[Bug 1640823] [NEW] [trusty] limited to 8 loop devices

[Martin Pitt]

Public bug reported:

trusty has a very old util-linux which does not yet know about /dev
/loop-control to create arbitrarily many loop devices. This feature was
introduced in Linux 3.1 already (i. e. before precise even). This is a
showstopper for backporting snappy as that needs a lot of loop mounts.

Support for loop-control got introduced in
http://git.kernel.org/cgit/utils/util-linux/util-
linux.git/commit/?id=0b14bf7a

SRU TEST CASE:
$ for i in `seq 20`; do echo $i; sudo losetup --find --show /etc/issue; done

With current trusty's util-linux this will only work for 8 loop devices
and then start failing:

8
/dev/loop7
9
losetup: could not find any free loop device
[...]

With the proposed version, they should all work.

REGRESSION POTENTIAL: /dev/loop-control and the corresponding util-linux
support has exited for a long time without known/major issues, so this
should be fairly safe. Also, the patch falls back to the previous
"iterate over loop0 to loop7" behaviour if loop-control is not
available.

** Affects: util-linux (Ubuntu)
     Importance: Undecided
         Status: Fix Released

** Affects: util-linux (Ubuntu Trusty)
     Importance: Undecided
         Status: Triaged

** Also affects: util-linux (Ubuntu Trusty)
   Importance: Undecided
       Status: New

** Changed in: util-linux (Ubuntu)
       Status: New => Fix Released

** Changed in: util-linux (Ubuntu Trusty)
       Status: New => Triaged

** Description changed:

  trusty has a very old util-linux which does not yet know about /dev
  /loop-control to create arbitrarily many loop devices. This feature was
  introduced in Linux 3.1 already (i. e. before precise even). This is a
  showstopper for backporting snappy as that needs a lot of loop mounts.
  
  Support for loop-control got introduced in
  http://git.kernel.org/cgit/utils/util-linux/util-
  linux.git/commit/?id=0b14bf7a
  
  SRU TEST CASE:
  $ for i in `seq 20`; do echo $i; sudo losetup --find --show /etc/issue; done
  
  With current trusty's util-linux this will only work for 8 loop devices
  and then start failing:
  
  8
  /dev/loop7
  9
  losetup: could not find any free loop device
  [...]
  
  With the proposed version, they should all work.
  
  REGRESSION POTENTIAL: /dev/loop-control and the corresponding util-linux
  support has exited for a long time without known/major issues, so this
- should be fairly safe.
+ should be fairly safe. Also, the patch falls back to the previous
+ "iterate over loop0 to loop7" behaviour if loop-control is not
+ available.

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https://bugs.launchpad.net/bugs/1640823

Title:
  [trusty] limited to 8 loop devices

Status in util-linux package in Ubuntu:
  Fix Released
Status in util-linux source package in Trusty:
  Triaged

Bug description:
  trusty has a very old util-linux which does not yet know about /dev
  /loop-control to create arbitrarily many loop devices. This feature
  was introduced in Linux 3.1 already (i. e. before precise even). This
  is a showstopper for backporting snappy as that needs a lot of loop
  mounts.

  Support for loop-control got introduced in
  http://git.kernel.org/cgit/utils/util-linux/util-
  linux.git/commit/?id=0b14bf7a

  SRU TEST CASE:
  $ for i in `seq 20`; do echo $i; sudo losetup --find --show /etc/issue; done

  With current trusty's util-linux this will only work for 8 loop
  devices and then start failing:

  8
  /dev/loop7
  9
  losetup: could not find any free loop device
  [...]

  With the proposed version, they should all work.

  REGRESSION POTENTIAL: /dev/loop-control and the corresponding util-
  linux support has exited for a long time without known/major issues,
  so this should be fairly safe. Also, the patch falls back to the
  previous "iterate over loop0 to loop7" behaviour if loop-control is
  not available.

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