Messages in this thread | | | Date | Fri, 7 May 2010 10:57:12 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH 2/2] mm,migration: Fix race between shift_arg_pages and rmap_walk by guaranteeing rmap_walk finds PTEs created within the temporary stack |
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On Thu, 6 May 2010 18:40:39 -0700 (PDT) Linus Torvalds <torvalds@linux-foundation.org> wrote:
> > > On Fri, 7 May 2010, Mel Gorman wrote: > > > > Page migration requires rmap to be able to find all migration ptes > > created by migration. If the second rmap_walk clearing migration PTEs > > misses an entry, it is left dangling causing a BUG_ON to trigger during > > fault. For example; > > So I still absolutely detest this patch. > > Why didn't the other - much simpler - patch work? The one Rik pointed to: > > http://lkml.org/lkml/2010/4/30/198 > > and didn't do that _disgusting_ temporary anon_vma? > I vote for simple one rather than temporal anon_vma. IIUC, this patch is selected for not to leak exec's problem out to mm/ by magical check.
> Alternatively, why don't we just take the anon_vma lock over this region, > so that rmap can't _walk_ the damn thing? >
IIUC, move_page_tables() may call "page table allocation" and it cannot be done under spinlock.
Thanks, -Kame
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