Commit b2676e14 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
Browse files

dm writecache: count number of blocks written, not number of write bios 



Change dm-writecache, so that it counts the number of blocks written
instead of the number of write bios. Bios can be split and requeued
using the dm_accept_partial_bio function, so counting bios caused
inaccurate results.

Fixes: e3a35d03 ("dm writecache: add event counters")
Reported-by: default avatarYu Kuai <yukuai1@huaweicloud.com>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
parent 2c6e755b

Documentation/admin-guide/device-mapper/writecache.rst

+5 −5
Original line number Diff line number Diff line
@@ -82,11 +82,11 @@ Status: 
4. the number of blocks under writeback

5. the number of read blocks

6. the number of read blocks that hit the cache

7. the number of write requests

8. the number of write requests that hit uncommitted block

9. the number of write requests that hit committed block

10. the number of write requests that bypass the cache

11. the number of write requests that are allocated in the cache

7. the number of write blocks

8. the number of write blocks that hit uncommitted block

9. the number of write blocks that hit committed block

10. the number of write blocks that bypass the cache

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

drivers/md/dm-writecache.c

+9 −3
Original line number Diff line number Diff line
@@ -1413,6 +1413,9 @@ static void writecache_bio_copy_ssd(struct dm_writecache *wc, struct bio *bio, 
	bio->bi_iter.bi_sector = start_cache_sec;

	dm_accept_partial_bio(bio, bio_size >> SECTOR_SHIFT);



	wc->stats.writes += bio->bi_iter.bi_size >> wc->block_size_bits;

	wc->stats.writes_allocate += (bio->bi_iter.bi_size - wc->block_size) >> wc->block_size_bits;



	if (unlikely(wc->uncommitted_blocks >= wc->autocommit_blocks)) {

		wc->uncommitted_blocks = 0;

		queue_work(wc->writeback_wq, &wc->flush_work);
@@ -1428,9 +1431,10 @@ static enum wc_map_op writecache_map_write(struct dm_writecache *wc, struct bio 
	do {

		bool found_entry = false;

		bool search_used = false;

		wc->stats.writes++;

		if (writecache_has_error(wc))

		if (writecache_has_error(wc)) {

			wc->stats.writes += bio->bi_iter.bi_size >> wc->block_size_bits;

			return WC_MAP_ERROR;

		}

		e = writecache_find_entry(wc, bio->bi_iter.bi_sector, 0);

		if (e) {

			if (!writecache_entry_is_committed(wc, e)) {
@@ -1454,9 +1458,10 @@ static enum wc_map_op writecache_map_write(struct dm_writecache *wc, struct bio 
		if (unlikely(!e)) {

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

direct_write:

				wc->stats.writes_around++;

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

				writecache_map_remap_origin(wc, bio, e);

				wc->stats.writes_around += bio->bi_iter.bi_size >> wc->block_size_bits;

				wc->stats.writes += bio->bi_iter.bi_size >> wc->block_size_bits;

				return WC_MAP_REMAP_ORIGIN;

			}

			wc->stats.writes_blocked_on_freelist++;
@@ -1470,6 +1475,7 @@ static enum wc_map_op writecache_map_write(struct dm_writecache *wc, struct bio 
bio_copy:

		if (WC_MODE_PMEM(wc)) {

			bio_copy_block(wc, bio, memory_data(wc, e));

			wc->stats.writes++;

		} else {

			writecache_bio_copy_ssd(wc, bio, e, search_used);

			return WC_MAP_REMAP;