On 10 Apr 2017, at 17:09, Andrew Morton wrote: > On Mon, 10 Apr 2017 19:07:14 +0100 Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: > >> On Mon, Apr 10, 2017 at 12:49:40PM -0500, Zi Yan wrote: >>> On 10 Apr 2017, at 12:20, Mel Gorman wrote: >>> >>>> On Mon, Apr 10, 2017 at 11:45:08AM -0500, Zi Yan wrote: >>>>>> While this could be fixed with heavy locking, it's only necessary to >>>>>> make a copy of the PMD on the stack during change_pmd_range and avoid >>>>>> races. A new helper is created for this as the check if quite subtle and the >>>>>> existing similar helpful is not suitable. This passed 154 hours of testing >>>>>> (usually triggers between 20 minutes and 24 hours) without detecting bad >>>>>> PMDs or corruption. A basic test of an autonuma-intensive workload showed >>>>>> no significant change in behaviour. >>>>>> >>>>>> Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> >>>>>> Cc: stable@xxxxxxxxxxxxxxx >>>>> >>>>> Does this patch fix the same problem fixed by Kirill's patch here? >>>>> https://lkml.org/lkml/2017/3/2/347 >>>>> >>>> >>>> I don't think so. The race I'm concerned with is due to locks not being >>>> held and is in a different path. >>> >>> I do not agree. Kirill's patch is fixing the same race problem but in >>> zap_pmd_range(). >>> >>> The original autoNUMA code first clears PMD then sets it to protnone entry. >>> pmd_trans_huge() does not return TRUE because it saw cleared PMD, but >>> pmd_none_or_clear_bad() later saw the protnone entry and reported it as bad. >>> Is this the problem you are trying solve? >>> >>> Kirill's patch will pmdp_invalidate() the PMD entry, which keeps _PAGE_PSE bit, >>> so pmd_trans_huge() will return TRUE. In this case, it also fixes >>> your race problem in change_pmd_range(). >>> >>> Let me know if I miss anything. >>> >> >> Ok, now I see. I think you're correct and I withdraw the patch. > > I have Kirrill's > > thp-reduce-indentation-level-in-change_huge_pmd.patch > thp-fix-madv_dontneed-vs-numa-balancing-race.patch > mm-drop-unused-pmdp_huge_get_and_clear_notify.patch > thp-fix-madv_dontneed-vs-madv_free-race.patch > thp-fix-madv_dontneed-vs-madv_free-race-fix.patch > thp-fix-madv_dontneed-vs-clear-soft-dirty-race.patch > > scheduled for 4.12-rc1. It sounds like > thp-fix-madv_dontneed-vs-madv_free-race.patch and > thp-fix-madv_dontneed-vs-madv_free-race.patch need to be boosted to > 4.11 and stable? thp-fix-madv_dontneed-vs-numa-balancing-race.patch is the fix for numa balancing problem reported in this thread. mm-drop-unused-pmdp_huge_get_and_clear_notify.patch, thp-fix-madv_dontneed-vs-madv_free-race.patch, thp-fix-madv_dontneed-vs-madv_free-race-fix.patch, and thp-fix-madv_dontneed-vs-clear-soft-dirty-race.patch are the fixes for other potential race problems similar to this one. I think it is better to have all these patches applied. -- Best Regards Yan Zi
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