linux-kernel - Re: [PATCH v2 2/3] iommufd/device: Make hwpt_list list

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Date:   Mon, 30 Jan 2023 11:03:09 -0800
From:   Nicolin Chen <nicolinc@...dia.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     <kevin.tian@...el.com>, <yi.l.liu@...el.com>,
        <iommu@...ts.linux.dev>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] iommufd/device: Make hwpt_list list_add/del
 symmetric

On Mon, Jan 30, 2023 at 10:59:32AM -0400, Jason Gunthorpe wrote:
> On Sat, Jan 28, 2023 at 01:18:10PM -0800, Nicolin Chen wrote:
> > Since the list_del() of hwpt_item is done in iommufd_device_detach(), move
> > its list_add_tail() to a similar place in iommufd_device_do_attach().
> > 
> > Also move and place the mutex outside the iommufd_device_auto_get_domain()
> > and iommufd_device_do_attach() calls, to serialize attach/detach routines.
> > This adds an additional locking protection so that the following patch can
> > safely remove devices_lock.
> 
> That should be two patches then, this is just moving one line of code
> from what I can tell?

The mutex is used to protect the list. So moving the list means
we'd need to the mutex too. What this patch does is to enlarge
the protection scope a bit to cover iommufd_device_do_attach()
and iommufd_device_auto_get_domain().

I can revise a bit of the commit message to mention this.

Thanks
Nicolin