linux-kernel - [PATCH 4/4] dm-writecache: count the number of blocks discarded, not the number of discard bios

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Date:   Mon, 11 Jul 2022 16:31:52 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@...hat.com>
To:     Yu Kuai <yukuai1@...weicloud.com>,
        Mike Snitzer <msnitzer@...hat.com>
cc:     agk@...hat.com, dm-devel@...hat.com, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yi.zhang@...wei.com
Subject: [PATCH 4/4] dm-writecache: count the number of blocks discarded,
 not the number of discard bios

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.

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

Index: linux-2.6/drivers/md/dm-writecache.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-writecache.c
+++ linux-2.6/drivers/md/dm-writecache.c
@@ -1514,7 +1514,7 @@ static enum wc_map_op writecache_map_flu
 
 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;
Index: linux-2.6/Documentation/admin-guide/device-mapper/writecache.rst
===================================================================
--- linux-2.6.orig/Documentation/admin-guide/device-mapper/writecache.rst
+++ linux-2.6/Documentation/admin-guide/device-mapper/writecache.rst
@@ -87,7 +87,7 @@ 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