mm/migrate: add comment about permanent failure path

Let's add a comment about where the failed page goes to, which makes
code more readable.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Acked-by: Rafael Aquini <aquini@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/migrate.c b/mm/migrate.c
index f9e16350d09c4cf6d6c280587b4995d3102d5524..626ca3c5d07b874428047d9555d4fee5c3435d51 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1125,7 +1125,12 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
                                nr_succeeded++;
                                break;
                        default:
-                               /* Permanent failure */
+                               /*
+                                * Permanent failure (-EBUSY, -ENOSYS, etc.):
+                                * unlike -EAGAIN case, the failed page is
+                                * removed from migration page list and not
+                                * retried in the next outer loop.
+                                */
                                nr_failed++;
                                break;
                        }