Re: [PATCH 2/4] scsi: remove an extra queue reference

Ming Lei
2022-10-19T01:23:39Z

On Wed, Oct 19, 2022 at 09:16:57AM +0800, Ming Lei wrote:
> On Tue, Oct 18, 2022 at 03:57:18PM +0200, Christoph Hellwig wrote:
> > Now that blk_mq_destroy_queue does not release the queue reference, there
> > is no need for a second queue reference to be held by the scsi_device.
> >
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > ---
> > drivers/scsi/scsi_scan.c | 1 -
> > drivers/scsi/scsi_sysfs.c | 1 -
> > 2 files changed, 2 deletions(-)
> >
> > diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> > index 5d27f5196de6f..0a95fa787fdf4 100644
> > --- a/drivers/scsi/scsi_scan.c
> > +++ b/drivers/scsi/scsi_scan.c
> > @@ -344,7 +344,6 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
> > sdev->request_queue = q;
> > q->queuedata = sdev;
> > __scsi_init_queue(sdev->host, q);
> > - WARN_ON_ONCE(!blk_get_queue(q));
> >
> > depth = sdev->host->cmd_per_lun ?: 1;
> >
> > diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> > index 1214c6f07bc64..c95177ca6ed26 100644
> > --- a/drivers/scsi/scsi_sysfs.c
> > +++ b/drivers/scsi/scsi_sysfs.c
> > @@ -1478,7 +1478,6 @@ void __scsi_remove_device(struct scsi_device *sdev)
> > mutex_unlock(&sdev->state_mutex);
> >
> > blk_mq_destroy_queue(sdev->request_queue);
> > - blk_put_queue(sdev->request_queue);
>
> The above put is counter-pair of blk_get_queue() in scsi_alloc_sdev, and
> the original blk_put_queue() in blk_mq_destroy_queue() is counter-pair of
> the initial get in blk_alloc_queue().
>
> Now blk_put_queue() is moved out of blk_mq_destroy_queue(), I am wondering
> how the scsi queue lifetime can work correctly with this patch? Or is there
> bug in current scsi code?

oops, the above blk_put_queue() is actually added in the 1st patch, so
this patch is fine, sorry for the noise.

thanks,
Ming