Commit 526d1006 authored by Li Nan's avatar Li Nan Committed by Mike Snitzer
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dm: support turning off block-core's io stats accounting 



Commit bc58ba94 ("block: add sysfs file for controlling io stats
accounting") allowed users to turn off disk stat accounting completely
by checking if queue flag QUEUE_FLAG_IO_STAT is set. In dm, this flag
is neither set nor checked: so block-core's io stats are continuously
counted and cannot be turned off.

Add support for turning off block-core's io stats accounting for dm.
Set QUEUE_FLAG_IO_STAT for dm's request_queue. If QUEUE_FLAG_IO_STAT
is set when an io starts, record the need for block core's io stats by
setting the DM_IO_BLK_STAT dm_io flag to avoid io stats being disabled
in the middle of the io.

DM statistics (dm-stats) is independent of block-core's io stats and
remains unchanged.

Signed-off-by: default avatarLi Nan <linan122@huawei.com>
Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
parent e118029c

drivers/md/dm-core.h

+2 −1
Original line number Diff line number Diff line
@@ -306,7 +306,8 @@ struct dm_io { 
 */

enum {

	DM_IO_ACCOUNTED,

	DM_IO_WAS_SPLIT

	DM_IO_WAS_SPLIT,

	DM_IO_BLK_STAT

};



static inline bool dm_io_flagged(struct dm_io *io, unsigned int bit)

drivers/md/dm.c

+11 −5
Original line number Diff line number Diff line
@@ -511,11 +511,14 @@ static void dm_io_acct(struct dm_io *io, bool end) 
	else

		sectors = io->sectors;



	if (dm_io_flagged(io, DM_IO_BLK_STAT)) {

		if (!end)

		bdev_start_io_acct(bio->bi_bdev, bio_op(bio), start_time);

	else

		bdev_end_io_acct(bio->bi_bdev, bio_op(bio), sectors,

			bdev_start_io_acct(bio->bi_bdev, bio_op(bio),

					   start_time);

		else

			bdev_end_io_acct(bio->bi_bdev, bio_op(bio),

					 sectors, start_time);

	}



	if (static_branch_unlikely(&stats_enabled) &&

	    unlikely(dm_stats_used(&md->stats))) {
@@ -592,6 +595,8 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio) 
	spin_lock_init(&io->lock);

	io->start_time = jiffies;

	io->flags = 0;

	if (blk_queue_io_stat(md->queue))

		dm_io_set_flag(io, DM_IO_BLK_STAT);



	if (static_branch_unlikely(&stats_enabled))

		dm_stats_record_start(&md->stats, &io->stats_aux);
@@ -2341,6 +2346,7 @@ int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t) 
		break;

	case DM_TYPE_BIO_BASED:

	case DM_TYPE_DAX_BIO_BASED:

		blk_queue_flag_set(QUEUE_FLAG_IO_STAT, md->queue);

		break;

	case DM_TYPE_NONE:

		WARN_ON_ONCE(true);