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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Mikulas Patocka <mpatocka@redhat.com>,
        Mike Snitzer <snitzer@redhat.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.12 086/242] dm writecache: commit just one block, not a full page
Date:   Thu, 15 Jul 2021 20:37:28 +0200
Message-Id: <20210715182608.164155579@linuxfoundation.org>
In-Reply-To: <20210715182551.731989182@linuxfoundation.org>
References: <20210715182551.731989182@linuxfoundation.org>
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From: Mikulas Patocka <mpatocka@redhat.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@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.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