From cc4f11e69fd00c61c38619759b07d00631bda5ca Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Fri, 28 Dec 2018 00:39:05 -0800
Subject: [PATCH] mm: migrate: lock buffers before migrate_page_move_mapping()
Git-commit: cc4f11e69fd00c61c38619759b07d00631bda5ca
Patch-mainline: v4.21-rc1
References: bsc#1084216
Lock buffers before calling into migrate_page_move_mapping() so that that
function doesn't have to know about buffers (which is somewhat unexpected
anyway) and all the buffer head logic is in buffer_migrate_page().
Link: http://lkml.kernel.org/r/20181211172143.7358-3-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Jan Kara <jack@suse.cz>
---
mm/migrate.c | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -743,24 +743,23 @@ int buffer_migrate_page(struct address_s
{
struct buffer_head *bh, *head;
int rc;
+ int expected_count;
if (!page_has_buffers(page))
return migrate_page(mapping, newpage, page, mode);
- head = page_buffers(page);
+ /* Check whether page does not have extra refs before we do more work */
+ expected_count = expected_page_refs(page);
+ if (page_count(page) != expected_count)
+ return -EAGAIN;
- rc = migrate_page_move_mapping(mapping, newpage, page, head, mode, 0);
+ head = page_buffers(page);
+ if (!buffer_migrate_lock_buffers(head, mode))
+ return -EAGAIN;
+ rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
if (rc != MIGRATEPAGE_SUCCESS)
- return rc;
-
- /*
- * In the async case, migrate_page_move_mapping locked the buffers
- * with an IRQ-safe spinlock held. In the sync case, the buffers
- * need to be locked now
- */
- if (mode != MIGRATE_ASYNC)
- BUG_ON(!buffer_migrate_lock_buffers(head, mode));
+ goto unlock_buffers;
ClearPagePrivate(page);
set_page_private(newpage, page_private(page));
@@ -782,6 +781,8 @@ int buffer_migrate_page(struct address_s
else
migrate_page_states(newpage, page);
+ rc = MIGRATEPAGE_SUCCESS;
+unlock_buffers:
bh = head;
do {
unlock_buffer(bh);
@@ -790,7 +791,7 @@ int buffer_migrate_page(struct address_s
} while (bh != head);
- return MIGRATEPAGE_SUCCESS;
+ return rc;
}
EXPORT_SYMBOL(buffer_migrate_page);
#endif