[patch -mm 1/2] mm/compaction: split freepages without holding the zone lock fix

From: David Rientjes
Date: Tue Jun 21 2016 - 17:48:37 EST


If __isolate_free_page() fails, avoid adding to freelist so we don't call
map_pages() with it.

Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
Fix for mm-compaction-split-freepages-without-holding-the-zone-lock.patch in
-mm.

mm/compaction.c | 29 +++++++++++++----------------
1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -494,24 +494,21 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,

/* Found a free page, will break it into order-0 pages */
order = page_order(page);
- isolated = __isolate_free_page(page, page_order(page));
+ isolated = __isolate_free_page(page, order);
+ if (!isolated)
+ goto isolate_fail;
set_page_private(page, order);
total_isolated += isolated;
list_add_tail(&page->lru, freelist);
-
- /* If a page was split, advance to the end of it */
- if (isolated) {
- cc->nr_freepages += isolated;
- if (!strict &&
- cc->nr_migratepages <= cc->nr_freepages) {
- blockpfn += isolated;
- break;
- }
-
- blockpfn += isolated - 1;
- cursor += isolated - 1;
- continue;
+ cc->nr_freepages += isolated;
+ if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
+ blockpfn += isolated;
+ break;
}
+ /* Advance to end of split page */
+ blockpfn += isolated - 1;
+ cursor += isolated - 1;
+ continue;

isolate_fail:
if (strict)
@@ -622,7 +619,7 @@ isolate_freepages_range(struct compact_control *cc,
*/
}

- /* split_free_page does not map the pages */
+ /* __isolate_free_page() does not map the pages */
map_pages(&freelist);

if (pfn < end_pfn) {
@@ -1124,7 +1121,7 @@ static void isolate_freepages(struct compact_control *cc)
}
}

- /* split_free_page does not map the pages */
+ /* __isolate_free_page() does not map the pages */
map_pages(freelist);

/*