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authorMichal Hocko <mhocko@suse.com>2016-08-02 14:02:34 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-08-02 17:31:41 -0400
commit4e666314d286765a9e61818b488c7372326654ec (patch)
tree7a50291e533fcd14a2476212e71afb3feccc49ac /mm/hugetlb.c
parent649920c6ab93429b94bc7c1aa7c0e8395351be32 (diff)
mm, hugetlb: fix huge_pte_alloc BUG_ON
Zhong Jiang has reported a BUG_ON from huge_pte_alloc hitting when he runs his database load with memory online and offline running in parallel. The reason is that huge_pmd_share might detect a shared pmd which is currently migrated and so it has migration pte which is !pte_huge. There doesn't seem to be any easy way to prevent from the race and in fact seeing the migration swap entry is not harmful. Both callers of huge_pte_alloc are prepared to handle them. copy_hugetlb_page_range will copy the swap entry and make it COW if needed. hugetlb_fault will back off and so the page fault is retries if the page is still under migration and waits for its completion in hugetlb_fault. That means that the BUG_ON is wrong and we should update it. Let's simply check that all present ptes are pte_huge instead. Link: http://lkml.kernel.org/r/20160721074340.GA26398@dhcp22.suse.cz Signed-off-by: Michal Hocko <mhocko@suse.com> Reported-by: zhongjiang <zhongjiang@huawei.com> Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/hugetlb.c')
-rw-r--r--mm/hugetlb.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 619e00d82c5d..ef968306fd5b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4310,7 +4310,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
pte = (pte_t *)pmd_alloc(mm, pud, addr);
}
}
- BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte));
+ BUG_ON(pte && pte_present(*pte) && !pte_huge(*pte));
return pte;
}