Patch "mm: soft-offline: fix num_poisoned_pages counting on concurrent events" has been added to the 4.0-stable tree

This is a note to let you know that I've just added the patch titled

    mm: soft-offline: fix num_poisoned_pages counting on concurrent events

to the 4.0-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mm-soft-offline-fix-num_poisoned_pages-counting-on-concurrent-events.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let [off-list ref] know about it.

From 602498f9aa43d4951eece3fd6ad95a6d0a78d537 Mon Sep 17 00:00:00 2001

From: Naoya Horiguchi <redacted>
Date: Tue, 5 May 2015 16:23:46 -0700
Subject: mm: soft-offline: fix num_poisoned_pages counting on concurrent events

From: Naoya Horiguchi <redacted>

commit 602498f9aa43d4951eece3fd6ad95a6d0a78d537 upstream.

If multiple soft offline events hit one free page/hugepage concurrently,
soft_offline_page() can handle the free page/hugepage multiple times,
which makes num_poisoned_pages counter increased more than once.  This
patch fixes this wrong counting by checking TestSetPageHWPoison for normal
papes and by checking the return value of dequeue_hwpoisoned_huge_page()
for hugepages.

Signed-off-by: Naoya Horiguchi <redacted>
Acked-by: Dean Nelson <redacted>
Cc: Andi Kleen <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 mm/memory-failure.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c

@@ -1721,12 +1721,12 @@ int soft_offline_page(struct page *page,
 	} else if (ret == 0) { /* for free pages */
 		if (PageHuge(page)) {
 			set_page_hwpoison_huge_page(hpage);
-			dequeue_hwpoisoned_huge_page(hpage);
-			atomic_long_add(1 << compound_order(hpage),
+			if (!dequeue_hwpoisoned_huge_page(hpage))
+				atomic_long_add(1 << compound_order(hpage),
 					&num_poisoned_pages);
 		} else {
-			SetPageHWPoison(page);
-			atomic_long_inc(&num_poisoned_pages);
+			if (!TestSetPageHWPoison(page))
+				atomic_long_inc(&num_poisoned_pages);
 		}
 	}
 	unset_migratetype_isolate(page, MIGRATE_MOVABLE);

Patches currently in stable-queue which might be from n-horiguchi@ah.jp.nec.com are

queue-4.0/mm-soft-offline-fix-num_poisoned_pages-counting-on-concurrent-events.patch
queue-4.0/mm-memory-failure-call-shake_page-when-error-hits-thp-tail-page.patch