Commit e7fad909 authored by Dmitry Fomichev's avatar Dmitry Fomichev Committed by Mike Snitzer
Browse files

dm zoned: reduce overhead of backing device checks 



Commit 75d66ffb added backing device health checks and as a part
of these checks, check_events() block ops template call is invoked in
dm-zoned mapping path as well as in reclaim and flush path. Calling
check_events() with ATA or SCSI backing devices introduces a blocking
scsi_test_unit_ready() call being made in sd_check_events(). Even though
the overhead of calling scsi_test_unit_ready() is small for ATA zoned
devices, it is much larger for SCSI and it affects performance in a very
negative way.

Fix this performance regression by executing check_events() only in case
of any I/O errors. The function dmz_bdev_is_dying() is modified to call
only blk_queue_dying(), while calls to check_events() are made in a new
helper function, dmz_check_bdev().

Reported-by: default avatarzhangxiaoxu <zhangxiaoxu5@huawei.com>
Fixes: 75d66ffb ("dm zoned: properly handle backing device failure")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarDmitry Fomichev <dmitry.fomichev@wdc.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 72d7df4c

drivers/md/dm-zoned-metadata.c

+19 −10
Original line number Diff line number Diff line
@@ -554,6 +554,7 @@ static struct dmz_mblock *dmz_get_mblock(struct dmz_metadata *zmd, 
		       TASK_UNINTERRUPTIBLE);

	if (test_bit(DMZ_META_ERROR, &mblk->state)) {

		dmz_release_mblock(zmd, mblk);

		dmz_check_bdev(zmd->dev);

		return ERR_PTR(-EIO);

	}
@@ -625,6 +626,8 @@ static int dmz_rdwr_block(struct dmz_metadata *zmd, int op, sector_t block, 
	ret = submit_bio_wait(bio);

	bio_put(bio);



	if (ret)

		dmz_check_bdev(zmd->dev);

	return ret;

}
@@ -691,6 +694,7 @@ static int dmz_write_dirty_mblocks(struct dmz_metadata *zmd, 
			       TASK_UNINTERRUPTIBLE);

		if (test_bit(DMZ_META_ERROR, &mblk->state)) {

			clear_bit(DMZ_META_ERROR, &mblk->state);

			dmz_check_bdev(zmd->dev);

			ret = -EIO;

		}

		nr_mblks_submitted--;
@@ -768,7 +772,7 @@ int dmz_flush_metadata(struct dmz_metadata *zmd) 
	/* If there are no dirty metadata blocks, just flush the device cache */

	if (list_empty(&write_list)) {

		ret = blkdev_issue_flush(zmd->dev->bdev, GFP_NOIO, NULL);

		goto out;

		goto err;

	}



	/*
@@ -778,7 +782,7 @@ int dmz_flush_metadata(struct dmz_metadata *zmd) 
	 */

	ret = dmz_log_dirty_mblocks(zmd, &write_list);

	if (ret)

		goto out;

		goto err;



	/*

	 * The log is on disk. It is now safe to update in place
@@ -786,11 +790,11 @@ int dmz_flush_metadata(struct dmz_metadata *zmd) 
	 */

	ret = dmz_write_dirty_mblocks(zmd, &write_list, zmd->mblk_primary);

	if (ret)

		goto out;

		goto err;



	ret = dmz_write_sb(zmd, zmd->mblk_primary);

	if (ret)

		goto out;

		goto err;



	while (!list_empty(&write_list)) {

		mblk = list_first_entry(&write_list, struct dmz_mblock, link);
@@ -805,16 +809,20 @@ int dmz_flush_metadata(struct dmz_metadata *zmd) 


	zmd->sb_gen++;

out:

	if (ret && !list_empty(&write_list)) {

		spin_lock(&zmd->mblk_lock);

		list_splice(&write_list, &zmd->mblk_dirty_list);

		spin_unlock(&zmd->mblk_lock);

	}



	dmz_unlock_flush(zmd);

	up_write(&zmd->mblk_sem);



	return ret;



err:

	if (!list_empty(&write_list)) {

		spin_lock(&zmd->mblk_lock);

		list_splice(&write_list, &zmd->mblk_dirty_list);

		spin_unlock(&zmd->mblk_lock);

	}

	if (!dmz_check_bdev(zmd->dev))

		ret = -EIO;

	goto out;

}



/*
@@ -1244,6 +1252,7 @@ static int dmz_update_zone(struct dmz_metadata *zmd, struct dm_zone *zone) 
	if (ret) {

		dmz_dev_err(zmd->dev, "Get zone %u report failed",

			    dmz_id(zmd, zone));

		dmz_check_bdev(zmd->dev);

		return ret;

