Commit 2b1c6d7a authored by Mikulas Patocka's avatar Mikulas Patocka
Browse files

dm: optimize REQ_PREFLUSH with data when using the linear target 



If the table has only linear targets and there is just one underlying
device, we can optimize REQ_PREFLUSH with data - we don't have to split
it to two bios - a flush and a write. We can pass it to the linear target
directly.

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Tested-by: default avatarBart Van Assche <bvanassche@acm.org>
Reviewed-by: default avatarBart Van Assche <bvanassche@acm.org>
parent 4466dd3d

drivers/md/dm-core.h

+1 −0
Original line number Diff line number Diff line
@@ -292,6 +292,7 @@ struct dm_io { 
	struct dm_io *next;

	struct dm_stats_aux stats_aux;

	blk_status_t status;

	bool requeue_flush_with_data;

	atomic_t io_count;

	struct mapped_device *md;

drivers/md/dm.c

+24 −8
Original line number Diff line number Diff line
@@ -490,18 +490,13 @@ u64 dm_start_time_ns_from_clone(struct bio *bio) 
}

EXPORT_SYMBOL_GPL(dm_start_time_ns_from_clone);



static inline bool bio_is_flush_with_data(struct bio *bio)

{

	return ((bio->bi_opf & REQ_PREFLUSH) && bio->bi_iter.bi_size);

}



static inline unsigned int dm_io_sectors(struct dm_io *io, struct bio *bio)

{

	/*

	 * If REQ_PREFLUSH set, don't account payload, it will be

	 * submitted (and accounted) after this flush completes.

	 */

	if (bio_is_flush_with_data(bio))

	if (io->requeue_flush_with_data)

		return 0;

	if (unlikely(dm_io_flagged(io, DM_IO_WAS_SPLIT)))

		return io->sectors;
@@ -590,6 +585,7 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio, gfp_t g 
	io = container_of(tio, struct dm_io, tio);

	io->magic = DM_IO_MAGIC;

	io->status = BLK_STS_OK;

	io->requeue_flush_with_data = false;



	/* one ref is for submission, the other is for completion */

	atomic_set(&io->io_count, 2);
@@ -948,6 +944,7 @@ static void __dm_io_complete(struct dm_io *io, bool first_stage) 
	struct mapped_device *md = io->md;

	blk_status_t io_error;

	bool requeued;

	bool requeue_flush_with_data;



	requeued = dm_handle_requeue(io, first_stage);

	if (requeued && first_stage)
@@ -964,6 +961,7 @@ static void __dm_io_complete(struct dm_io *io, bool first_stage) 
		__dm_start_io_acct(io);

		dm_end_io_acct(io);

	}

	requeue_flush_with_data = io->requeue_flush_with_data;

	free_io(io);

	smp_wmb();

	this_cpu_dec(*md->pending_io);
@@ -976,7 +974,7 @@ static void __dm_io_complete(struct dm_io *io, bool first_stage) 
	if (requeued)

		return;



	if (bio_is_flush_with_data(bio)) {

	if (unlikely(requeue_flush_with_data)) {

		/*

		 * Preflush done for flush with data, reissue

		 * without REQ_PREFLUSH.
@@ -1996,12 +1994,30 @@ static void dm_split_and_process_bio(struct mapped_device *md, 
	}

	init_clone_info(&ci, io, map, bio, is_abnormal);



	if (bio->bi_opf & REQ_PREFLUSH) {

	if (unlikely((bio->bi_opf & REQ_PREFLUSH) != 0)) {

		/*

		 * The "flush_bypasses_map" is set on targets where it is safe

		 * to skip the map function and submit bios directly to the

		 * underlying block devices - currently, it is set for dm-linear

		 * and dm-stripe.

		 *

		 * If we have just one underlying device (i.e. there is one

		 * linear target or multiple linear targets pointing to the same

		 * device), we can send the flush with data directly to it.

		 */

		if (map->flush_bypasses_map) {

			struct list_head *devices = dm_table_get_devices(map);

			if (devices->next == devices->prev)

				goto send_preflush_with_data;

		}

		if (bio->bi_iter.bi_size)

			io->requeue_flush_with_data = true;

		__send_empty_flush(&ci);

		/* dm_io_complete submits any data associated with flush */

		goto out;

	}



send_preflush_with_data:

	if (static_branch_unlikely(&zoned_enabled) &&

	    (bio_op(bio) == REQ_OP_ZONE_RESET_ALL)) {

		error = __send_zone_reset_all(&ci);