Messages in this thread | | | Subject | Re: [PATCH v3 2/2] mm: hugetlb: soft-offline: dissolve_free_huge_page() return zero on !PageHuge | From | Mike Kravetz <> | Date | Tue, 18 Jun 2019 10:55:27 -0700 |
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On 6/17/19 1:51 AM, Naoya Horiguchi wrote: > madvise(MADV_SOFT_OFFLINE) often returns -EBUSY when calling soft offline > for hugepages with overcommitting enabled. That was caused by the suboptimal > code in current soft-offline code. See the following part: > > ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL, > MIGRATE_SYNC, MR_MEMORY_FAILURE); > if (ret) { > ... > } else { > /* > * We set PG_hwpoison only when the migration source hugepage > * was successfully dissolved, because otherwise hwpoisoned > * hugepage remains on free hugepage list, then userspace will > * find it as SIGBUS by allocation failure. That's not expected > * in soft-offlining. > */ > ret = dissolve_free_huge_page(page); > if (!ret) { > if (set_hwpoison_free_buddy_page(page)) > num_poisoned_pages_inc(); > } > } > return ret; > > Here dissolve_free_huge_page() returns -EBUSY if the migration source page > was freed into buddy in migrate_pages(), but even in that case we actually > has a chance that set_hwpoison_free_buddy_page() succeeds. So that means > current code gives up offlining too early now. > > dissolve_free_huge_page() checks that a given hugepage is suitable for > dissolving, where we should return success for !PageHuge() case because > the given hugepage is considered as already dissolved. > > This change also affects other callers of dissolve_free_huge_page(), > which are cleaned up together. > > Reported-by: Chen, Jerry T <jerry.t.chen@intel.com> > Tested-by: Chen, Jerry T <jerry.t.chen@intel.com> > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Thanks,
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
-- Mike Kravetz
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