linux-kernel - [PATCH 10/13] mm: use SWP_SYNCHRONOUS

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Date:   Thu, 24 Sep 2020 08:51:37 +0200
From:   Christoph Hellwig <hch@....de>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Song Liu <song@...nel.org>, Hans de Goede <hdegoede@...hat.com>,
        Coly Li <colyli@...e.de>, Richard Weinberger <richard@....at>,
        Minchan Kim <minchan@...nel.org>,
        Johannes Thumshirn <Johannes.Thumshirn@....com>,
        Justin Sanders <justin@...aid.com>,
        linux-mtd@...ts.infradead.org, dm-devel@...hat.com,
        linux-block@...r.kernel.org, linux-bcache@...r.kernel.org,
        linux-kernel@...r.kernel.org, drbd-dev@...ts.linbit.com,
        linux-raid@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, cgroups@...r.kernel.org,
        Jan Kara <jack@...e.cz>,
        Johannes Thumshirn <johannes.thumshirn@....com>
Subject: [PATCH 10/13] mm: use SWP_SYNCHRONOUS_IO more intelligently

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.

Signed-off-by: Christoph Hellwig <hch@....de>
Reviewed-by: Jan Kara <jack@...e.cz>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@....com>
---
 mm/page_io.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/mm/page_io.c b/mm/page_io.c
index e485a6e8a6cddb..b199b87e0aa92b 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -403,15 +403,17 @@ int swap_readpage(struct page *page, bool synchronous)
 		goto out;
 	}
 
-	ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
-	if (!ret) {
-		if (trylock_page(page)) {
-			swap_slot_free_notify(page);
-			unlock_page(page);
-		}
+	if (sis->flags & SWP_SYNCHRONOUS_IO) {
+		ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
+		if (!ret) {
+			if (trylock_page(page)) {
+				swap_slot_free_notify(page);
+				unlock_page(page);
+			}
 
-		count_vm_event(PSWPIN);
-		goto out;
+			count_vm_event(PSWPIN);
+			goto out;
+		}
 	}
 
 	ret = 0;
-- 
2.28.0