Re: How to fix CDROM/DVD eject mess?

From: Austin S Hemmelgarn
Date: Mon Feb 02 2015 - 15:03:17 EST

On 2015-02-02 14:34, Maciej W. Rozycki wrote:
On Mon, 2 Feb 2015, Kay Sievers wrote:

I thought that fixing the udev behavior would solve the problem. But
it turned out that I was too naive. A bigger problem is that all
user-space stuff misinterprets DISK_EVENT_EJECT_REQUEST event: they
see this as if the disk is *ready* to be ejected. KDE, for example,
dismisses the DVD icon when it receives this event even if it's still
mounted.

It is not really about being "ready to eject", if the user presses the
button, the user does not want to wait for anything else than actually
ejecting the media as fast as possible. It is the same as ripping out
a USB cable. It needs to work, no matter if things are mounted or
busy.

All the technical details aside, this is a bold statement -- how do you
know what the user actually wants?

I for one want to see the medium locked if in use, just as it has been
since 1990s. If I wanted to do an emergency eject (the equivalent of
ripping out a USB cable), then I would use a paperclip in the manual eject
hole. So you've got a counterexample to your assertion now. All people
are not the same.

All I want to say here is there seems to be a policy hidden somewhere
here where it should not. It's up to the user to decide what suits him or
her. We just need to give them the right tools.

It is just a hardware button event which should not be masked out for
rather weird reasons.

Precisely, and I should have a way to control it. If I used a GUI, I
might want the event to pop up a window with the list of current users
(accessing processes) of the device, perhaps asking if to terminate them.
Or flip a relay to make my kettle boil water.

I agree, there should be some option to control this, although personally, I would prefer two options, one for when it's read-only (in which case I would prefer the current behavior), and one for when it's read-write (in which case, I would prefer that the door-lock be engaged).

Also, udev's current response isn't all that great either, when it get's the event, it should do a lazy unmount of the device. Windows and OS X automatically unmount filesystems from ejected media, so it is expected behavior for many users (and I keep meaning to open a bug against udev because of this, but keep forgetting).

The fact that it stays mounted can cause all kinds of confusing issues as well if the user inserts a different disc; I've seen cases (recently in fact) where a new disc was inserted and due to caching, it showed dentries from the old disc, but with the files full of gibberish, and it refused to unmount the (now invalid) filesystem without using umount -f (which shouldn't be needed for a read-only FS, period).


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