On my Ubuntu Server 12.04 I got this errors (via dmesg):

[ 1104.544121] EXT4-fs error (device md0): ext4_mb_generate_buddy:739: group 10771, 0 clusters in bitmap, 32768 in gd
[ 1104.549227] EXT4-fs error (device md0): ext4_mb_generate_buddy:739: group 10772, 0 clusters in bitmap, 32768 in gd
[ 1151.872640] EXT4-fs error (device md0): ext4_mb_generate_buddy:739: group 10784, 28639 clusters in bitmap, 28640 in gd

I have absolutely no idea why these errors are showing up.

My server configuration:

  • 1 x SATA HDD for the OS
  • 4 x 2TB SATA HDD (device md0): RAID 5 on EXT4

Possible sources of the errors:

  • I (or the system automatically) did a resync, because one SATA cable was damaged.
  • I copied some files from an external hdd with NTFS to the EXT4 Raid system (but this shouldn't be a problem I guess).

I googled, but didn't found a solution. I may try:

  • The command fsck (can't provide link, because of superuser.com spam protection..) to repair something? Maybe it helps...
  • Wait for a solution on this Linux Kernel Bug entry
  • Okay I think the resync and fsck command fixed the problem. The errors do not show up again.
    – malisokan
    Dec 29, 2012 at 10:59

2 Answers 2


You should try umounting the disk and running fsck on it. What does this command show?

cat /proc/mdstat

Your disks should be in sync so you can repair the filesystem.

  • Okay I think the resync and fsck command fixed the problem. The errors do not show up again.
    – malisokan
    Apr 26, 2013 at 12:23
  • Could you please expand on the mdstat matter? I have solved my filesystem error message at my Kali Linux on Raspberry by fscking, but I have no such /proc/mdstat file (well, it is a Raspberry version). Jun 29, 2015 at 21:13
  • 1
    /proc/mdstat is a status file for the mdadm multi-disk-admin package used for managing RAID. Unless you're doing something very un-ordinary, you have no RAID on a raspberry pi, and this doesn't apply. The advice is simply to be sure that the RAID array's data is synced between the drives before attempting a filesystem level repair.
    – superboot
    May 3, 2019 at 20:06
  • 1
    You've second guessed and didn't answer answer the question. The question is what does the message mean, why is it happening. Instead you're telling how to fix it.
    – Eric
    Aug 5, 2019 at 14:31

These messages are due to ext4 detecting a mismatch in the free block count between the ext4 buddy allocator bitmaps and the free block count in the group descriptor. This may be the result of corruption of the bitmaps. In the case of a mismatch, the code will update the group descriptor free block count with the calculated value from the bitmaps to ensure they match going forward. The exact cause of this issue is still under investigation in private Bugzilla, but the cause in remote storage situations appears to be hardware/firmware related in a majority of the cases.

source: https://access.redhat.com/solutions/155873

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