.
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