dm writecache: flush origin device when writing and cache is full

stable inclusion
from stable-5.10.51
commit 1b5918b087b1dd7bf193340f25ca63c50a277638
bugzilla: 175263 https://gitee.com/openeuler/kernel/issues/I4DT6F

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1b5918b087b1dd7bf193340f25ca63c50a277638

--------------------------------

commit ee55b92a upstream.

Commit d53f1faf ("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: NMikulas Patocka <mpatocka@redhat.com>
Fixes: d53f1faf ("dm writecache: do direct write if the cache is full")
Cc: stable@vger.kernel.org # v5.7+
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

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) {
@@ -2483,7 +2487,7 @@ 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;