[dm-devel] [PATCH] dm-zoned: reduce overhead of backing device checks
Dmitry Fomichev
dmitry.fomichev at wdc.com
Wed Nov 6 22:34:35 UTC 2019
Commit 75d66ffb48efb3 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.
This commit fixes 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().
Cc: stable at vger.kernel.org
Fixes: 75d66ffb48efb3 ("dm zoned: properly handle backing device failure")
Signed-off-by: Dmitry Fomichev <dmitry.fomichev at wdc.com>
---
drivers/md/dm-zoned-metadata.c | 29 +++++++++++-------
drivers/md/dm-zoned-reclaim.c | 8 ++---
drivers/md/dm-zoned-target.c | 54 ++++++++++++++++++++++++----------
drivers/md/dm-zoned.h | 2 ++
4 files changed, 61 insertions(+), 32 deletions(-)
diff --git a/drivers/md/dm-zoned-metadata.c b/drivers/md/dm-zoned-metadata.c
index 595a73110e17..ac1179ca80d9 100644
--- a/drivers/md/dm-zoned-metadata.c
+++ b/drivers/md/dm-zoned-metadata.c
@@ -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;
}
diff --git a/drivers/md/dm-zoned-reclaim.c b/drivers/md/dm-zoned-reclaim.c
index d240d7ca8a8a..e7ace908a9b7 100644
--- a/drivers/md/dm-zoned-reclaim.c
+++ b/drivers/md/dm-zoned-reclaim.c
@@ -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;
}
diff --git a/drivers/md/dm-zoned-target.c b/drivers/md/dm-zoned-target.c
index 09f5a63e0803..e0b809bb4885 100644
--- a/drivers/md/dm-zoned-target.c
+++ b/drivers/md/dm-zoned-target.c
@@ -85,6 +85,8 @@ 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;
@@ -570,31 +572,51 @@ static int dmz_queue_chunk_work(struct dmz_target *dmz, struct bio *bio)
}
/*
- * 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_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;
- }
- }
+ if (dmz_dev->flags & DMZ_CHECK_BDEV)
+ return !dmz_check_bdev(dmz_dev);
+
+ 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;
}
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);
+}
+
/*
* Process a new BIO.
*/
@@ -907,8 +929,8 @@ 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;
diff --git a/drivers/md/dm-zoned.h b/drivers/md/dm-zoned.h
index d8e70b0ade35..5b5e493d479c 100644
--- a/drivers/md/dm-zoned.h
+++ b/drivers/md/dm-zoned.h
@@ -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 */
--
2.21.0
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