The patch titled Subject: hugetlb: detect race upon page allocation failure during COW has been removed from the -mm tree. Its filename was hugetlb-detect-race-upon-page-allocation-failure-during-cow.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ From: Hillf Danton <dhillf@xxxxxxxxx> Subject: hugetlb: detect race upon page allocation failure during COW Currently we are not rechecking pte_same in hugetlb_cow after we take ptl lock again in the page allocation failure code path and simply retry again. This is not an issue at the moment because hugetlb fault path is protected by hugetlb_instantiation_mutex so we cannot race. The original page is locked and so we cannot race even with the page migration. Let's add the pte_same check anyway as we want to be consistent with the other check later in this function and be safe if we ever remove the mutex. [mhocko@xxxxxxx: reworded the changelog] Signed-off-by: Hillf Danton <dhillf@xxxxxxxxx> Signed-off-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 @@ -2408,7 +2408,14 @@ 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); } _ Patches currently in -mm which might be from dhillf@xxxxxxxxx are origin.patch linux-next.patch mm-hugetlb-undo-change-to-page-mapcount-in-fault-handler.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html