linux-kernel - Re: [PATCH v9 3/6] iommufd: Add iommufd_access_change

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Date:   Thu, 27 Jul 2023 11:47:32 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     <kevin.tian@...el.com>, <yi.l.liu@...el.com>, <joro@...tes.org>,
        <will@...nel.org>, <robin.murphy@....com>,
        <alex.williamson@...hat.com>, <shuah@...nel.org>,
        <linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>,
        <kvm@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
        <mjrosato@...ux.ibm.com>, <farman@...ux.ibm.com>
Subject: Re: [PATCH v9 3/6] iommufd: Add iommufd_access_change_ioas helper

On Thu, Jul 27, 2023 at 11:40:17AM -0300, Jason Gunthorpe wrote:
> On Thu, Jul 27, 2023 at 12:23:08AM -0700, Nicolin Chen wrote:

> > +	if (new_ioas) {
> > +		rc = iopt_add_access(&new_ioas->iopt, access);
> > +		if (rc) {
> > +			iommufd_put_object(&new_ioas->obj);
> > +			access->ioas = cur_ioas;
> > +			return rc;
> > +		}
> > +		iommufd_ref_to_users(&new_ioas->obj);
> 
> Kevin's suggestion to just open code the refcount_inc here

Will replace this iommufd_ref_to_users with a refcount_inc in v10.

> And have a wrapper func that does:
> 
> iommufd_access_change_ioas_id(struct iommufd_access *access, u32 id)
> {
> 	struct iommufd_ioas *ioas = iommufd_get_ioas(ictx, ioas_id);
> 	int rc;
> 
> 	if (IS_ERR(ioas))
> 		return PTR_ERR(ioas);
> 	rc = iommufd_access_change_ioas(access, ioas);
> 	iommufd_put_object(&ioas->obj);
> 	return rc;
> }
> 
> Does looks cleaner

I see. So we can drop iommufd_put_object(&new_ioas->obj) in
iommufd_access_change_ioas().

> Then we delete iommufd_ref_to_users() as there are no users (once all
> the branches are merged).

Ack.

Nicolin