Here is how to reproduce it. It happens during fstrim. I found other occurrences of the error in the mailing list, but they were not related to trim so they may be something different. modprobe scsi_debug dev_size_mb=256 lbpws=1 dd if=/dev/zero of=/dev/sdb bs=1M fdisk /dev/sdb >> create a new partition accepting all defaults fdisk -lu /dev/sdb|tail -1 >> should show: /dev/sdb1 57 524285 262114+ 83 Linux mkfs.ext4 /dev/sdb1 mkdir test mount /dev/sdb1 test fstrim ./test Here is the output in dmesg: [140934.644166] EXT4-fs (sdb1): mounted filesystem with ordered data mode. Opts: (null) [140941.562060] EXT4-fs error (device sdb1): ext4_mb_generate_buddy:741: group 16, 8160 clusters in bitmap, 4064 in gd [140941.603066] EXT4-fs error (device sdb1): ext4_mb_generate_buddy:741: group 25, 8192 clusters in bitmap, 7934 in gd [140941.613060] EXT4-fs error (device sdb1): ext4_mb_generate_buddy:741: group 27, 8192 clusters in bitmap, 7934 in gd [140941.634074] EXT4-fs error (device sdb1): ext4_mb_generate_buddy:741: group 31, 8192 clusters in bitmap, 8159 in gd Hope this helps, Paolo -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html