On 04/11/2017 12:28 AM, Zi Yan wrote: > 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. Yeah we should get all such fixes to stable IMHO (after review :). It's not the first time that a fix for MADV_DONTNEED turned out to also fix a race that involved "normal operation" with THP, without such syscalls. > -- > Best Regards > Yan Zi > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
