This is a note to let you know that I've just added the patch titled dm writecache: write at least 4k when committing to the 5.12-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: dm-writecache-write-at-least-4k-when-committing.patch and it can be found in the queue-5.12 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 867de40c4c23e6d7f89f9ce4272a5d1b1484c122 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka <mpatocka@xxxxxxxxxx> Date: Mon, 21 Jun 2021 14:48:29 -0400 Subject: dm writecache: write at least 4k when committing From: Mikulas Patocka <mpatocka@xxxxxxxxxx> 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@xxxxxxxxxx> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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; Patches currently in stable-queue which might be from mpatocka@xxxxxxxxxx are queue-5.12/dm-writecache-don-t-split-bios-when-overwriting-cont.patch queue-5.12/dm-writecache-write-at-least-4k-when-committing.patch queue-5.12/dm-writecache-commit-just-one-block-not-a-full-page.patch queue-5.12/dm-writecache-flush-origin-device-when-writing-and-cache-is-full.patch