From: Dan Williams <dan.j.williams@intel.com>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
Hans Verkuil <hans.verkuil@cisco.com>,
Alexandre Belloni <alexandre.belloni@free-electrons.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Dave Jiang <dave.jiang@intel.com>,
Vishal L Verma <vishal.l.verma@intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-nvdimm <linux-nvdimm@lists.01.org>
Subject: Re: [PATCH 1/3] cdev: Finish the cdev api with queued mode support
Date: Wed, 20 Jan 2021 12:38:27 -0800 [thread overview]
Message-ID: <CAPcyv4j8nfFT5=0T5U7rpNnD29XpTaAmNU5fkaA1--CrmWfRUw@mail.gmail.com> (raw)
In-Reply-To: <809823fb-6eb6-8ce9-c49a-d85b03897fc7@deltatee.com>
On Wed, Jan 20, 2021 at 11:51 AM Logan Gunthorpe <logang@deltatee.com> wrote:
>
>
>
>
> On 2021-01-20 12:38 p.m., Dan Williams wrote:
> > ...common reference count handling scenarios were addressed, but the
> > shutdown-synchronization problem was only mentioned as something driver
> > developers need to be aware in the following note:
> >
> > NOTE: This guarantees that associated sysfs callbacks are not running
> > or runnable, however any cdevs already open will remain and their fops
> > will still be callable even after this function returns.
> >
> > Remove that responsibility from driver developers with the concept of a
> > 'queued' mode for cdevs.
>
> I find the queued name confusing. What's being queued?
Yeah, as I mentioned to Christoph, a bit too much inspiration from
q_usage_count. Perhaps "managed" makes more sense.
>
> > +static const struct file_operations cdev_queued_fops = {
> > + .owner = THIS_MODULE,
> > + .open = cdev_queued_open,
> > + .unlocked_ioctl = cdev_queued_ioctl,
> > + .compat_ioctl = compat_ptr_ioctl,
> > + .llseek = noop_llseek,
> > +};
>
> Why do we only protect these fops? I'd find it a bit confusing to have
> ioctl protected from use after del, but not write/read/etc.
More ops can certainly be added over time, I didn't want to go do the
work to wrap all file_operations before getting consensus on the idea
that the cdev core should provide managed ops at all.
The other question I'm posing with cdev_operations is whether the cdev
core should take away some of the flexibility from end drivers in
favor of adding more type safety. For example, mandate that all ioctls
take a pointer argument not an integer argument? The question of
whether wrapping cdev file_operations around a new cdev_operations is
a good idea can be deferred after finalizing a mechanism for managed
cdev file_operations.
next prev parent reply other threads:[~2021-01-20 20:44 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-20 19:38 [PATCH 0/3] cdev: Generic shutdown handling Dan Williams
2021-01-20 19:38 ` [PATCH 1/3] cdev: Finish the cdev api with queued mode support Dan Williams
2021-01-20 19:46 ` Christoph Hellwig
2021-01-20 20:20 ` Dan Williams
2021-01-20 21:39 ` Dan Williams
2021-01-20 19:50 ` Logan Gunthorpe
2021-01-20 20:38 ` Dan Williams [this message]
2021-01-21 8:13 ` Greg KH
2021-01-21 17:50 ` Dan Williams
2021-01-20 19:39 ` [PATCH 2/3] libnvdimm/ida: Switch to non-deprecated ida helpers Dan Williams
2021-01-20 19:39 ` [PATCH 3/3] libnvdimm/ioctl: Switch to cdev_register_queued() Dan Williams
2021-01-21 8:15 ` Greg KH
2021-01-21 17:02 ` Dan Williams
2021-01-30 1:59 ` [PATCH 0/3] cdev: Generic shutdown handling Dan Williams
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAPcyv4j8nfFT5=0T5U7rpNnD29XpTaAmNU5fkaA1--CrmWfRUw@mail.gmail.com' \
--to=dan.j.williams@intel.com \
--cc=alexandre.belloni@free-electrons.com \
--cc=dave.jiang@intel.com \
--cc=gregkh@linuxfoundation.org \
--cc=hans.verkuil@cisco.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-nvdimm@lists.01.org \
--cc=logang@deltatee.com \
--cc=viro@zeniv.linux.org.uk \
--cc=vishal.l.verma@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).