linux-kernel - [PATCH AUTOSEL 5.12 091/160] dm writecache: commit just one block, not a full page

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Date:   Tue,  6 Jul 2021 07:17:17 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Mikulas Patocka <mpatocka@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Sasha Levin <sashal@...nel.org>, dm-devel@...hat.com
Subject: [PATCH AUTOSEL 5.12 091/160] dm writecache: commit just one block, not a full page

From: Mikulas Patocka <mpatocka@...hat.com>

[ Upstream commit 991bd8d7bc78966b4dc427b53a144f276bffcd52 ]

Some architectures have pages larger than 4k and committing a full
page causes needless overhead.

Fix this by writing a single block when committing the superblock.

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/md/dm-writecache.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index 7bb4d83e90cc..51b26db56ba9 100644
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -532,11 +532,7 @@ static void ssd_commit_superblock(struct dm_writecache *wc)
 
 	region.bdev = wc->ssd_dev->bdev;
 	region.sector = 0;
-	region.count = PAGE_SIZE >> SECTOR_SHIFT;
-
-	if (unlikely(region.sector + region.count > wc->metadata_sectors))
-		region.count = wc->metadata_sectors - region.sector;
-
+	region.count = wc->block_size >> SECTOR_SHIFT;
 	region.sector += wc->start_sector;
 
 	req.bi_op = REQ_OP_WRITE;
-- 
2.30.2