[PATCH 1/2] mm/migrate.c: Fix return code when migration fails

[Alistair Popple <apopple@nvidia.com>]

When a page fails to migrate move_pages() returns the error code in a
per-page array of status values. The function call itself is also
supposed to return a summary error code indicating that a failure
occurred.

This doesn't always happen. Instead success can be returned even
though some pages failed to migrate. This is due to incorrectly
returning the error code from store_status() rather than the code from
add_page_for_migration. Fix this by only returning an error from
store_status() if the store actually failed.

Signed-off-by: Alistair Popple <apopple@nvidia.com>
Fixes: a49bd4d71637 ("mm, numa: rework do_pages_move")
---
 mm/migrate.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 24baad2571e3..bb3a37245e13 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2222,7 +2222,9 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
 		 * If the page is already on the target node (!err), store the
 		 * node, otherwise, store the err.
 		 */
-		err = store_status(status, i, err ? : current_node, 1);
+		err1 = store_status(status, i, err ? : current_node, 1);
+		if (err1)
+			err = err1;
 		if (err)
 			goto out_flush;
 
-- 
2.39.2