[PATCH 11/14] mm: use SWP_SYNCHRONOUS_IO more intelligently

[Christoph Hellwig]

There is no point in trying to call bdev_read_page if SWP_SYNCHRONOUS_IO
is not set, as the device won't support it.  Also there is no point in
trying a bio submission if bdev_read_page failed.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 mm/page_io.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/page_io.c b/mm/page_io.c
index ccda7679008851..63b44b8221af0f 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -403,8 +403,11 @@ int swap_readpage(struct page *page, bool synchronous)
 		goto out;
 	}
 
-	ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
-	if (!ret) {
+	if (sis->flags & SWP_SYNCHRONOUS_IO) {
+		ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
+		if (ret)
+			goto out;
+
 		if (trylock_page(page)) {
 			swap_slot_free_notify(page);
 			unlock_page(page);
-- 
2.27.0