linux-kernel - Re: [PATCH v2 4/6] scsi: pm8001: Use sas_task_find

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Date:   Tue, 4 Oct 2022 06:51:35 +0200
From:   Jinpu Wang <jinpu.wang@...os.com>
To:     John Garry <john.garry@...wei.com>
Cc:     damien.lemoal@....com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, hare@...e.de,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxarm@...wei.com, ipylypiv@...gle.com, changyuanl@...gle.com,
        hch@....de, yanaijie@...wei.com
Subject: Re: [PATCH v2 4/6] scsi: pm8001: Use sas_task_find_rq() for tagging

On Fri, Sep 30, 2022 at 1:05 PM John Garry <john.garry@...wei.com> wrote:
>
> On 30/09/2022 11:20, John Garry wrote:
> > BTW, I do notice that we still have this global lock in delivery path
> > which should be removed at some stage:
> > > int mvs_queue_command(struct sas_task *task, gfp_t gfp_flags)
> > {
> >      ...
> >
> >      spin_lock_irqsave(&mvi->lock, flags);
> >      rc = mvs_task_prep(task, mvi, is_tmf, tmf, &pass);
> >      ...
> >      spin_unlock_irqrestore(&mvi->lock, flags);
> > }
> >
>
> oops... that's mvsas. But pm8001 does still use a big lock (which we
> should get rid off):
Yes, would be great to get rid of the per ha lock.
>
> int pm8001_queue_command(struct sas_task *task, gfp_t gfp_flags)
> {
>         ...
>         pm8001_dbg(pm8001_ha, IO, "pm8001_task_exec device\n");
>
>         spin_lock_irqsave(&pm8001_ha->lock, flags);
>
>
> Thanks,
> John
>
> > That really will affect performance...
>