mm/hwpoison: fix wrong num_poisoned_pages accounting

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>

diff --git a/mm/migrate.c b/mm/migrate.c
index 6d17e0ab42d40f3253df41bbecc1e0d85acb204b..bbeb0b71fcf41b99a0173ba8dbb5990190fb59ce 100644 (file)
--- 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();