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block: Fix reference counting for zone write plugs in error state

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When zone is reset or finished, disk_zone_wplug_set_wp_offset() is
called to update the zone write plug write pointer offset and to clear
the zone error state (BLK_ZONE_WPLUG_ERROR flag) if it is set.
However, this processing is missing dropping the reference to the zone
write plug that was taken in disk_zone_wplug_set_error() when the error
flag was first set. Furthermore, the error state handling must release
the zone write plug lock to first execute a report zones command. When
the report zone races with a reset or finish operation that clears the
error, we can end up decrementing the zone write plug reference count
twice: once in disk_zone_wplug_set_wp_offset() for the reset/finish
operation and one more time in disk_zone_wplugs_work() once
disk_zone_wplug_handle_error() completes.

Fix this by introducing disk_zone_wplug_clear_error() as the symmetric
function of disk_zone_wplug_set_error(). disk_zone_wplug_clear_error()
decrements the zone write plug reference count obtained in
disk_zone_wplug_set_error() only if the error handling has not started
yet, that is, only if disk_zone_wplugs_work() has not yet taken the zone
write plug off the error list. This ensure that either
disk_zone_wplug_clear_error() or disk_zone_wplugs_work() drop the zone
write plug reference count.

Fixes: dd291d77cc ("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>
Link: https://lore.kernel.org/r/20240501110907.96950-5-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Damien Le Moal 2024-05-01 20:08:57 +09:00 committed by Jens Axboe
parent 74b7ae5f48
commit 19aad274c2
1 changed files with 49 additions and 26 deletions
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75
block/blk-zoned.c
View File

@ -658,6 +658,54 @@ static void disk_zone_wplug_abort_unaligned(struct gendisk *disk,
bio_list_merge(&zwplug->bio_list, &bl);
}
static inline void disk_zone_wplug_set_error(struct gendisk *disk,
struct blk_zone_wplug *zwplug)
{
unsigned long flags;
if (zwplug->flags & BLK_ZONE_WPLUG_ERROR)
return;
/*
* At this point, we already have a reference on the zone write plug.
* However, since we are going to add the plug to the disk zone write
* plugs work list, increase its reference count. This reference will
* be dropped in disk_zone_wplugs_work() once the error state is
* handled, or in disk_zone_wplug_clear_error() if the zone is reset or
* finished.
*/
zwplug->flags |= BLK_ZONE_WPLUG_ERROR;
atomic_inc(&zwplug->ref);
spin_lock_irqsave(&disk->zone_wplugs_lock, flags);
list_add_tail(&zwplug->link, &disk->zone_wplugs_err_list);
spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
}
static inline void disk_zone_wplug_clear_error(struct gendisk *disk,
struct blk_zone_wplug *zwplug)
{
unsigned long flags;
if (!(zwplug->flags & BLK_ZONE_WPLUG_ERROR))
return;
/*
* We are racing with the error handling work which drops the reference
* on the zone write plug after handling the error state. So remove the
* plug from the error list and drop its reference count only if the
* error handling has not yet started, that is, if the zone write plug
* is still listed.
*/
spin_lock_irqsave(&disk->zone_wplugs_lock, flags);
if (!list_empty(&zwplug->link)) {
list_del_init(&zwplug->link);
zwplug->flags &= ~BLK_ZONE_WPLUG_ERROR;
disk_put_zone_wplug(zwplug);
}
spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
}
/*
* Set a zone write plug write pointer offset to either 0 (zone reset case)
* or to the zone size (zone finish case). This aborts all plugged BIOs, which
@ -691,12 +739,7 @@ static void disk_zone_wplug_set_wp_offset(struct gendisk *disk,
* in a good state. So clear the error flag and decrement the
* error count if we were in error state.
*/
if (zwplug->flags & BLK_ZONE_WPLUG_ERROR) {
zwplug->flags &= ~BLK_ZONE_WPLUG_ERROR;
spin_lock(&disk->zone_wplugs_lock);
list_del_init(&zwplug->link);
spin_unlock(&disk->zone_wplugs_lock);
}
disk_zone_wplug_clear_error(disk, zwplug);
/*
* The zone write plug now has no BIO plugged: remove it from the
@ -885,26 +928,6 @@ void blk_zone_write_plug_attempt_merge(struct request *req)
spin_unlock_irqrestore(&zwplug->lock, flags);
}
static inline void disk_zone_wplug_set_error(struct gendisk *disk,
struct blk_zone_wplug *zwplug)
{
if (!(zwplug->flags & BLK_ZONE_WPLUG_ERROR)) {
unsigned long flags;
/*
* Increase the plug reference count. The reference will be
* dropped in disk_zone_wplugs_work() once the error state
* is handled.
*/
zwplug->flags |= BLK_ZONE_WPLUG_ERROR;
atomic_inc(&zwplug->ref);
spin_lock_irqsave(&disk->zone_wplugs_lock, flags);
list_add_tail(&zwplug->link, &disk->zone_wplugs_err_list);
spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
}
}
/*
* Check and prepare a BIO for submission by incrementing the write pointer
* offset of its zone write plug and changing zone append operations into