On 2022/10/24 14:20, Naoya Horiguchi wrote: > From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> > > HWPoisoned page is not supposed to be accessed once marked, but currently > such accesses can happen during memory hotremove because do_migrate_range() > can be called before dissolve_free_huge_pages() is called. > > Clear HPageMigratable for hwpoisoned hugepages to prevent them from being > migrated. This should be done in hugetlb_lock to avoid race against > isolate_hugetlb(). > > get_hwpoison_huge_page() needs to have a flag to show it's called from > unpoison to take refcount of hwpoisoned hugepages, so add it. > > Reported-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> > Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> > Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> > Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> > --- > ChangeLog v3 -> v7: > - introduce TESTCLEARHPAGEFLAG() to determine the value of migratable_cleared Many thanks for update, Naoya. I'm sorry but TestClearHPageMigratable() might be somewhat overkill. As we discussed in previous thread: """ I think I might be nitpicking... But it seems ClearHPageMigratable is not enough here. 1. In MF_COUNT_INCREASED case, we don't know whether HPageMigratable is set. 2. Even if HPageMigratable is set, there might be a race window before we clear HPageMigratable? So "*migratable_cleared = TestClearHPageMigratable" might be better? But I might be wrong. """ The case 2 should be a dumb problem(sorry about it). HPageMigratable() is always cleared while holding the hugetlb_lock which is already held by get_huge_page_for_hwpoison(). So the only case we should care about is case 1 and that can be handled by below more efficient pattern: if (HPageMigratable) ClearHPageMigratable() So the overhead of test and clear atomic ops can be avoided. But this is trival. Anyway, this patch still looks good to me. And my Reviewed-by tag still applies. Many thanks. Thanks, Miaohe Lin
