> On Oct 20, 2019, at 11:16 PM, Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> wrote: > > On Fri, Oct 18, 2019 at 07:56:09AM -0400, Qian Cai wrote: >> >> >> On Oct 18, 2019, at 2:35 AM, Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> >> wrote: >> >> >> You're right, then I don't see how this happens. If the error hugepage was >> isolated without having PG_hwpoison set, it's unexpected and problematic. >> I'm testing myself with v5.4-rc2 (simply ran move_pages12 and did hotremove >> /hotadd) >> but don't reproduce the issue yet. Do we need specific kernel version/ >> config >> to trigger this? >> >> >> This is reproducible on linux-next with the config. Not sure if it is >> reproducible on x86. >> >> https://raw.githubusercontent.com/cailca/linux-mm/master/powerpc.config >> >> and kernel cmdline if that matters >> >> page_poison=on page_owner=on numa_balancing=enable \ >> systemd.unified_cgroup_hierarchy=1 debug_guardpage_minorder=1 \ >> page_alloc.shuffle=1 > > Thanks for the info. > >> >> BTW, where does the code set PG_hwpoison for the head page? > > Precisely speaking, soft offline only sets PG_hwpoison after the target > hugepage is successfully dissolved (then it's not a hugepage any more), > so PG_hwpoison is set on the raw page in set_hwpoison_free_buddy_page(). > > In move_pages12 case, madvise(MADV_SOFT_OFFLINE) is called for the range > of 2 hugepages, so the expected result is that page offset 0 and 512 > are marked as PG_hwpoison after injection. > > Looking at your dump_page() output, the end_pfn is page offset 1 > ("page:c00c000800458040" is likely to point to pfn 0x11601.) > The page belongs to high order buddy free page, but doesn't have > PageBuddy nor PageHWPoison because it was not the head page or > the raw error page. > >> Unfortunately, this does not solve the problem. It looks to me that in >> soft_offline_huge_page(), set_hwpoison_free_buddy_page() will only set >> PG_hwpoison for buddy pages, so the even the compound_head() has no PG_hwpoison >> set. > > Your analysis is totally correct, and this behavior will be fixed by > the change (https://lkml.org/lkml/2019/10/17/551) in Oscar's rework. > The raw error page will be taken off from buddy system and the other > subpages are properly split into lower orderer pages (we'll properly > manage PageBuddy flags). So all possible cases would be covered by > branches in __test_page_isolated_in_pageblock. Naoya, Oscar, it looks like this series was stuck. https://lkml.org/lkml/2019/10/17/551 I can still reproduce this issue as today. Maybe it is best we could post a single patch (which one?) to fix the loop first?
