[PATCH 3.13.y-ckt 051/122] mm/memory-failure: call shake_page() when error hits thp tail page

From: Kamal Mostafa
Date: Wed Jun 17 2015 - 18:30:42 EST

3.13.11-ckt22 -stable review patch. If anyone has any objections, please let me know.


From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>

commit 09789e5de18e4e442870b2d700831f5cb802eb05 upstream.

Currently memory_failure() calls shake_page() to sweep pages out from
pcplists only when the victim page is 4kB LRU page or thp head page.
But we should do this for a thp tail page too.

Consider that a memory error hits a thp tail page whose head page is on
a pcplist when memory_failure() runs. Then, the current kernel skips
shake_pages() part, so hwpoison_user_mappings() returns without calling
split_huge_page() nor try_to_unmap() because PageLRU of the thp head is
still cleared due to the skip of shake_page().

As a result, me_huge_page() runs for the thp, which is broken behavior.

One effect is a leak of the thp. And another is to fail to isolate the
memory error, so later access to the error address causes another MCE,
which kills the processes which used the thp.

This patch fixes this problem by calling shake_page() for thp tail case.

Fixes: 385de35722c9 ("thp: allow a hwpoisoned head page to be put back to LRU")
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Acked-by: Dean Nelson <dnelson@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Hidetoshi Seto <seto.hidetoshi@xxxxxxxxxxxxxx>
Cc: Jin Dongming <jin.dongming@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
mm/memory-failure.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 112be59f..95ebdc0 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1149,10 +1149,10 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
* The check (unnecessarily) ignores LRU pages being isolated and
* walked by the page reclaim code, however that's not a big loss.
- if (!PageHuge(p) && !PageTransTail(p)) {
- if (!PageLRU(p))
- shake_page(p, 0);
- if (!PageLRU(p)) {
+ if (!PageHuge(p)) {
+ if (!PageLRU(hpage))
+ shake_page(hpage, 0);
+ if (!PageLRU(hpage)) {
* shake_page could have turned it free.

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