Subject: + mm-memory-failurec-move-refcount-only-in-mf_count_increased.patch 
added to -mm tree
To: 
[email protected],[email protected],[email protected],[email protected],[email protected]
From: [email protected]
Date: Fri, 07 Feb 2014 13:44:56 -0800


The patch titled
     Subject: mm/memory-failure.c: move refcount only in !MF_COUNT_INCREASED
has been added to the -mm tree.  Its filename is
     mm-memory-failurec-move-refcount-only-in-mf_count_increased.patch

This patch should soon appear at
    
http://ozlabs.org/~akpm/mmots/broken-out/mm-memory-failurec-move-refcount-only-in-mf_count_increased.patch
and later at
    
http://ozlabs.org/~akpm/mmotm/broken-out/mm-memory-failurec-move-refcount-only-in-mf_count_increased.patch

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------------------------------------------------------
From: Naoya Horiguchi <[email protected]>
Subject: mm/memory-failure.c: move refcount only in !MF_COUNT_INCREASED

mce-test detected a test failure when injecting error to a thp tail page. 
This is because we take page refcount of the tail page in
madvise_hwpoison() while the fix in commit a3e0f9e47d5e
("mm/memory-failure.c: transfer page count from head page to tail page
after split thp") assumes that we always take refcount on the head page.

When a real memory error happens we take refcount on the head page where
memory_failure() is called without MF_COUNT_INCREASED set, so it seems to
me that testing memory error on thp tail page using madvise makes little
sense.

This patch cancels moving refcount in !MF_COUNT_INCREASED for valid testing.

Signed-off-by: Naoya Horiguchi <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Chen Gong <[email protected]>
Cc: <[email protected]>    [3.9+: a3e0f9e47d5e]
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/memory-failure.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff -puN 
mm/memory-failure.c~mm-memory-failurec-move-refcount-only-in-mf_count_increased 
mm/memory-failure.c
--- 
a/mm/memory-failure.c~mm-memory-failurec-move-refcount-only-in-mf_count_increased
+++ a/mm/memory-failure.c
@@ -945,8 +945,10 @@ static int hwpoison_user_mappings(struct
                         * to it. Similarly, page lock is shifted.
                         */
                        if (hpage != p) {
-                               put_page(hpage);
-                               get_page(p);
+                               if (!(flags && MF_COUNT_INCREASED)) {
+                                       put_page(hpage);
+                                       get_page(p);
+                               }
                                lock_page(p);
                                unlock_page(hpage);
                                *hpagep = p;
_

Patches currently in -mm which might be from [email protected] are

mm-memory-failurec-move-refcount-only-in-mf_count_increased.patch
mm-memory-failurec-move-refcount-only-in-mf_count_increased-fix.patch
mm-hugetlb-unify-region-structure-handling.patch
mm-hugetlb-improve-cleanup-resv_map-parameters.patch
mm-hugetlb-fix-race-in-region-tracking.patch
mm-hugetlb-remove-resv_map_put.patch
mm-hugetlb-use-vma_resv_map-map-types.patch
mm-hugetlb-improve-page-fault-scalability.patch
mm-hugetlb-improve-page-fault-scalability-fix.patch

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