[dm-crypt] Filesystem corruption with LVM's pvmove onto an encrypted volume with LUKS2 and a sector size of 4096

* [dm-crypt] Filesystem corruption with LVM's pvmove onto an encrypted volume with LUKS2 and a sector size of 4096
@ 2019-02-21 12:03 Ingo Franzki
  2019-02-21 13:02 ` Arno Wagner
  2019-02-21 14:04 ` Ondrej Kozina
  0 siblings, 2 replies; 6+ messages in thread
From: Ingo Franzki @ 2019-02-21 12:03 UTC (permalink / raw)
  To: dm-crypt

Hi,

we just encountered an error when using LVM's pvmove command to move the data from an un-encrypted LVM physical volume onto an encrypted volume. 
After the pvmove has completed, the file system on the logical volume that resides on the moved physical volumes is corrupted.

It seems to be related to a sector size of 4096 used with LUKS2. Once I use the default sector size (512) then the problem does not happen.
It happens with LUKS2 and even plain mode, as soon as a sector size of 4096 is used. LUKS1 and the default sector size does not show the problem. 

Not sure if this is a problem in dm-crypt or LVM, or a combination of both.

Here is how to reproduce (note the error messages on the very last command): 

# sudo dd if=/dev/zero of=loopbackfile1.img bs=500M count=1
1+0 records in
1+0 records out
524288000 bytes (524 MB, 500 MiB) copied, 2.32777 s, 225 MB/s

# sudo dd if=/dev/zero of=loopbackfile2.img bs=500M count=1
1+0 records in
1+0 records out
524288000 bytes (524 MB, 500 MiB) copied, 1.89992 s, 276 MB/s

# losetup -fP /root/loopbackfile1.img

# losetup -fP /root/loopbackfile2.img

# pvcreate /dev/loop0
  Physical volume "/dev/loop0" successfully created.

# vgcreate LOOP_VG /dev/loop0
  Volume group "LOOP_VG" successfully created

# lvcreate -L 300MB LOOP_VG -n LV /dev/loop0
  Logical volume "LV" created.

# mkfs.ext4 /dev/mapper/LOOP_VG-LV
mke2fs 1.44.1 (24-Mar-2018)
Discarding device blocks: done
Creating filesystem with 307200 1k blocks and 76912 inodes
Filesystem UUID: 344289a3-e251-4d88-b03d-a71a4be2a8ec
Superblock backups stored on blocks:
        8193, 24577, 40961, 57345, 73729, 204801, 221185

Allocating group tables: done
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done

# mount /dev/mapper/LOOP_VG-LV /mnt

# cryptsetup luksFormat --type luks2 --sector-size 4096 /dev/loop1

WARNING!
========
This will overwrite data on /dev/loop1 irrevocably.

Are you sure? (Type uppercase yes): YES
Enter passphrase for /dev/loop1: loop
Verify passphrase: loop

# cryptsetup luksOpen /dev/loop1 enc-loop
Enter passphrase for /dev/loop1: loop

# pvcreate /dev/mapper/enc-loop
  Physical volume "/dev/mapper/enc-loop" successfully created.

# vgextend LOOP_VG /dev/mapper/enc-loop
  Volume group "LOOP_VG" successfully extended

# pvs
  PV                   VG      Fmt  Attr PSize   PFree
  /dev/loop0           LOOP_VG lvm2 a--  496.00m 196.00m
  /dev/mapper/enc-loop LOOP_VG lvm2 a--  492.00m 492.00m

# pvmove /dev/loop0 /dev/mapper/enc-loop
  /dev/loop0: Moved: 30.67%
  /dev/loop0: Moved: 100.00%

# pvs
  /dev/LOOP_VG/LV: read failed after 0 of 1024 at 0: Invalid argument
  /dev/LOOP_VG/LV: read failed after 0 of 1024 at 314507264: Invalid argument
  /dev/LOOP_VG/LV: read failed after 0 of 1024 at 314564608: Invalid argument
  /dev/LOOP_VG/LV: read failed after 0 of 1024 at 4096: Invalid argument
  PV                   VG      Fmt  Attr PSize   PFree
  /dev/loop0           LOOP_VG lvm2 a--  496.00m 496.00m
  /dev/mapper/enc-loop LOOP_VG lvm2 a--  492.00m 192.00m

In case the filesystem of the logical volume is not mounted at the time of pvmove, it gets corrupted anyway, but you only see errors when trying to mount it.

-- 
Ingo Franzki
eMail: ifranzki@linux.ibm.com  
Tel: ++49 (0)7031-16-4648
Fax: ++49 (0)7031-16-3456
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