From: Mikulas Patocka mpatocka@redhat.com
commit 867de40c4c23e6d7f89f9ce4272a5d1b1484c122 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: 991bd8d7bc78 ("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 --- drivers/md/dm-writecache.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/drivers/md/dm-writecache.c +++ b/drivers/md/dm-writecache.c @@ -532,7 +532,11 @@ static void ssd_commit_superblock(struct
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;