[PATCH v5 1/5] mm,page_alloc: Bail out earlier on -ENOMEM in alloc_contig_migrate_range

[Oscar Salvador]

Currently, __alloc_contig_migrate_range can generate -EINTR, -ENOMEM or -EBUSY,
and report them down the chain.
The problem is that when migrate_pages() reports -ENOMEM, we keep going till we
exhaust all the try-attempts (5 at the moment) instead of bailing out.

migrate_pages() bails out right away on -ENOMEM because it is considered a fatal
error. Do the same here instead of keep going and retrying.

Signed-off-by: Oscar Salvador <osalva...@suse.de>
Acked-by: Vlastimil Babka <vba...@suse.cz>
Reviewed-by: David Hildenbrand <da...@redhat.com>
---
 mm/page_alloc.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cfc72873961d..a4f67063b85f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8481,7 +8481,7 @@ static int __alloc_contig_migrate_range(struct 
compact_control *cc,
                        }
                        tries = 0;
                } else if (++tries == 5) {
-                       ret = ret < 0 ? ret : -EBUSY;
+                       ret = -EBUSY;
                        break;
                }
 
@@ -8491,6 +8491,12 @@ static int __alloc_contig_migrate_range(struct 
compact_control *cc,
 
                ret = migrate_pages(&cc->migratepages, alloc_migration_target,
                                NULL, (unsigned long)&mtc, cc->mode, 
MR_CONTIG_RANGE);
+               /*
+                * On -ENOMEM, migrate_pages() bails out right away. It is 
pointless
+                * to retry again over this error, so do the same here.
+                */
+               if (ret == -ENOMEM)
+                       break;
        }
        if (ret < 0) {
                putback_movable_pages(&cc->migratepages);
-- 
2.16.3