	}

drivers/md/dm-zoned-reclaim.c

+2 −6
Original line number Diff line number Diff line
@@ -82,6 +82,7 @@ static int dmz_reclaim_align_wp(struct dmz_reclaim *zrc, struct dm_zone *zone, 
			    "Align zone %u wp %llu to %llu (wp+%u) blocks failed %d",

			    dmz_id(zmd, zone), (unsigned long long)wp_block,

			    (unsigned long long)block, nr_blocks, ret);

		dmz_check_bdev(zrc->dev);

		return ret;

	}
@@ -489,12 +490,7 @@ static void dmz_reclaim_work(struct work_struct *work) 
	ret = dmz_do_reclaim(zrc);

	if (ret) {

		dmz_dev_debug(zrc->dev, "Reclaim error %d\n", ret);

		if (ret == -EIO)

			/*

			 * LLD might be performing some error handling sequence

			 * at the underlying device. To not interfere, do not

			 * attempt to schedule the next reclaim run immediately.

			 */

		if (!dmz_check_bdev(zrc->dev))

			return;

	}

drivers/md/dm-zoned-target.c

+38 −16
Original line number Diff line number Diff line
@@ -80,6 +80,8 @@ static inline void dmz_bio_endio(struct bio *bio, blk_status_t status) 


	if (status != BLK_STS_OK && bio->bi_status == BLK_STS_OK)

		bio->bi_status = status;

	if (bio->bi_status != BLK_STS_OK)

		bioctx->target->dev->flags |= DMZ_CHECK_BDEV;



	if (refcount_dec_and_test(&bioctx->ref)) {

		struct dm_zone *zone = bioctx->zone;
@@ -565,29 +567,49 @@ out: 
}



/*

 * Check the backing device availability. If it's on the way out,

 * Check if the backing device is being removed. If it's on the way out,

 * start failing I/O. Reclaim and metadata components also call this

 * function to cleanly abort operation in the event of such failure.

 */

bool dmz_bdev_is_dying(struct dmz_dev *dmz_dev)

{

	struct gendisk *disk;

	if (dmz_dev->flags & DMZ_BDEV_DYING)

		return true;



	if (dmz_dev->flags & DMZ_CHECK_BDEV)

		return !dmz_check_bdev(dmz_dev);



	if (!(dmz_dev->flags & DMZ_BDEV_DYING)) {

		disk = dmz_dev->bdev->bd_disk;

	if (blk_queue_dying(bdev_get_queue(dmz_dev->bdev))) {

		dmz_dev_warn(dmz_dev, "Backing device queue dying");

		dmz_dev->flags |= DMZ_BDEV_DYING;

		} else if (disk->fops->check_events) {

			if (disk->fops->check_events(disk, 0) &

					DISK_EVENT_MEDIA_CHANGE) {

				dmz_dev_warn(dmz_dev, "Backing device offline");

				dmz_dev->flags |= DMZ_BDEV_DYING;

	}



	return dmz_dev->flags & DMZ_BDEV_DYING;

}



/*

 * Check the backing device availability. This detects such events as

 * backing device going offline due to errors, media removals, etc.

 * This check is less efficient than dmz_bdev_is_dying() and should

 * only be performed as a part of error handling.

 */

bool dmz_check_bdev(struct dmz_dev *dmz_dev)

{

	struct gendisk *disk;



	dmz_dev->flags &= ~DMZ_CHECK_BDEV;



	if (dmz_bdev_is_dying(dmz_dev))

		return false;



	disk = dmz_dev->bdev->bd_disk;

	if (disk->fops->check_events &&

	    disk->fops->check_events(disk, 0) & DISK_EVENT_MEDIA_CHANGE) {

		dmz_dev_warn(dmz_dev, "Backing device offline");

		dmz_dev->flags |= DMZ_BDEV_DYING;

	}



	return dmz_dev->flags & DMZ_BDEV_DYING;

	return !(dmz_dev->flags & DMZ_BDEV_DYING);

}



/*
@@ -902,8 +924,8 @@ static int dmz_prepare_ioctl(struct dm_target *ti, struct block_device **bdev) 
{

	struct dmz_target *dmz = ti->private;



	if (dmz_bdev_is_dying(dmz->dev))

		return -ENODEV;

	if (!dmz_check_bdev(dmz->dev))

		return -EIO;



	*bdev = dmz->dev->bdev;

drivers/md/dm-zoned.h

+2 −0
Original line number Diff line number Diff line
@@ -72,6 +72,7 @@ struct dmz_dev { 


/* Device flags. */

#define DMZ_BDEV_DYING		(1 << 0)

#define DMZ_CHECK_BDEV		(2 << 0)



/*

 * Zone descriptor.
@@ -255,5 +256,6 @@ void dmz_schedule_reclaim(struct dmz_reclaim *zrc); 
 * Functions defined in dm-zoned-target.c

 */

bool dmz_bdev_is_dying(struct dmz_dev *dmz_dev);

bool dmz_check_bdev(struct dmz_dev *dmz_dev);



#endif /* DM_ZONED_H */

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