Hi,
I'm writing a backup script that images a btrfs using btrfs-image,
then restores to a file on a loop device. Since I had trouble mounting
the original and copied btrfs filesystems with the same UUID on the
same machine, I decided to try btrfstune -fu. However, this appears to
corrupt the copied filesystem altogether making fsck and mount fail.
Details below.
Is this a bug?
$ uname -a
Linux adventure 3.16.0-67-generic #87~14.04.1-Ubuntu SMP Fri Mar 11
00:26:02 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
$ btrfs --version
btrfs-progs v4.4
$ btrfstune -fu /dev/loop2
Current fsid: 36012b08-1e33-4d3c-ac23-5ccffd3295cd
New fsid: 8f70d0af-8ffa-4c82-a817-941e6abfaf9a
Set superblock flag CHANGING_FSID
Change fsid in extents
Change fsid on devices
Clear superblock flag CHANGING_FSID
Fsid change finished
$ btrfs check /dev/loop2
fsid mismatch, want=36012b08-1e33-4d3c-ac23-5ccffd3295cd,
have=8f70d0af-8ffa-4c82-a817-941e6abfaf9a
Couldn't read chunk root
Couldn't open file system
$ echo $?
251
$ mount /dev/loop2 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/loop2,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
$ echo $?
32
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