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block: mq-deadline: Fix dd_finish_request() for zoned devices

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commit 2820e5d082 upstream.

dd_finish_request() tests if the per prio fifo_list is not empty to
determine if request dispatching must be restarted for handling blocked
write requests to zoned devices with a call to
blk_mq_sched_mark_restart_hctx(). While simple, this implementation has
2 problems:

1) Only the priority level of the completed request is considered.
   However, writes to a zone may be blocked due to other writes to the
   same zone using a different priority level. While this is unlikely to
   happen in practice, as writing a zone with different IO priorirites
   does not make sense, nothing in the code prevents this from
   happening.
2) The use of list_empty() is dangerous as dd_finish_request() does not
   take dd->lock and may run concurrently with the insert and dispatch
   code.

Fix these 2 problems by testing the write fifo list of all priority
levels using the new helper dd_has_write_work(), and by testing each
fifo list using list_empty_careful().

Fixes: c807ab520f ("block/mq-deadline: Add I/O priority support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20221124021208.242541-2-damien.lemoal@opensource.wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Damien Le Moal 2022-11-24 11:12:07 +09:00 • committed by Justin Hammond
parent 541eb5836d
commit f2cac06528
1 changed files with 15 additions and 3 deletions
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18
block/mq-deadline.c
View file

@ -791,6 +791,18 @@ static void dd_prepare_request(struct request *rq)
rq->elv.priv[0] = NULL;
}
static bool dd_has_write_work(struct blk_mq_hw_ctx *hctx)
{
struct deadline_data *dd = hctx->queue->elevator->elevator_data;
enum dd_prio p;
for (p = 0; p <= DD_PRIO_MAX; p++)
if (!list_empty_careful(&dd->per_prio[p].fifo_list[DD_WRITE]))
return true;
return false;
}
/*
* Callback from inside blk_mq_free_request().
*
@ -813,7 +825,6 @@ static void dd_finish_request(struct request *rq)
struct deadline_data *dd = q->elevator->elevator_data;
const u8 ioprio_class = dd_rq_ioclass(rq);
const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
struct dd_per_prio *per_prio = &dd->per_prio[prio];
/*
* The block layer core may call dd_finish_request() without having
@ -829,9 +840,10 @@ static void dd_finish_request(struct request *rq)
spin_lock_irqsave(&dd->zone_lock, flags);
blk_req_zone_write_unlock(rq);
if (!list_empty(&per_prio->fifo_list[DD_WRITE]))
blk_mq_sched_mark_restart_hctx(rq->mq_hctx);
spin_unlock_irqrestore(&dd->zone_lock, flags);
if (dd_has_write_work(rq->mq_hctx))
blk_mq_sched_mark_restart_hctx(rq->mq_hctx);
}
}