Hi,
I see a strange behaviour when playing with the metadata_csum parameter of ext4.
(I use a Debian Stretch, with a kernel 4.9.0-8-amd64 #1 SMP Debian 4.9.110-3+deb9u6 (2018-10-08) x86_64 GNU/Linux)
How to reproduce :
* I enable metada checksum : OK
root@test# tune2fs -O metadata_csum /dev/my_vol
tune2fs 1.43.4 (31-Jan-2017)
Enabling checksums could take some time.
Proceed anyway (or wait 5 seconds) ? (y,N) y
* I check : Checksum enabled
root@test# tune2fs -l /dev/my_vol
tune2fs 1.43.4 (31-Jan-2017)
Filesystem volume name: <none>
[...]
Journal backup: inode blocks
Checksum type: crc32c
Checksum: 0xb0e3a180
* I change filesystem UUID : OK
root@test# tune2fs -U random /dev/my_vol
tune2fs 1.43.4 (31-Jan-2017)
Setting UUID on a checksummed filesystem could take some time.
Proceed anyway (or wait 5 seconds) ? (y,N) y
* I disable metadata checksum : OK
root@test# tune2fs -O ^metadata_csum /dev/my_vol
tune2fs 1.43.4 (31-Jan-2017)
Disabling checksums could take some time.
Proceed anyway (or wait 5 seconds) ? (y,N) y
* I change filesystem UUID : It looks like metada checksum still is enabled
root@test# tune2fs -U random /dev/my_vol
tune2fs 1.43.4 (31-Jan-2017)
Setting UUID on a checksummed filesystem could take some time.
Proceed anyway (or wait 5 seconds) ? (y,N) y
* I fsck the filesystem to see if it could fix this.
root@test# e2fsck -f /dev/my_vol
2fsck 1.43.4 (31-Jan-2017)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/my_vol: 16303/3932160 files (0.9% non-contiguous), 1829950/15728640 blocks
* I check : metadata checksum looks like disabled
root@test# tune2fs -l /dev/my_vol tune2fs 1.43.4 (31-Jan-2017)
Filesystem volume name: <none>
[...]
Journal backup: inode blocks
* I change filesystem UUID : It looks like metada checksum still is enabled
root@test# tune2fs -U random /dev/my_vol
tune2fs 1.43.4 (31-Jan-2017)
Setting UUID on a checksummed filesystem could take some time.
Proceed anyway (or wait 5 seconds) ? (y,N) y
Is it a bug ?
How can I actually disable this parameter ?
Best regards,
jC Guillain
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