The patch titled
Subject: hugetlb: prevent BUG_ON in hugetlb_fault() -> hugetlb_cow()
has been added to the -mm tree. Its filename is
hugetlb-prevent-bug_on-in-hugetlb_fault-hugetlb_cow.patch
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------------------------------------------------------
From: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Subject: hugetlb: prevent BUG_ON in hugetlb_fault() -> hugetlb_cow()
66aebce747eaf ("hugetlb: fix race condition in hugetlb_fault()") added
code to avoid a race condition by elevating the page refcount in
hugetlb_fault() while calling hugetlb_cow().
However, one code path in hugetlb_cow() includes an assertion that the
page count is 1, whereas it may now also have the value 2 in this path.
The consensus is that this BUG_ON has served its purpose, so rather than
extending it to cover both cases, we just remove it.
Signed-off-by: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Acked-by: Mel Gorman <mel@xxxxxxxxx>
Acked-by: Hillf Danton <dhillf@xxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.0.29+, 3.2.16+, 3.3.3+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 1 -
1 file changed, 1 deletion(-)
diff -puN mm/hugetlb.c~hugetlb-prevent-bug_on-in-hugetlb_fault-hugetlb_cow mm/hugetlb.c
--- a/mm/hugetlb.c~hugetlb-prevent-bug_on-in-hugetlb_fault-hugetlb_cow
+++ a/mm/hugetlb.c
@@ -2499,7 +2499,6 @@ retry_avoidcopy:
if (outside_reserve) {
BUG_ON(huge_pte_none(pte));
if (unmap_ref_private(mm, vma, old_page, address)) {
- BUG_ON(page_count(old_page) != 1);
BUG_ON(huge_pte_none(pte));
spin_lock(&mm->page_table_lock);
ptep = huge_pte_offset(mm, address & huge_page_mask(h));
_
Subject: Subject: hugetlb: prevent BUG_ON in hugetlb_fault() -> hugetlb_cow()
Patches currently in -mm which might be from cmetcalf@xxxxxxxxxx are
linux-next.patch
hugetlb-prevent-bug_on-in-hugetlb_fault-hugetlb_cow.patch
list_debug-warn-for-adding-something-already-in-the-list.patch
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