On Wed, 28 Apr 2010 00:58:52 +0200 Andrea Arcangeli <aarcange@xxxxxxxxxx> wrote: > On Wed, Apr 28, 2010 at 12:30:04AM +0200, Andrea Arcangeli wrote: > > I'll now evaluate the fix and see if I can find any other > > way to handle this. > > > I think a better fix for bug mentioned in patch 3, is like below. This > seems to work fine on aa.git with the old (stable) 2.6.33 anon-vma > code. Not sure if this also works with the new anon-vma code in > mainline but at first glance I think it should. At that point we > should be single threaded so it shouldn't matter if anon_vma is > temporary null. > > Then you've to re-evaluate the vma_adjust fixes for mainline-only in > patch 2 at the light of the below (I didn't check patch 2 in detail). > > Please try to reproduce with the below applied. > > ---- > Subject: fix race between shift_arg_pages and rmap_walk > > From: Andrea Arcangeli <aarcange@xxxxxxxxxx> > > migrate.c requires rmap to be able to find all ptes mapping a page at > all times, otherwise the migration entry can be instantiated, but it > can't be removed if the second rmap_walk fails to find the page. > > So shift_arg_pages must run atomically with respect of rmap_walk, and > it's enough to run it under the anon_vma lock to make it atomic. > > And split_huge_page() will have the same requirements as migrate.c > already has. > > Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> Seems nice. I'll test this but I think we need to take care of do_mremap(), too. And it's more complicated.... Thanks, -Kame -- 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>