Bug 24279

Summary:	Handling devices in use disappearing
Product:	udisks	Reporter:	David Zeuthen (not reading bugmail) <zeuthen>
Component:	general	Assignee:	David Zeuthen (not reading bugmail) <zeuthen>
Status:	RESOLVED FIXED	QA Contact:
Severity:	normal
Priority:	medium	CC:	kay
Version:	unspecified
Hardware:	Other
OS:	All
Whiteboard:
i915 platform:		i915 features:

Description David Zeuthen (not reading bugmail) 2009-10-02 10:14:42 UTC

Some times devices disappear when they are still in use (e.g. mounted, part of an array, LUKS partition that is set-up). This can happen because users yank the device or the device fails.

Right now we have some code for dealing with these situations but the code is not very robust and it would probably be best to just leave that task to the kernel where it belongs.

This bug is for discussing how to best handle this.

Comment 1 David Zeuthen (not reading bugmail) 2009-10-23 15:06:34 UTC

Bug 24708 is related to this.

Comment 2 David Zeuthen (not reading bugmail) 2009-10-23 15:22:04 UTC

I talked to Kay about this some time ago and we ended up with something like this

First, we can't really make the kernel be super clever about these things; while the status quo is decidedly broken for desktop workloads there are other (server) workloads where this degree of "policy" (e.g. auto-unmounting, auto-teardown) is unwanted. Mostly due to cascading effects, making things harder to debug and, well, the status quo.

Second, we want to do the right thing for devices set up via DeviceKit-disks.

Third, we want to make it possible for admins for "the right thing" to happen even for devices not set up via DeviceKit-disks. This should be achieved by having a DKD_CLEANUP udev property that admins can set to 1 on a per-device basis.

Now, "the right thing" includes

 1. force/lazy unmounting filesystems when the device goes away

   - this includes things mounted via /etc/fstab through
     FilesystemMount() which we don't do right now (bug 24708)

 2. force removal of MD RAID components when the component device goes
    away

 3. force shutdown of a MD RAID array when an insufficient number of
    components are available

 4. ditto for device-mapper - right now only dm-crypt/LUKS use cases
    are interesting but eventually we want to support LVM2 (bug 24599)

 5. ditto for other things

Comment 3 David Zeuthen (not reading bugmail) 2012-09-28 15:07:50 UTC

These days udisks handles this by only tearing down stuff (mounts, crypto) set up via udisks and this seems to work fine. Closing.

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