[Bug 711799] Re: e2fsprogs wrongly identifies ext4 as mounted

[Theodore Ts'o]

The directory names are not enciphered, they are replaced by unique
filenames AAA, BAA, CAA, DAA, etc.

The relevant section of code is:

		memset(cp, 'A', dirent->name_len);
		len = dirent->name_len;
		id = name_id[len]++;
		while ((len > 0) && (id > 0)) {
			*cp += id % 26;
			id = id / 26;
			cp++;
			len--;
		}

note the first thing done is to replace the file name with 'AAAA...'.
The rest is to change it up so the filenames are unique.

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https://bugs.launchpad.net/bugs/711799

Title:
  e2fsprogs wrongly identifies ext4 as mounted

Status in “e2fsprogs” package in Ubuntu:
  New

Bug description:
  Binary package hint: e2fsprogs

  After a crash of Ubuntu netbook, the machine hang with initramfs (I
  have a /boot and /).
  Booting with the same system (ubuntu 10.10) from thumb drive, I cannot fsck it:
  $ sudo fsck /dev/sda2
  fsck from util-linux-ng 2.17.2
  e2fsck 1.41.12 (17-May-2010)
  fsck.ext4: Device or resource busy while trying to open /dev/sda2
  Filesystem mounted or opened exclusively by another program?

  But it is not mounted:
  $ cat /proc/mounts
  shows that it is not mounted; and it can't be unmounted.

  dmesg knows what is going on:
  $ dmesg | grep sda2
  [    6.513953]  sda: sda1  [01;31m [Ksda2 [m [K sda3 < sda5 > sda4
  [    9.300388] EXT4-fs ( [01;31m [Ksda2 [m [K): INFO: recovery
  required on readonly filesystem
  [    9.300398] EXT4-fs ( [01;31m [Ksda2 [m [K): write access will be
  enabled during recovery
  [    9.312706] EXT4-fs warning (device  [01;31m [Ksda2 [m [K):
  ext4_clear_journal_err: Filesystem error recorded from previous mount:
  IO failure
  [    9.312729] EXT4-fs warning (device  [01;31m [Ksda2 [m [K):
  ext4_clear_journal_err: Marking fs in need of filesystem check.
  $
  But this fsck does never materialise, and can't be done manually.

  Finally, I tried to delete the journal, but to no avail, the "Device
  or resource busy" stays. Is there any way to trick fsck into believing
  me that it is not mounted?
  If not, I still consider the behaviour somewhat wrong: if not in
  /proc/mount, why does fsck say so?
  And when I
  sudo mount /dev/sda2 /mnt
  it starts the mount process, but never finishes, and also it is
  impossible to ever exit this process, I tried with Ctrl-C, Ctrl-Z, and
  even with kill -9 from another console. Ubuntu isn't even able to shut
  down then, but keeps trying forever.

  In a nutshell, it is a bug in 10.10. I use the installer-CD written to the thumb drive (Startup Disk creator).
   Confirmed: Because when I boot with a 9.04 thumb drive, I can easily open a terminal and run fsck. Done and over.

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