On Tue, Nov 27, 2012 at 02:07:05PM +0000, Mel Gorman wrote:
> On Tue, Nov 27, 2012 at 09:23:59PM +0800, Hillf Danton wrote:
> > If we have to avoid migrating to a node that is nearly full, put page
> > and return zero.
> >
> > Signed-off-by: Hillf Danton <dhi...@gmail.com>
>
> Correct. In this series, the bug was actually introduced back in "mm:
> migrate: Introduce migrate_misplaced_page()" so I'm working the fix to
> be a fix on top of that patch and will ensure it gets carried through
> properly in the THP patch that happens at the end of the series. This will
> work out better in terms of bisection if the tree gets merged and allows
> a partial tree to be properly tested. Can I get your signed off on this
> patch please? This would be applied on top of "mm: migrate: Introduce
> migrate_misplaced_page()"
>
> Thanks.
>
After slotting the fix into the right place in the series and resolving
the conflict, the overall diff looks like;
diff --git a/mm/migrate.c b/mm/migrate.c
index b0c1585..ed0bdea 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1515,6 +1515,8 @@ bool numamigrate_update_ratelimit(pg_data_t *pgdat)
int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
{
+ int ret = 0;
+
/* Avoid migrating to a node that is nearly full */
if (migrate_balanced_pgdat(pgdat, 1)) {
int page_lru;
@@ -1524,13 +1526,8 @@ int numamigrate_isolate_page(pg_data_t *pgdat, struct
page *page)
return 0;
}
- /*
- * Page is isolated which takes a reference count so now the
- * callers reference can be safely dropped without the page
- * disappearing underneath us during migration
- */
- put_page(page);
-
+ /* Page is isolated */
+ ret = 1;
page_lru = page_is_file_cache(page);
if (!PageTransHuge(page))
inc_zone_page_state(page, NR_ISOLATED_ANON + page_lru);
@@ -1540,7 +1537,17 @@ int numamigrate_isolate_page(pg_data_t *pgdat, struct
page *page)
HPAGE_PMD_NR);
}
- return 1;
+ /*
+ * Page is either isolated or there is not enough space on the target
+ * node. If isolated, then it has taken a reference count and the
+ * callers reference can be safely dropped without the page
+ * disappearing underneath us during migration. Otherwise the page is
+ * not to be migrated but the callers reference should still be
+ * dropped so it does not leak.
+ */
+ put_page(page);
+
+ return ret;
}
/*
--
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