Patch "mm/hwpoison: fix wrong num_poisoned_pages accounting" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    mm/hwpoison: fix wrong num_poisoned_pages accounting

to the 4.4-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-hwpoison-fix-wrong-num_poisoned_pages-accounting.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From d7e69488bd04de165667f6bc741c1c0ec6042ab9 Mon Sep 17 00:00:00 2001
From: Minchan Kim <minchan@kernel.org>
Date: Thu, 28 Apr 2016 16:18:44 -0700
Subject: mm/hwpoison: fix wrong num_poisoned_pages accounting

From: Minchan Kim <minchan@kernel.org>

commit d7e69488bd04de165667f6bc741c1c0ec6042ab9 upstream.

Currently, migration code increses num_poisoned_pages on *failed*
migration page as well as successfully migrated one at the trial of
memory-failure.  It will make the stat wrong.  As well, it marks the
page as PG_HWPoison even if the migration trial failed.  It would mean
we cannot recover the corrupted page using memory-failure facility.

This patches fixes it.

Signed-off-by: Minchan Kim <minchan@kernel.org>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
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/migrate.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -963,7 +963,13 @@ out:
 		dec_zone_page_state(page, NR_ISOLATED_ANON +
 				page_is_file_cache(page));
 		/* Soft-offlined page shouldn't go through lru cache list */
-		if (reason == MR_MEMORY_FAILURE) {
+		if (reason == MR_MEMORY_FAILURE && rc == MIGRATEPAGE_SUCCESS) {
+			/*
+			 * With this release, we free successfully migrated
+			 * page and set PG_HWPoison on just freed page
+			 * intentionally. Although it's rather weird, it's how
+			 * HWPoison flag works at the moment.
+			 */
 			put_page(page);
 			if (!test_set_page_hwpoison(page))
 				num_poisoned_pages_inc();


Patches currently in stable-queue which might be from minchan@kernel.org are

queue-4.4/mm-vmscan-reclaim-highmem-zone-if-buffer_heads-is-over-limit.patch
queue-4.4/mm-hwpoison-fix-wrong-num_poisoned_pages-accounting.patch