[Bug 956038] Re: resize2fs allows resize beyond maximum fs size - corrupts fs

[Theodore Ts'o]

Yes, sorry, there are two different problems here.  The one I was
talking about happens when you go above 16TB.   That fix is easy.

Going to a fs size a little greater than 1TB is triggering another
problem from a file system originally created with 1G file size, which
I've replicated and I've confirmed that it's taking place on 1.42.x as
well as e2fspros 1.41.x.  The problem is that when we run out of
reserved GDT blocks, resize2fs isn't noticing and ends up corrupting the
file system.

The workaround for now is to explicitly create the file system with an
expected maximum resize: mke2fs -t ext4 -E resize=8T /dev/tiny

You'll need to do this if you want to resize to succeed in any case.  I
agree resize2fs should notice this case and deal with it more
intelligently.

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https://bugs.launchpad.net/bugs/956038

Title:
  resize2fs allows resize beyond maximum fs size - corrupts fs

Status in “e2fsprogs” package in Ubuntu:
  Confirmed

Bug description:
  If you resize a 1G partition to more than 1T the filesystem becomes
  corrupted offline and errors on-line.

  resize2fs does not check the maximum size of the filesystem before
  initiating the resize.

  To reproduce:

  $ dd if=/dev/zero of=tiny bs=1 count=0 seek=1G
  $ mkfs.ext4 -F -J size=128 tiny

  ....
  Maximum filesystem blocks=268435456
  ....
  $ cp tiny xxl
  $ resize2fs xxl 1310720M

  resize2fs 1.42 (29-Nov-2011)
  Resizing the filesystem on xxl to 335544320 (4k) blocks.
  The filesystem on xxl is now 335544320 blocks long.

  $ e2fsck xxl
  e2fsck 1.42 (29-Nov-2011)
  e2fsck: Group descriptors look bad... trying backup blocks...
  One or more block group descriptor checksums are invalid.  Fix<y>?

  ProblemType: Bug
  DistroRelease: Ubuntu 11.10
  Package: e2fsprogs 1.41.14-1ubuntu3
  ProcVersionSignature: Ubuntu 3.0.0-16.29-generic 3.0.20
  Uname: Linux 3.0.0-16-generic x86_64
  ApportVersion: 1.23-0ubuntu4
  Architecture: amd64
  CheckboxSubmission: 55cafa5b8b82ed224cc59d444cb1fc25
  CheckboxSystem: 3e53d3ea5811723345f19eff5070f9ab
  Date: Thu Mar 15 13:51:37 2012
  InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
  SourcePackage: e2fsprogs
  UpgradeStatus: No upgrade log present (probably fresh install)

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