[Bug 1844012] Re: grub2 doesn't recognize ext4 with metadata_csum_seed enabled

[Jim Bray]

** Summary changed:

- grub2 doesn't recognize ext4 with metadata_csum enabled
+ grub2 doesn't recognize ext4 with metadata_csum_seed enabled

** Description changed:

  (probably)/usr/lib/grub/x86_64-efi/ext2.mod, from:
  
  grub-efi-amd64-bin:
    Installed: 2.02-2ubuntu8.13
    Candidate: 2.02-2ubuntu8.13
  
- doesn't recognize an ext4 filesystem with metadata_csum set.
+ doesn't recognize an ext4 filesystem with metadata_csum_seed set.
  
  This is true in command-line grub, not just the update-grub software.
  Attempting
  
  linux (hdx,gptx)/vm etc on an ext4 fs with metadata_csum enabled fails;
  removing the metadata_csum option fixes this.
  
- Oddly enough it doesn't fail with this error, from grub-core/fs/ext2.c:
+ The failure is "unrecognized filesystem" for any ext4 fs with
+ metadata_csum_seed set. Apparently saving the metata checksum seed in
+ the superblock changes it beyond recognition for grub.
  
- grub_error (GRUB_ERR_BAD_FS, "filesystem has unsupported incompatible
- features");
- 
- I will recreate the bug and get a precise error message and append it.
- 
- 
- I tried to install latest grub from eaon to see if upstream has fixed this, but it depended on too much other unreleased software such as libc6.
+ I tried to install latest grub from eaon to see if upstream has fixed
+ this, but it depended on too much other unreleased software such as
+ libc6.
  
  I pulled the 2.04 source. There is nothing in the Changelog that appears
  to address this.
  
  
  from `man ext4`:
- "metadata_csum
-               This  ext4  feature  enables metadata checksumming.  This feature stores checksums for all of the filesystem metadata (superblock, group descriptor blocks, inode and block bitmaps, directories, and extent tree blocks).
-               The checksum algorithm used for the metadata blocks is different than the one used for group descriptors with the uninit_bg feature.  These two features are incompatible and metadata_csum will  be  used  preferentially
-               instead of uninit_bg."
+  metadata_csum_seed
+               This feature allows the filesystem to store the metadata checksum seed in the superblock, which allows the administrator to change the UUID of a filesystem using the metadata_csum feature while it is mounted.

** Tags removed: metadata-csum
** Tags added: metadata-csum-seed

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https://bugs.launchpad.net/bugs/1844012

Title:
  grub2 doesn't recognize ext4 with metadata_csum_seed enabled

Status in grub2 package in Ubuntu:
  New

Bug description:
  (probably)/usr/lib/grub/x86_64-efi/ext2.mod, from:

  grub-efi-amd64-bin:
    Installed: 2.02-2ubuntu8.13
    Candidate: 2.02-2ubuntu8.13

  doesn't recognize an ext4 filesystem with metadata_csum_seed set.

  This is true in command-line grub, not just the update-grub software.
  Attempting

  linux (hdx,gptx)/vm etc on an ext4 fs with metadata_csum enabled
  fails; removing the metadata_csum_seed option fixes this.

  The failure is "unknown filesystem" for any ext4 fs with metadata_csum_seed set. Apparently saving the metata checksum seed in the superblock changes it beyond recognition for grub. The message appears to be coming from 
  grub-2.04/grub-core/kern /fs.c:

  grub_fs_t
  grub_fs_probe (grub_device_t device)
  {....
   grub_error (GRUB_ERR_UNKNOWN_FS, N_("unknown filesystem"));
  }

  
  I tried to install latest grub from eaon to see if upstream has fixed this, but it depended on too much other unreleased software such as libc6.

  I pulled the 2.04 source. There is nothing in the Changelog that
  appears to address this.

  
  from `man ext4`:
   metadata_csum_seed
                This feature allows the filesystem to store the metadata checksum seed in the superblock, which allows the administrator to change the UUID of a filesystem using the metadata_csum feature while it is mounted.

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