[PATCH v3 05/14] block: Hold a reference on zone write plugs to schedule submission

Damien Le Moal
2024-05-01T11:09:15Z

Since a zone write plug BIO work is a field of struct blk_zone_wplug, we
must ensure that a zone write plug is never freed when its BIO
submission work is queued or running. Do this by holding a reference on
the zone write plug when the submission work is scheduled for execution
with queue_work() and releasing the reference at the end of the
execution of the work function blk_zone_wplug_bio_work().
The helper function disk_zone_wplug_schedule_bio_work() is introduced to
get a reference on a zone write plug and queue its work. This helper is
used in disk_zone_wplug_unplug_bio() and disk_zone_wplug_handle_error().

Fixes: dd291d77cc90 ("block: Introduce zone write plugging")
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
block/blk-zoned.c | 26 +++++++++++++++++++++-----
1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 23ad1de0da62..78557f810f1d 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -1132,6 +1132,19 @@ bool blk_zone_plug_bio(struct bio *bio, unsigned int nr_segs)
}
EXPORT_SYMBOL_GPL(blk_zone_plug_bio);

+static void disk_zone_wplug_schedule_bio_work(struct gendisk *disk,
+ struct blk_zone_wplug *zwplug)
+{
+ /*
+ * Take a reference on the zone write plug and schedule the submission
+ * of the next plugged BIO. blk_zone_wplug_bio_work() will release the
+ * reference we take here.
+ */
+ WARN_ON_ONCE(!(zwplug->flags & BLK_ZONE_WPLUG_PLUGGED));
+ atomic_inc(&zwplug->ref);
+ queue_work(disk->zone_wplugs_wq, &zwplug->bio_work);
+}
+
static void disk_zone_wplug_unplug_bio(struct gendisk *disk,
struct blk_zone_wplug *zwplug)
{
@@ -1151,8 +1164,8 @@ static void disk_zone_wplug_unplug_bio(struct gendisk *disk,

/* Schedule submission of the next plugged BIO if we have one. */
if (!bio_list_empty(&zwplug->bio_list)) {
+ disk_zone_wplug_schedule_bio_work(disk, zwplug);
spin_unlock_irqrestore(&zwplug->lock, flags);
- queue_work(disk->zone_wplugs_wq, &zwplug->bio_work);
return;
}

@@ -1252,14 +1265,14 @@ static void blk_zone_wplug_bio_work(struct work_struct *work)
if (!bio) {
zwplug->flags &= ~BLK_ZONE_WPLUG_PLUGGED;
spin_unlock_irqrestore(&zwplug->lock, flags);
- return;
+ goto put_zwplug;
}

if (!blk_zone_wplug_prepare_bio(zwplug, bio)) {
/* Error recovery will decide what to do with the BIO. */
bio_list_add_head(&zwplug->bio_list, bio);
spin_unlock_irqrestore(&zwplug->lock, flags);
- return;
+ goto put_zwplug;
}

spin_unlock_irqrestore(&zwplug->lock, flags);
@@ -1275,6 +1288,10 @@ static void blk_zone_wplug_bio_work(struct work_struct *work)
*/
if (bdev->bd_has_submit_bio)
blk_queue_exit(bdev->bd_disk->queue);
+
+put_zwplug:
+ /* Drop the reference we took in disk_zone_wplug_schedule_bio_work(). */
+ disk_put_zone_wplug(zwplug);
}

static unsigned int blk_zone_wp_offset(struct blk_zone *zone)
@@ -1354,8 +1371,7 @@ static void disk_zone_wplug_handle_error(struct gendisk *disk,

/* Restart BIO submission if we still have any BIO left. */
if (!bio_list_empty(&zwplug->bio_list)) {
- WARN_ON_ONCE(!(zwplug->flags & BLK_ZONE_WPLUG_PLUGGED));
- queue_work(disk->zone_wplugs_wq, &zwplug->bio_work);
+ disk_zone_wplug_schedule_bio_work(disk, zwplug);
goto unlock;
}

--
2.44.0