[Bug 499773] Re: Race with ureadahead can mean that /var/lib/ureadahead/debugfs appears in /etc/mtab

[Håkan Jonsson]

It is not harmless. I am also getting file system full errors. For
example, Mozilla Firefox, can't download anything since it can't store
any temp files.

$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_local-root
                       19G   19G     0 100% /
none                  5.9G  280K  5.9G   1% /dev
none                  5.9G  1.3M  5.9G   1% /dev/shm
none                  5.9G  468K  5.9G   1% /var/run
none                  5.9G     0  5.9G   0% /var/lock
none                  5.9G     0  5.9G   0% /lib/init/rw
none                   19G   19G     0 100% /var/lib/ureadahead/debugfs
/dev/sda1             457M  116M  317M  27% /boot
/dev/mapper/vg_local-home
                      159G   47G  105G  31% /home

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https://bugs.launchpad.net/bugs/499773

Title:
  Race with ureadahead can mean that /var/lib/ureadahead/debugfs appears
  in /etc/mtab

Status in “mountall” package in Ubuntu:
  Triaged

Bug description:
  When the system is booted, the mountall process may notice a
  temporarily-mounted file system at /var/lib/ureadahead/debugfs and
  record that fact in /etc/mtab.  Later in the boot process, this file
  system is unmounted, but mountall doesn't record unmounts, so it never
  "forgets" this path when it's unmounted.

  Mountall should if necessary remove this mount from mtab.

  To confirm on your system that it is indeed not really mounted, look for it in /proc/self/mountinfo
  Otherwise this may be due to a crash of the ureadahead process during boot.

  ---- original report ----

  Binary package hint: ureadahead

  $ mount
  /dev/sda1 on / type ext3 (rw,relatime,errors=remount-ro)
  proc on /proc type proc (rw)
  none on /sys type sysfs (rw,noexec,nosuid,nodev)
  none on /sys/fs/fuse/connections type fusectl (rw)
  none on /sys/kernel/debug type debugfs (rw)
  none on /sys/kernel/security type securityfs (rw)
  udev on /dev type tmpfs (rw,mode=0755)
  none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
  none on /dev/shm type tmpfs (rw,nosuid,nodev)
  none on /var/run type tmpfs (rw,nosuid,mode=0755)
  none on /var/lock type tmpfs (rw,noexec,nosuid,nodev)
  none on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
  none on /var/lib/ureadahead/debugfs type debugfs (rw)
  /dev/sda6 on /home type ext4 (rw,relatime)
  binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)
  gvfs-fuse-daemon on /home/hildeb/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=hildeb)

  /var/lib/ureadahead/debugfs is left lingering around. It's use is
  somewhat limited, since most Ubuntu users are not kernel developers --
  if it's used as intended: http://kerneltrap.org/node/4394

  ProblemType: Bug
  Architecture: amd64
  Date: Wed Dec 23 11:04:11 2009
  DistroRelease: Ubuntu 9.10
  NonfreeKernelModules: nvidia
  Package: ureadahead 0.90.3-2
  ProcEnviron:
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcVersionSignature: Ubuntu 2.6.31-17.54-generic
  SourcePackage: ureadahead
  Uname: Linux 2.6.31-17-generic x86_64

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