GNU bug report logs - #53212
feature request: mount option to specify the device number

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Package: coreutils;

Reported by: Joachim Wagner <jo2l <at> mqzmail.eu>

Date: Wed, 12 Jan 2022 17:01:02 UTC

Severity: wishlist

Tags: notabug

Done: Bernhard Voelker <mail <at> bernhard-voelker.de>

Bug is archived. No further changes may be made.

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Report forwarded to bug-coreutils <at> gnu.org:
bug#53212; Package coreutils. (Wed, 12 Jan 2022 17:01:02 GMT) Full text and rfc822 format available.

Acknowledgement sent to Joachim Wagner <jo2l <at> mqzmail.eu>:
New bug report received and forwarded. Copy sent to bug-coreutils <at> gnu.org. (Wed, 12 Jan 2022 17:01:02 GMT) Full text and rfc822 format available.

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Joachim Wagner <jo2l <at> mqzmail.eu>
To: bug-coreutils <at> gnu.org
Subject: feature request: mount option to specify the device number
Date: Wed, 12 Jan 2022 16:59:52 +0000
Not sure whether this is coreutils or kernel. Maybe both.

A filesystem's device number such as reported by `stat` can be derived from 
major and minor of the underlying block device, e.g. xfs, or be allocated at 
mount time, e.g. btrfs. Even in the former case, the device number can change 
between restarts, e.g. when multiple dm-crypt devices are created in different 
order. Changing device numbers cause trouble for applications that use the 
device number to identify a filesystem across restarts, e.g. KDE's baloo file 
indexer.

A mount option to specify the device number would fix this trouble without 
requiring applications to move to alternative ways of identifying filesystems, 
e.g. based on UUIDs. This option could be general, i.e. the device number can 
be set for any filesystem, including those that normally derive it from major 
and minor of their block device(s).

The implementation would probably be simplified if the specified device 
numbers must come from a reserved pool. Otherwise, care must be taken that the 
numbers do not collide with automatically assigned device numbers, including 
those allocated later.

Replaces bug #53209

References:
https://bugs.kde.org/show_bug.cgi?id=402154
https://bugs.kde.org/show_bug.cgi?id=404057
https://bugs.kde.org/show_bug.cgi?id=413694
https://unix.stackexchange.com/questions/345220/btrfs-how-to-get-real-device-id
https://stackoverflow.com/questions/4309882/device-number-in-stat-command-output/4309947










Information forwarded to bug-coreutils <at> gnu.org:
bug#53212; Package coreutils. (Wed, 12 Jan 2022 17:47:01 GMT) Full text and rfc822 format available.

Message #8 received at 53212 <at> debbugs.gnu.org (full text, mbox):

From: Bernhard Voelker <mail <at> bernhard-voelker.de>
To: Joachim Wagner <jo2l <at> mqzmail.eu>, 53212 <at> debbugs.gnu.org
Subject: Re: bug#53212: feature request: mount option to specify the device
 number
Date: Wed, 12 Jan 2022 18:46:33 +0100
tag 53212 notabug
close 53212
stop

On 1/12/22 17:59, Joachim Wagner wrote:
> Not sure whether this is coreutils or kernel. Maybe both.
> 
> A filesystem's device number such as reported by `stat` can be derived from 
> major and minor of the underlying block device, e.g. xfs, or be allocated at 
> mount time, e.g. btrfs. Even in the former case, the device number can change 
> between restarts, e.g. when multiple dm-crypt devices are created in different 
> order. Changing device numbers cause trouble for applications that use the 
> device number to identify a filesystem across restarts, e.g. KDE's baloo file 
> indexer.
> 
> A mount option to specify the device number would fix this trouble without 
> requiring applications to move to alternative ways of identifying filesystems, 
> e.g. based on UUIDs. This option could be general, i.e. the device number can 
> be set for any filesystem, including those that normally derive it from major 
> and minor of their block device(s).
> 
> The implementation would probably be simplified if the specified device 
> numbers must come from a reserved pool. Otherwise, care must be taken that the 
> numbers do not collide with automatically assigned device numbers, including 
> those allocated later.
> 
> Replaces bug #53209
> 
> References:
> https://bugs.kde.org/show_bug.cgi?id=402154
> https://bugs.kde.org/show_bug.cgi?id=404057
> https://bugs.kde.org/show_bug.cgi?id=413694
> https://unix.stackexchange.com/questions/345220/btrfs-how-to-get-real-device-id
> https://stackoverflow.com/questions/4309882/device-number-in-stat-command-output/4309947

