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3.18.0, ext4 journal_checksum not working anymore?
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Massimo B.
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PostPosted: Sat Jan 10, 2015 6:45 pm    Post subject: 3.18.0, ext4 journal_checksum not working anymore? Reply with quote

Hi,

until last my root partition in fstab was:
Code:
LABEL=root         /         ext4   noatime,nodiratime,nouser_xattr,barrier,data=writeback,journal_checksum,commit=100      0 1

Now the system was not booting anymore because ext4 was not mounted.
It took me some time to get to know, journal_checksum is not working anymore. This is sys-kernel/ck-sources-3.18.0 and sys-fs/e2fsprogs-1.42.12.
Changing fstab it is working again:
Code:
LABEL=root         /         ext4   noatime,nodiratime,nouser_xattr,barrier,data=writeback,commit=100      0 1

Trying to remount:
Code:
mount -o remount,journal_checksum /
Code:
EXT4-fs (sda3): changing journal_checksum during remount not supported

If this is only the case for remount I tried to set it as default:
Code:
$ tune2fs -O metadata_csum /dev/sda3
tune2fs 1.42.12 (29-Aug-2014)
Setting filesystem feature 'metadata_csum' not supported.

I read this is only supported by some branch of the e2fsprogs. But why was journal checksumming working at all before the last updates?
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Hu
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PostPosted: Sat Jan 10, 2015 8:13 pm    Post subject: Reply with quote

For the remount case, ext4: disallow changing journal_csum option during remount (v3.18-rc2-4-g6b992ff) added the message and turned a silent failure into a reported failure.
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mv
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PostPosted: Sun Jan 11, 2015 6:36 am    Post subject: Reply with quote

I have the same problem. So the next question is: How do you force mounting of root partition (and remounting) with the journal_checksum option in
a) openrc
b) systemd
without patching the init-system and without using an initramdisk?
Currently, neither does the first mount according to fstab (of course, not...). systemd tries to force your fstab option on the remount and thus causes total breakage, while openrc remounts ignoring the fstabn options which is not a perfect solution, either.
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kernelOfTruth
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PostPosted: Fri Jan 16, 2015 10:07 pm    Post subject: Reply with quote

does appending flags to the kernel on bootup (grub, linuxrc, syslinux, etc.), e.g.

Code:
rootflags=data=writeback,journal_checksum,commit=100


work ?
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mv
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PostPosted: Sat Jan 17, 2015 7:02 am    Post subject: Reply with quote

kernelOfTruth wrote:
does appending flags to the kernel on bootup work?

Like a charm with both, openrc and systemd :D
Thanks a lot!
I knew about the rootfstype= kernel option, but did not expect that there is such an option for mount flags, too.
Some mount flags are not supported (e.g. I had to remove "defaults", "dev", "suid", "exec", and even "noatime" since the kernel greeted me with a panic). However, "data=ordered,journal_checksum,barrier=1" is accepted and honoured.
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kernelOfTruth
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PostPosted: Sun Jan 18, 2015 2:30 pm    Post subject: Reply with quote

You're welcome :)

it took myself a lot time to find this out back then

a shame that the options from /etc/fstab (or most of them) don't get applied
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mv
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PostPosted: Sun Jan 18, 2015 4:33 pm    Post subject: Reply with quote

kernelOfTruth wrote:
a shame that the options from /etc/fstab (or most of them) don't get applied

Not really: Is the story of Münchhausen and his horse known to you? I mean: How can you apply mount options which you have to read from a file in the filesystem you want to mount?
However, what is a shame is that "remounting" obviously does not mean for ext* what everybody understands from this name: umount and subsequent remount, and thus to remount with any options should not be a problem at all (as long as the filesystem can be mounted with these options at all, of course).
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weedy
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PostPosted: Sat Jan 24, 2015 3:29 am    Post subject: Reply with quote

Thanks for this, just got around to rebooting my laptop and the 3.18 update made my first boot a lot of fun.
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mv
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PostPosted: Sat Jan 24, 2015 5:19 am    Post subject: Reply with quote

weedy wrote:
Thanks for this, just got around to rebooting my laptop and the 3.18 update made my first boot a lot of fun.

I was also angry about this, first. But then I realized that the real reason is that over all those years I ran ext4 without journal_checksum, and even without knowing it.
So once more: The "real" problem is not the new "verbose" refusal but the inability to change options when remounting - which is clearly against the documentation of "mount" and the expectation which the user has.
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