From 2ee73ef60db4d79b9f9b8cd501e8188b5179449f Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Mon, 11 Jul 2022 16:31:52 -0400
Subject: [PATCH] dm writecache: count number of blocks discarded, not number
 of discard bios
Git-commit: 2ee73ef60db4d79b9f9b8cd501e8188b5179449f
Patch-mainline: v6.0-rc1
References: jsc#PED-2765

Change dm-writecache, so that it counts the number of blocks discarded
instead of the number of discard bios. Make it consistent with the
read and write statistics counters that were changed to count the
number of blocks instead of bios.

Fixes: e3a35d03407c ("dm writecache: add event counters")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Coly Li <colyli@suse.de>

---
 Documentation/admin-guide/device-mapper/writecache.rst | 2 +-
 drivers/md/dm-writecache.c                             | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/device-mapper/writecache.rst b/Documentation/admin-guide/device-mapper/writecache.rst
index 0772d2160f9c..60c16b7fd5ac 100644
--- a/Documentation/admin-guide/device-mapper/writecache.rst
+++ b/Documentation/admin-guide/device-mapper/writecache.rst
@@ -89,7 +89,7 @@ Status:
 11. the number of write blocks that are allocated in the cache
 12. the number of write requests that are blocked on the freelist
 13. the number of flush requests
-14. the number of discard requests
+14. the number of discarded blocks
 
 Messages:
 	flush
diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index 6282c77abe7b..ead008ea38f2 100644
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -1514,7 +1514,7 @@ static enum wc_map_op writecache_map_flush(struct dm_writecache *wc, struct bio
 
 static enum wc_map_op writecache_map_discard(struct dm_writecache *wc, struct bio *bio)
 {
-	wc->stats.discards++;
+	wc->stats.discards += bio->bi_iter.bi_size >> wc->block_size_bits;
 
 	if (writecache_has_error(wc))
 		return WC_MAP_ERROR;
-- 
2.35.3