From: Mikulas Patocka <mpatocka@redhat.com>

Date: Tue, 15 Jun 2021 13:45:55 -0400

Subject: [PATCH] dm writecache: flush origin device when writing and cache is

 full

Git-commit: ee55b92a7391bf871939330f662651b54be51b73

Patch-mainline: v5.14-rc1

References: git-fixes

Commit d53f1fafec9d086f1c5166436abefdaef30e0363 ("dm writecache: do

direct write if the cache is full") changed dm-writecache, so that it

writes directly to the origin device if the cache is full.

Unfortunately, it doesn't forward flush requests to the origin device,

so that there is a bug where flushes are being ignored.

Fix this by adding missing flush forwarding.

For PMEM mode, we fix this bug by disabling direct writes to the origin

device, because it performs better.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Fixes: d53f1fafec9d ("dm writecache: do direct write if the cache is full")

Cc: stable@vger.kernel.org # v5.7+

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

Acked-by: Hannes Reinecke <hare@suse.com>

---

 drivers/md/dm-writecache.c | 8 ++++++--

 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c

index 28bb6890fcf4..ddd368e0491d 100644

--- a/drivers/md/dm-writecache.c

+++ b/drivers/md/dm-writecache.c

@@ -1297,8 +1297,12 @@ static int writecache_map(struct dm_target *ti, struct bio *bio)

 			writecache_flush(wc);

 			if (writecache_has_error(wc))

 				goto unlock_error;

+			if (unlikely(wc->cleaner))

+				goto unlock_remap_origin;

 			goto unlock_submit;

 		} else {

+			if (dm_bio_get_target_bio_nr(bio))

+				goto unlock_remap_origin;

 			writecache_offload_bio(wc, bio);

 			goto unlock_return;

 		}

@@ -1377,7 +1381,7 @@ static int writecache_map(struct dm_target *ti, struct bio *bio)

 			}

 			e = writecache_pop_from_freelist(wc, (sector_t)-1);

 			if (unlikely(!e)) {

-				if (!found_entry) {

+				if (!WC_MODE_PMEM(wc) && !found_entry) {

 direct_write:

 					e = writecache_find_entry(wc, bio->bi_iter.bi_sector, WFE_RETURN_FOLLOWING);

 					if (e) {

@@ -2484,7 +2488,7 @@ static int writecache_ctr(struct dm_target *ti, unsigned argc, char **argv)

 		goto bad;

 	}

-	ti->num_flush_bios = 1;

+	ti->num_flush_bios = WC_MODE_PMEM(wc) ? 1 : 2;

 	ti->flush_supported = true;

 	ti->num_discard_bios = 1;

-- 

2.29.2