Messages in this thread | | | Date | Mon, 26 Apr 2010 18:28:38 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [BUGFIX][mm][PATCH] fix migration race in rmap_walk |
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On Mon, 26 Apr 2010 08:49:01 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> On Sat, 24 Apr 2010 11:43:24 +0100 > Mel Gorman <mel@csn.ul.ie> wrote:
> > It looks nice but it still broke after 28 hours of running. The > > seq-counter is still insufficient to catch all changes that are made to > > the list. I'm beginning to wonder if a) this really can be fully safely > > locked with the anon_vma changes and b) if it has to be a spinlock to > > catch the majority of cases but still a lazy cleanup if there happens to > > be a race. It's unsatisfactory and I'm expecting I'll either have some > > insight to the new anon_vma changes that allow it to be locked or Rik > > knows how to restore the original behaviour which as Andrea pointed out > > was safe. > > > Ouch.
Ok, reproduced. Here is status in my test + printk().
* A race doesn't seem to happen if swap=off. I need to swapon to cause the bug. * Before unmap, mapcount=1, SwapCache for anonymous memory. old page's flag was SWAPCACHE, Active, Uptodate, Referenced, Locked. * After remap, mapcount=0, return code=0. new page's flag after remap was SwapCache, Active, Dirty, Uptodate, Referenced.
(Hmm, dirty bit can be added by try_to_unamp().)
-Kame
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