The patch titled
Subject: hugetlb: detect race upon page allocation failure during COW
has been added to the -mm tree. Its filename is
hugetlb-detect-race-upon-page-allocation-failure-during-cow.patch
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------------------------------------------------------
From: Hillf Danton <dhillf@xxxxxxxxx>
Subject: hugetlb: detect race upon page allocation failure during COW
In the error path where we failed to allocate a new huge page, we should
check whether a racing thread has added this page for us while this thread
waited for the page_table_lock.
We are serialized by hugetlb_instantiation_mutex on the pagefault patch
but this race can occur when another thread is performing page migration.
Signed-off-by: Hillf Danton <dhillf@xxxxxxxxx>
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Johannes Weiner <jweiner@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff -puN mm/hugetlb.c~hugetlb-detect-race-upon-page-allocation-failure-during-cow mm/hugetlb.c
--- a/mm/hugetlb.c~hugetlb-detect-race-upon-page-allocation-failure-during-cow
+++ a/mm/hugetlb.c
@@ -2407,7 +2407,14 @@ retry_avoidcopy:
BUG_ON(page_count(old_page) != 1);
BUG_ON(huge_pte_none(pte));
spin_lock(&mm->page_table_lock);
- goto retry_avoidcopy;
+ ptep = huge_pte_offset(mm, address & huge_page_mask(h));
+ if (likely(pte_same(huge_ptep_get(ptep), pte)))
+ goto retry_avoidcopy;
+ /*
+ * race occurs while re-acquiring page_table_lock, and
+ * our job is done.
+ */
+ return 0;
}
WARN_ON_ONCE(1);
}
_
Subject: Subject: hugetlb: detect race upon page allocation failure during COW
Patches currently in -mm which might be from dhillf@xxxxxxxxx are
origin.patch
linux-next.patch
hugetlb-detect-race-upon-page-allocation-failure-during-cow.patch
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