The patch titled
Subject: mm, page_alloc: keep pcp count and list contents in sync if struct page is corrupted
has been added to the -mm tree. Its filename is
mm-page_alloc-keep-pcp-count-and-list-contents-in-sync-if-struct-page-is-corrupted.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-keep-pcp-count-and-list-contents-in-sync-if-struct-page-is-corrupted.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-keep-pcp-count-and-list-contents-in-sync-if-struct-page-is-corrupted.patch
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From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: mm, page_alloc: keep pcp count and list contents in sync if struct page is corrupted
Vlastimil Babka pointed out that 479f854a207c ("mm, page_alloc: defer
debugging checks of pages allocated from the PCP") will allow the per-cpu
list counter to be out of sync with the per-cpu list contents if a struct
page is corrupted.
The consequence is an infinite loop if the per-cpu lists get fully drained
by free_pcppages_bulk because all the lists are empty but the count is
positive. The infinite loop occurs here
do {
batch_free++;
if (++migratetype == MIGRATE_PCPTYPES)
migratetype = 0;
list = &pcp->lists[migratetype];
} while (list_empty(list));
What the user sees is a bad page warning followed by a soft lockup with
interrupts disabled in free_pcppages_bulk().
This patch keeps the accounting in sync.
Fixes: 479f854a207c ("mm, page_alloc: defer debugging checks of pages allocated from the PCP")
Link: http://lkml.kernel.org/r/20161202112951.23346-2-mgorman@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [4.7+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff -puN mm/page_alloc.c~mm-page_alloc-keep-pcp-count-and-list-contents-in-sync-if-struct-page-is-corrupted mm/page_alloc.c
--- a/mm/page_alloc.c~mm-page_alloc-keep-pcp-count-and-list-contents-in-sync-if-struct-page-is-corrupted
+++ a/mm/page_alloc.c
@@ -2218,7 +2218,7 @@ static int rmqueue_bulk(struct zone *zon
unsigned long count, struct list_head *list,
int migratetype, bool cold)
{
- int i;
+ int i, alloced = 0;
spin_lock(&zone->lock);
for (i = 0; i < count; ++i) {
@@ -2243,13 +2243,21 @@ static int rmqueue_bulk(struct zone *zon
else
list_add_tail(&page->lru, list);
list = &page->lru;
+ alloced++;
if (is_migrate_cma(get_pcppage_migratetype(page)))
__mod_zone_page_state(zone, NR_FREE_CMA_PAGES,
-(1 << order));
}
+
+ /*
+ * i pages were removed from the buddy list even if some leak due
+ * to check_pcp_refill failing so adjust NR_FREE_PAGES based
+ * on i. Do not confuse with 'alloced' which is the number of
+ * pages added to the pcp list.
+ */
__mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
spin_unlock(&zone->lock);
- return i;
+ return alloced;
}
#ifdef CONFIG_NUMA
_
Patches currently in -mm which might be from mgorman@xxxxxxxxxxxxxxxxxxx are
mm-page_alloc-keep-pcp-count-and-list-contents-in-sync-if-struct-page-is-corrupted.patch
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