mount is a command from the util-linux package, hence you'd be better off asking
on their mailing list <util-linux <at> vger.kernel.org>.

FWIW: mount already knows quite a list of alternatives how to specify the source
device:

  mount --help | sed -n '/^Source:/,/^$/p'
  Source:
   -L, --label <label>     synonym for LABEL=<label>
   -U, --uuid <uuid>       synonym for UUID=<uuid>
   LABEL=<label>           specifies device by filesystem label
   UUID=<uuid>             specifies device by filesystem UUID
   PARTLABEL=<label>       specifies device by partition label
   PARTUUID=<uuid>         specifies device by partition UUID
   ID=<id>                 specifies device by udev hardware ID
   <device>                specifies device by path
   <directory>             mountpoint for bind mounts (see --bind/rbind)
   <file>                  regular file for loopdev setup

As this is not related to coreutils, I'm hereby closing this issue in our
bug tracker.

Have a nice day,
Berny




Added tag(s) notabug. Request was from Bernhard Voelker <mail <at> bernhard-voelker.de> to control <at> debbugs.gnu.org. (Wed, 12 Jan 2022 17:47:02 GMT) Full text and rfc822 format available.

bug closed, send any further explanations to 53212 <at> debbugs.gnu.org and Joachim Wagner <jo2l <at> mqzmail.eu> Request was from Bernhard Voelker <mail <at> bernhard-voelker.de> to control <at> debbugs.gnu.org. (Wed, 12 Jan 2022 17:47:02 GMT) Full text and rfc822 format available.

Information forwarded to bug-coreutils <at> gnu.org:
bug#53212; Package coreutils. (Thu, 13 Jan 2022 10:41:01 GMT) Full text and rfc822 format available.

Message #15 received at 53212 <at> debbugs.gnu.org (full text, mbox):

From: Joachim Wagner <jo2l <at> mqzmail.eu>
To: 53212 <at> debbugs.gnu.org
Cc: Bernhard Voelker <mail <at> bernhard-voelker.de>
Subject: Re: bug#53212: feature request: mount option to specify the device
 number
Date: Thu, 13 Jan 2022 10:39:52 +0000
> mount is a command from the util-linux package, hence you'd be better off
> asking on their mailing list <util-linux <at> vger.kernel.org>.

Thanks Berny pointing me in this direction.

> FWIW: mount already knows quite a list of alternatives how to specify the
> source device [...]

Clarification: This feature is not about the source device but the "device 
number" reported by the filesystem in `stat()`. For xfs and probably many 
other filesystems, this happens to be (major<<8)+minor of the source device 
but btrfs, for example, allocates a new number for each subvolume.

Joachim








Information forwarded to bug-coreutils <at> gnu.org:
bug#53212; Package coreutils. (Thu, 13 Jan 2022 11:02:02 GMT) Full text and rfc822 format available.

Message #18 received at 53212 <at> debbugs.gnu.org (full text, mbox):

From: Joachim Wagner <jo2l <at> mqzmail.eu>
To: 53212 <at> debbugs.gnu.org
Subject: Re: bug#53212: feature request: mount option to specify the device
 number
Date: Thu, 13 Jan 2022 11:01:00 +0000
created https://github.com/util-linux/util-linux/issues/1562






bug archived. Request was from Debbugs Internal Request <help-debbugs <at> gnu.org> to internal_control <at> debbugs.gnu.org. (Thu, 10 Feb 2022 12:24:05 GMT) Full text and rfc822 format available.

This bug report was last modified 3 years and 188 days ago.

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