Hi Thorsten, Thanks for the report. I will follow up with stable@ to fix them. Best regards, Song On Wed, May 22, 2019 at 5:26 AM Thorsten Knabe <linux@xxxxxxxxxxxxxxxxx> wrote: > > Hello. > > BUG: RAID6 recovery broken by commit > 4f4fd7c5798bbdd5a03a60f6269cf1177fbd11ef (Linux 5.1.3+) > > Replacing a failed disk of a MD RAID6 array causes file system > corruption and data loss on kernels containing commit > 4f4fd7c5798bbdd5a03a60f6269cf1177fbd11ef. > > Affected kernels: 5.1.3, 5.1.4 possibly others. > Unaffected kernels: 5.1.2 > > OS: Debian stretch amd64 > > Steps to reproduce the BUG: > > 1. Create a new 4-disk RAID6 array, create a file system and mount it: > mdadm /dev/md0 --create -l 6 -n 4 /dev/sd[bcde] > mkfs.ext4 /dev/md0 > mount /dev/md0 /mnt > 2. Store some data (a few GB should be fine) on the RAID6 arrays file > system: > cp -r whatever /mnt > 3. Fail a disk of the RAID6 array and remove it from the array: > mdadm /dev/md0 --fail /dev/sdd > mdadm /dev/md0 --remove /dev/sdd > 4. Drop caches: > echo "3" > /proc/sys/vm/drop_caches > 5. Compare data copied to the RAID6 array in step 2 with its source: > diff -r whatever /mnt/whatever > There should be no differences and no file system errors. > 6. Add a new empty disk to the RAID6 array: > mdadm /dev/md0 --add /dev/sdf > 7. RAID6 recovery should start now, wait for the RAID6 recovery to finish. > 8. Drop caches again: > echo "3" > /proc/sys/vm/drop_caches > 9. Compare data copied to the RAID6 array in step 2 with its source again: > diff -r whatever /mnt/whatever > diff now reports a lot of differences and the kernel log gets filled > with file system errors. For example: > EXT4-fs warning (device md0): ext4_dirent_csum_verify:355: inode > #918549: comm diff: No space for directory leaf checksum. Please run > e2fsck -D. > > Reverting commit 4f4fd7c5798bbdd5a03a60f6269cf1177fbd11ef from kernel > 5.1.4 resolves the issues described above. > > Kind regards > Thorsten > > > -- > ___ > | | / E-Mail: linux@xxxxxxxxxxxxxxxxx > |horsten |/\nabe WWW: http://linux.thorsten-knabe.de >
