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null_blk: guarantee device restart in all irq modes 

In single-queue (block layer) mode,the function null_rq_prep_fn stops
the device if alloc_cmd fails. Then, once stopped, the device must be
restarted on the next command completion, so that the request(s) for
which alloc_cmd failed can be requeued. Otherwise the device hangs.

Unfortunately, device restart is currently performed only for delayed
completions, i.e., in irqmode==2. This fact causes hangs, for the
above reasons, with the other irqmodes in combination with single-queue
block layer.

This commits addresses this issue by making sure that, if stopped, the
device is properly restarted for all irqmodes on completions.

Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Signed-off-by: Arianna AVanzini <avanzini@google.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Arianna Avanzini 2015-12-01 11:48:18 +01:00 committed by Jens Axboe
parent 3c395a969a
commit cf8ecc5a84
1 changed files with 17 additions and 14 deletions
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31
drivers/block/null_blk.c
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@ -217,6 +217,8 @@ static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq, int can_wait)
static void end_cmd(struct nullb_cmd *cmd)
{
struct request_queue *q = NULL;
switch (queue_mode) {
case NULL_Q_MQ:
blk_mq_end_request(cmd->rq, 0);
@ -227,27 +229,28 @@ static void end_cmd(struct nullb_cmd *cmd)
break;
case NULL_Q_BIO:
bio_endio(cmd->bio);
break;
goto free_cmd;
}
if (cmd->rq)
q = cmd->rq->q;
/* Restart queue if needed, as we are freeing a tag */
if (q && !q->mq_ops && blk_queue_stopped(q)) {
unsigned long flags;
spin_lock_irqsave(q->queue_lock, flags);
if (blk_queue_stopped(q))
blk_start_queue(q);
spin_unlock_irqrestore(q->queue_lock, flags);
}
free_cmd:
free_cmd(cmd);
}
static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer)
{
struct nullb_cmd *cmd = container_of(timer, struct nullb_cmd, timer);
struct request_queue *q = NULL;
if (cmd->rq)
q = cmd->rq->q;
if (q && !q->mq_ops && blk_queue_stopped(q)) {
spin_lock(q->queue_lock);
if (blk_queue_stopped(q))
blk_start_queue(q);
spin_unlock(q->queue_lock);
}
end_cmd(cmd);
end_cmd(container_of(timer, struct nullb_cmd, timer));
return HRTIMER_NORESTART;
}