From: Ian Kent <raven@themaw.net>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: David Howells <dhowells@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Casey Schaufler <casey@schaufler-ca.com>,
Stephen Smalley <sds@tycho.nsa.gov>,
Nicolas Dichtel <nicolas.dichtel@6wind.com>,
Christian Brauner <christian@brauner.io>,
andres@anarazel.de, Jeff Layton <jlayton@redhat.com>,
dray@redhat.com, Karel Zak <kzak@redhat.com>,
keyrings@vger.kernel.org, Linux API <linux-api@vger.kernel.org>,
linux-fsdevel@vger.kernel.org,
LSM <linux-security-module@vger.kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 13/17] watch_queue: Implement mount topology and attribute change notifications [ver #5]
Date: Wed, 05 Aug 2020 19:36:05 +0800 [thread overview]
Message-ID: <013e9bb3cb1536c73a5b58c5ff000b3b00629561.camel@themaw.net> (raw)
In-Reply-To: <CAJfpegvxKTy+4Zk6banvxQ83PeFV7Xnt2Qv=kkOg57rxFKqVEg@mail.gmail.com>
On Wed, 2020-08-05 at 09:43 +0200, Miklos Szeredi wrote:
> On Wed, Aug 5, 2020 at 3:54 AM Ian Kent <raven@themaw.net> wrote:
> > > > It's way more useful to have these in the notification than
> > > > obtainable
> > > > via fsinfo() IMHO.
> > >
> > > What is it useful for?
> >
> > Only to verify that you have seen all the notifications.
> >
> > If you have to grab that info with a separate call then the count
> > isn't necessarily consistent because other notifications can occur
> > while you grab it.
>
> No, no no. The watch queue will signal an overflow, without any
> additional overhead for the normal case. If you think of this as a
> protocol stack, then the overflow detection happens on the transport
> layer, instead of the application layer. The application layer is
> responsible for restoring state in case of a transport layer error,
> but detection of that error is not the responsibility of the
> application layer.
I can see in the kernel code that an error is returned if the message
buffer is full when trying to add a message, I just can't see where
to get it in the libmount code.
That's not really a communication protocol problem.
Still I need to work out how to detect it, maybe it is seen by
the code in libmount already and I simply can't see what I need
to do to recognise it ...
So I'm stuck wanting to verify I have got everything that was
sent and am having trouble moving on from that.
Ian
next prev parent reply other threads:[~2020-08-05 20:14 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-18 15:03 [PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #5] David Howells
2020-03-18 15:03 ` [PATCH 01/17] uapi: General notification queue definitions " David Howells
2020-03-18 15:03 ` [PATCH 02/17] security: Add hooks to rule on setting a watch " David Howells
2020-03-18 18:56 ` James Morris
2020-03-18 15:03 ` [PATCH 03/17] security: Add a hook for the point of notification insertion " David Howells
2020-03-18 18:57 ` James Morris
2020-03-18 15:03 ` [PATCH 04/17] pipe: Add O_NOTIFICATION_PIPE " David Howells
2020-03-18 15:03 ` [PATCH 05/17] pipe: Add general notification queue support " David Howells
2020-03-18 15:04 ` [PATCH 06/17] watch_queue: Add a key/keyring notification facility " David Howells
2020-03-18 19:04 ` James Morris
2020-03-18 15:04 ` [PATCH 07/17] Add sample notification program " David Howells
2020-03-18 15:04 ` [PATCH 08/17] pipe: Allow buffers to be marked read-whole-or-error for notifications " David Howells
2020-03-18 15:04 ` [PATCH 09/17] pipe: Add notification lossage handling " David Howells
2020-03-18 15:04 ` [PATCH 10/17] selinux: Implement the watch_key security hook " David Howells
2020-03-18 19:06 ` James Morris
2020-03-18 15:04 ` [PATCH 11/17] smack: Implement the watch_key and post_notification hooks " David Howells
2020-03-18 15:05 ` [PATCH 12/17] watch_queue: Add security hooks to rule on setting mount and sb watches " David Howells
2020-03-18 19:07 ` James Morris
2020-03-18 15:05 ` [PATCH 13/17] watch_queue: Implement mount topology and attribute change notifications " David Howells
2020-04-02 15:19 ` Miklos Szeredi
2020-06-14 3:07 ` Ian Kent
2020-06-15 8:44 ` Miklos Szeredi
2020-07-23 10:48 ` David Howells
2020-08-03 9:29 ` Miklos Szeredi
2020-08-04 11:38 ` Ian Kent
2020-08-04 13:19 ` Miklos Szeredi
2020-08-05 1:53 ` Ian Kent
2020-08-05 7:43 ` Miklos Szeredi
2020-08-05 11:36 ` Ian Kent [this message]
2020-08-05 11:56 ` Miklos Szeredi
2020-07-24 10:19 ` David Howells
2020-07-24 10:44 ` Ian Kent
2020-07-24 11:36 ` David Howells
2020-08-03 10:02 ` Miklos Szeredi
2020-08-03 10:08 ` David Howells
2020-08-03 10:18 ` David Howells
2020-08-03 11:17 ` Miklos Szeredi
2020-08-03 11:49 ` David Howells
2020-08-03 12:01 ` Ian Kent
2020-08-03 12:31 ` David Howells
2020-08-03 14:30 ` Ian Kent
2020-03-18 15:05 ` [PATCH 14/17] watch_queue: sample: Display mount tree " David Howells
2020-03-18 15:05 ` [PATCH 15/17] watch_queue: Introduce a non-repeating system-unique superblock ID " David Howells
2020-03-18 15:05 ` [PATCH 16/17] watch_queue: Add superblock notifications " David Howells
2020-03-18 15:05 ` [PATCH 17/17] watch_queue: sample: Display " David Howells
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