mm: make generic_writepages() use plugging

This recovers a performance regression caused by the removal
of the per-device plugging.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index cc0ede169e41..24b7ac2bc36b 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1039,11 +1039,17 @@ static int __writepage(struct page *page, struct writeback_control *wbc,
 int generic_writepages(struct address_space *mapping,
                        struct writeback_control *wbc)
 {
+        struct blk_plug plug;
+        int ret;
+
         /* deal with chardevs and other special file */
         if (!mapping->a_ops->writepage)
                 return 0;
 
-        return write_cache_pages(mapping, wbc, __writepage, mapping);
+        blk_start_plug(&plug);
+        ret = write_cache_pages(mapping, wbc, __writepage, mapping);
+        blk_finish_plug(&plug);
+        return ret;
 }
 
 EXPORT_SYMBOL(generic_writepages);