cowbuilder deletes bind-mounted directories

[Jean-Baptiste Lallement]

If cowbuilder failed to unmount a bind-mounted directory (device busy for example) it unconditionally deletes its content during the clean-up phase.

Excerpt from a log with this bug (complete log attached)
=====
I: umounting /var/lib/jenkins/cu2d
umount: /var/cache/pbuilder/build/cow.15281/var/lib/jenkins/cu2d: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
[...]
 -> Cleaning COW directory
  forking: rm -rf /var/cache/pbuilder/build//cow.1195
rm: cannot remove `/var/cache/pbuilder/build//cow.1195/var/cache/pbuilder/ccache': Device or resource busy
rm: cannot remove `/var/cache/pbuilder/build//cow.1195/var/lib/jenkins/cu2d/work/experimental/100scopes': Device or resource busy
rm: cannot remove `/var/cache/pbuilder/build//cow.1195/var/lib/jenkins/cu2d/launchpad.cache': Directory not empty
=====

The 'rm' command must skip directories on other filesystems

This bug occurs when pbuilder fails to mount a bindmounted directory, then fails to unmount previously successfully mounted directories. This condition is not so rare when executing several cowbuilder processes in parallel using the same bind-mounted directories.

There is no easy way to reproduce this issue:
- Start several cowbuilder in parallel (in our system we run around 40) and bind mount the same source directories
- patch /usr/lib/pbuilder/pbuilder-modules lines 275 to 291 to fail on 2nd bindmount then fail when it tries to unmount one of the successfully mounted directory.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: cowbuilder 0.71
ProcVersionSignature: Ubuntu 3.8.0-12.21-generic 3.8.2
Uname: Linux 3.8.0-12-generic x86_64
ApportVersion: 2.9.1-0ubuntu1
Architecture: amd64
Date: Mon Mar 18 11:08:38 2013
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: cowdancer
UpgradeStatus: Upgraded to raring on 2012-01-31 (411 days ago)

[Jean-Baptiste Lallement (jibel)]

This patch checks if a directory is mounted under the chroot and skips rmrf() if there is one.

[Brian Murray (brian-murray)]

I updated the changelog for raring and ran update-maintainer to change Maintainer to Ubuntu Developers before uploading your patch. Thanks for the fix.

[Launchpad Janitor (janitor)]

This bug was fixed in the package cowdancer - 0.71ubuntu1

---------------
cowdancer (0.71ubuntu1) raring; urgency=low

  * A directory bind-mounted into pc->buildplace, will be cleaned out by
    rmrf() To avoid this disaster, we skip buildplace clean-up if a directory
    is bind-mounted under the chroot (LP: #1156540)
 -- Jean-Baptiste Lallement <email address hidden> Tue, 19 Mar 2013 09:35:26 +0100