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dm writecache: write at least 4k when committing

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commit 867de40c4c upstream.

SSDs perform badly with sub-4k writes (because they perfrorm
read-modify-write internally), so make sure writecache writes at least
4k when committing.

Fixes: 991bd8d7bc ("dm writecache: commit just one block, not a full page")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mikulas Patocka 2021-06-21 14:48:29 -04:00 • committed by Greg Kroah-Hartman
commit b716ccffbc
1 changed files with 5 additions and 1 deletions
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6
drivers/md/dm-writecache.c
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@ -532,7 +532,11 @@ static void ssd_commit_superblock(struct dm_writecache *wc)
region.bdev = wc->ssd_dev->bdev;
region.sector = 0;
region.count = wc->block_size >> SECTOR_SHIFT;
region.count = max(4096U, wc->block_size) >> SECTOR_SHIFT;
if (unlikely(region.sector + region.count > wc->metadata_sectors))
region.count = wc->metadata_sectors - region.sector;
region.sector += wc->start_sector;
req.bi_op = REQ_OP_WRITE;