linux-kernel - Re: [RFC PATCH 2/3] pci/doe: Use devm_xa

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Date:   Fri, 8 Jul 2022 07:45:12 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     Dan Williams <dan.j.williams@...el.com>,
        Matthew Wilcox <willy@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        <linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
        <linux-pci@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>
Subject: Re: [RFC PATCH 2/3] pci/doe: Use devm_xa_init()

On Thu, Jul 07, 2022 at 11:06:46AM -0500, Bjorn Helgaas wrote:
> On Tue, Jul 05, 2022 at 04:21:58PM -0700, ira.weiny@...el.com wrote:
> > From: Ira Weiny <ira.weiny@...el.com>
> > 
> > The XArray being used to store the protocols does not even store
> > allocated objects.
> 
> I guess the point is that the doe_mb->prots XArray doesn't reference
> any other objects that would need to be freed when destroying
> doe_mb->prots?

Yes.

> A few more words here would make the commit log more
> useful to non-XArray experts.

I'll update this to be more clear in a V1 if it goes that far.  But to clarify
here; the protocol information is a u16 vendor id and u8 protocol number.  So
we are able to store that in the unsigned long value that would normally be a
pointer to something in the XArray.

> 
> s|pci/doe|PCI/DOE| in subject to match the drivers/pci convention.

Yes. Sorry,

Thanks for the review,
Ira

> 
> > Use devm_xa_init() to automatically destroy the XArray when the PCI
> > device goes away.
> > 
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> > ---
> >  drivers/pci/doe.c | 14 ++------------
> >  1 file changed, 2 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> > index 0b02f33ef994..aa36f459d375 100644
> > --- a/drivers/pci/doe.c
> > +++ b/drivers/pci/doe.c
> > @@ -386,13 +386,6 @@ static int pci_doe_cache_protocols(struct pci_doe_mb *doe_mb)
> >  	return 0;
> >  }
> >  
> > -static void pci_doe_xa_destroy(void *mb)
> > -{
> > -	struct pci_doe_mb *doe_mb = mb;
> > -
> > -	xa_destroy(&doe_mb->prots);
> > -}
> > -
> >  static void pci_doe_destroy_workqueue(void *mb)
> >  {
> >  	struct pci_doe_mb *doe_mb = mb;
> > @@ -440,11 +433,8 @@ struct pci_doe_mb *pcim_doe_create_mb(struct pci_dev *pdev, u16 cap_offset)
> >  	doe_mb->pdev = pdev;
> >  	doe_mb->cap_offset = cap_offset;
> >  	init_waitqueue_head(&doe_mb->wq);
> > -
> > -	xa_init(&doe_mb->prots);
> > -	rc = devm_add_action(dev, pci_doe_xa_destroy, doe_mb);
> > -	if (rc)
> > -		return ERR_PTR(rc);
> > +	if (devm_xa_init(dev, &doe_mb->prots))
> > +		return ERR_PTR(-ENOMEM);
> >  
> >  	doe_mb->work_queue = alloc_ordered_workqueue("DOE: [%x]", 0,
> >  						     doe_mb->cap_offset);
> > -- 
> > 2.35.3
> >