On Wed, May 05, 2010 at 06:13:19PM +0200, Andrea Arcangeli wrote: > On Wed, May 05, 2010 at 04:54:54PM +0100, Mel Gorman wrote: > > I'm still thinking of the ordering but one possibility would be to use a mutex > > I can't take mutex in split_huge_page... so I'd need to use an other solution. > > > Not yet. > > 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. The hatchet-job mutex is off the table so it's down to start-with-root-anon_vma-and-lock-in-order-when-walking-list (what I last posted) take-all-anon_vma-locks-when-changing-vmas (Rik's) use-seq-counter-to-spot-changes-to-VMAs-when-walking-list (Kamezawa-san's approach) Any strong preference? I still haven't read the other comments Linus made so I don't have a strong preference yet. Either Rik's or the patch I posted should be enough for migration to not get tripped up as far as I can see. > 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. > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>