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From: Ray Strode <rstrode@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Howells <dhowells@redhat.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Steven Whitehouse <swhiteho@redhat.com>,
	Nicolas Dichtel <nicolas.dichtel@6wind.com>,
	raven@themaw.net, keyrings@vger.kernel.org,
	linux-usb@vger.kernel.org,
	linux-block <linux-block@vger.kernel.org>,
	Christian Brauner <christian@brauner.io>,
	LSM List <linux-security-module@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	"Ray, Debarshi" <debarshi.ray@gmail.com>,
	Robbie Harwood <rharwood@redhat.com>
Subject: Re: Why add the general notification queue and its sources
Date: Thu, 5 Sep 2019 14:32:40 -0400
Message-ID: <CAKCoTu7ms_Mr-q08d9XB3uascpzwBa5LF9JTT2aq8uUsoFE8aQ@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wjQ5Fpv0D7rxX0W=obx9xoOAxJ_Cr+pGCYOAi2S9FiCNg@mail.gmail.com>

Hi,

On Thu, Sep 5, 2019 at 1:20 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> You've at least now answered part of the "Why", but you didn't
> actually answer the whole "another developer" part.
It's certainly something we've wanted in the GNOME world for a long time:

See for instance

https://bugzilla.redhat.com/show_bug.cgi?id=991110

and

https://bugzilla.gnome.org/show_bug.cgi?id=707402

from all the way back 2013.  These are the alternatives I can think of:

- poll? status quo, but not great for obvious wakeup reasons
- use a different credential cache collection type that does support
change notification?
some of the other types do support change notification, but have their
own set of
problems. But maybe we should just go back to DIR type credential
cache collections
and try to figure out the life cycle problems they pose, i don't
know... or get more
man power behind KCM...
- manage change notification entirely from userspace.  assume credentials will
always be put in place from krb5-libs entry points, and just skip
notification if
it happens out from under the libraries. maybe upstream kerberos guys would
be onboard with this, I don't know. This seems less robust than having
the kernel
in the loop, though.

> I really don't like how nobody else than you seems to even look at any
> of the key handling patches. Because nobody else seems to care.
I've got no insight here, so i'll just throw a dart...

viro, is this something you have any interest in watching closer?

> See what I'm saying? This whole "David Howells does his own features
> that nobody else uses" needs to stop. You need to have a champion. I
> just don't feel safe pulling these kinds of changes from you, because
> I get the feeling that ABSOLUTELY NOBODY ELSE ever really looked at it
> or really cared.
I get the "one man is not enough for proper maintenance" argument, and
maybe it's true.  I don't know.

But I just want to point out, I have been asking dhowells for this change
notification API for years, so it's not something he did on his own and for
no particularly good reason. It solves a real problem and has a real-world
use case.

He kindly did it because I (and Robbie Harwood and others) asked him about
it, off and on, and  he was able to fit it onto his priority list for us.
From this thread, it sounds like he solved a problem for Greg too, killing a
couple birds with one stone?

--Ray

  reply index

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-04 22:15 [PATCH 00/11] Keyrings, Block and USB notifications [ver #8] David Howells
2019-09-04 22:15 ` [PATCH 01/11] uapi: General notification ring definitions " David Howells
2019-09-04 22:16 ` [PATCH 02/11] security: Add hooks to rule on setting a watch " David Howells
2019-09-04 22:16 ` [PATCH 03/11] security: Add a hook for the point of notification insertion " David Howells
2019-09-04 22:16 ` [PATCH 04/11] General notification queue with user mmap()'able ring buffer " David Howells
2019-09-04 22:16 ` [PATCH 05/11] keys: Add a notification facility " David Howells
2019-09-04 22:16 ` [PATCH 06/11] Add a general, global device notification watch list " David Howells
2019-09-04 22:16 ` [PATCH 07/11] block: Add block layer notifications " David Howells
2019-09-04 22:16 ` [PATCH 08/11] usb: Add USB subsystem " David Howells
2019-09-04 22:17 ` [PATCH 09/11] Add sample notification program " David Howells
2019-09-04 22:17 ` [PATCH 10/11] selinux: Implement the watch_key security hook " David Howells
2019-09-04 22:17 ` [PATCH 11/11] smack: Implement the watch_key and post_notification hooks " David Howells
2019-09-04 22:28 ` [PATCH 00/11] Keyrings, Block and USB notifications " Linus Torvalds
2019-09-05 17:01 ` Why add the general notification queue and its sources David Howells
2019-09-05 17:19   ` Linus Torvalds
2019-09-05 18:32     ` Ray Strode [this message]
2019-09-05 20:39       ` Linus Torvalds
2019-09-06 19:32         ` Ray Strode
2019-09-06 19:41           ` Ray Strode
2019-09-06 19:53           ` Robbie Harwood
2019-09-05 21:32       ` David Howells
2019-09-05 22:08         ` Linus Torvalds
2019-09-05 23:18         ` David Howells
2019-09-06  0:07           ` Linus Torvalds
2019-09-06 10:09           ` David Howells
2019-09-06 15:35             ` Linus Torvalds
2019-09-06 15:53               ` Linus Torvalds
2019-09-06 16:12                 ` Steven Whitehouse
2019-09-06 17:07                   ` Linus Torvalds
2019-09-06 17:14                     ` Linus Torvalds
2019-09-06 21:19                       ` David Howells
2019-09-06 17:14                   ` Andy Lutomirski
2019-09-05 18:37     ` Steven Whitehouse
2019-09-05 18:51       ` Ray Strode
2019-09-05 20:09         ` David Lehman
2019-09-05 18:33   ` Greg Kroah-Hartman

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