From: Greg KH <greg@kroah.com>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Andrey Borzenkov <arvidjaar@mail.ru>,
linux-hotplug-devel@lists.sourceforge.net,
linux-kernel@vger.kernel.org
Subject: Re: removable media revalidation - udev vs. devfs or static /dev
Date: Wed, 7 Jan 2004 11:50:33 -0800 [thread overview]
Message-ID: <20040107195032.GB823@kroah.com> (raw)
In-Reply-To: <Pine.LNX.4.58.0401071123490.12602@home.osdl.org>
On Wed, Jan 07, 2004 at 11:31:55AM -0800, Linus Torvalds wrote:
> On Wed, 7 Jan 2004, Greg KH wrote:
> > > But udev should probably also create all the sub-nodes if it doesn't
> > > already.
> >
> > It doesn't, as I thought we could rely on the kernel partition support.
>
> Indeed, we _can_ rely on the kernel partition support, but the subnodes
> are needed to get at those partitions.
>
> Obviously, a "repartitioning hotplug event" can create the subnodes, but
> that will fail exactly because it wouldn't allow the user to just access
> the nodes.
It sounds like just having the device node around will not cause the
rescan if you access it. I don't have any such devices here to test
this out or not. If true, having udev create all nodes will not help
out much :(
> > Hm, that would work, but what about a user program that just polls on
> > the device, as the rest of this thread discusses?
>
> I hate those "background CPU users". Have you looked at "ps" output after
> something like kscd has run, and does a CD check every second? It's
> _expensive_. It goes all the way down to the hardware, sends a request
> to the device.
Oh I know, it's one of the first things I disable when setting up a box :)
> Doing it every five minutes wouldn't be an issue, but doing it every five
> minutes would be absolutely _horrible_ from a user perspective standpoint.
> If you insert a smartmedia card in your cardreader, you expect to be able
> to access it pretty much immediately when you start typing. So a second or
> two of delay is fine, but even just five or ten seconds are already bad.
>
> So the choice is:
> - probe every removable device once a second
> - pre-populate the device nodes, and when the user presses the icon that
> says "mount", it will just do so. Immediately. No delay at all.
Based on the previous info, I think we are stuck with probing :(
> NOTE! We do have an alternative: if we were to just make block device
> nodes support "readdir" and "lookup", you could just do
>
> open("/dev/sda/1" ...)
>
> and it magically works right. I've wanted to do this for a long time, but
> every time I suggest allowing it, people scream.
Hm, that would be nice. I don't remember seeing it being proposed
before, what are the main complaints people have with this?
thanks,
greg k-h
next prev parent reply other threads:[~2004-01-07 19:50 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-01-01 20:33 removable media revalidation - udev vs. devfs or static /dev Andrey Borzenkov
2004-01-03 5:58 ` Greg KH
2004-01-03 8:51 ` Andrey Borzenkov
2004-01-03 12:37 ` Andries Brouwer
2004-01-03 12:42 ` Olaf Hering
2004-01-03 16:05 ` Andrey Borzenkov
2004-01-03 17:54 ` Jens Axboe
2004-01-07 9:43 ` Olaf Hering
2004-01-07 9:50 ` Jens Axboe
2004-01-07 9:56 ` Olaf Hering
2004-01-07 9:59 ` Jens Axboe
2004-01-07 10:25 ` Olaf Hering
2004-01-07 10:31 ` Jens Axboe
2004-01-07 10:47 ` Andrey Borzenkov
2004-01-07 10:54 ` Jens Axboe
2004-01-07 17:56 ` Greg KH
2004-01-30 12:59 ` Olaf Hering
2004-01-07 11:00 ` Andrey Borzenkov
2004-01-07 11:05 ` Jens Axboe
2004-01-07 11:14 ` Andrey Borzenkov
2004-01-07 11:16 ` Jens Axboe
2004-01-03 20:51 ` Greg KH
2004-01-07 18:38 ` Linus Torvalds
2004-01-07 18:57 ` Greg KH
2004-01-07 19:23 ` Mika Penttilä
2004-01-07 19:24 ` Greg KH
2004-01-07 19:31 ` Mika Penttilä
2004-01-08 1:38 ` Linus Torvalds
2004-01-07 19:31 ` Linus Torvalds
2004-01-07 19:50 ` Greg KH [this message]
2004-01-07 20:25 ` Richard Troth
2004-01-07 20:38 ` Valdis.Kletnieks
2004-01-07 23:34 ` Greg KH
2004-01-08 0:32 ` Martin J. Bligh
2004-01-08 0:41 ` Greg KH
2004-01-08 1:07 ` Martin J. Bligh
2004-01-08 1:15 ` Greg KH
2004-01-08 1:50 ` Martin J. Bligh
2004-01-08 18:34 ` Martin Schlemmer
2004-01-08 1:48 ` Linus Torvalds
2004-01-08 14:06 ` "Andrey Borzenkov"
2004-01-08 0:42 ` viro
2004-01-08 1:16 ` Greg KH
2004-01-09 3:36 ` Joel Becker
2004-01-09 9:49 ` Gerd Knorr
2004-01-12 17:16 ` Joel Becker
2004-01-12 23:08 ` J.A. Magallon
2004-01-07 20:52 ` Olaf Hering
2004-01-08 2:03 ` Linus Torvalds
2004-01-08 4:16 ` Gene Heskett
2004-01-08 4:23 ` Linus Torvalds
2004-01-08 7:45 ` Olaf Hering
2004-01-08 2:13 ` Andries Brouwer
2004-01-08 2:19 ` Linus Torvalds
2004-01-08 2:49 ` Andries Brouwer
2004-01-08 2:56 ` Linus Torvalds
2004-01-08 3:35 ` Andries Brouwer
2004-01-08 3:43 ` Linus Torvalds
2004-01-08 8:00 ` Xavier Bestel
2004-01-09 0:28 ` Robert Love
2004-01-09 0:52 ` Linus Torvalds
2004-01-09 1:16 ` Matt Mackall
2004-01-08 10:32 ` Éric Brunet
2004-01-08 5:19 Iqbal
2004-01-12 9:09 Ling, Xiaofeng
2004-01-12 13:02 Nicolas Mailhot
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