Kernel ext4 chokes at 8TB on ARM5

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Kernel ext4 chokes at 8TB on ARM5

Postby Sergeanter » Mon Jan 23, 2017 5:44 am

This bug has been fixed by moonman in kernel 4.10.12-2

Just saying. I have posted this bug in two other sub forums but apparently there is not enough people using large disks with ARM5 to care about this.
Ext4 of the current kernel fails to read beyond 8TB. As a result, fsck at boot fails and large RAID does not mount.

EDIT:
I began rolling back rootfs to check kernel, mdadm and e2fsprogs starting September 2016.

EDIT 04/02/17
Something got broken when upgrading kernel from 4.8.1-1 to 4.8.4-1
linux-kirkwood-dt-4.8.1-1 does not have the issue.
linux-kirkwood-dt-4.8.4-1 causes block address overflow
the bug remains now in 4.10.6


Last edited by Sergeanter on Tue Apr 25, 2017 10:38 pm, edited 13 times in total.
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Re: Kernel ext4 chokes at 8TB on ARM5

Postby graysky » Mon Jan 23, 2017 7:19 am

ARM5 = linux-4.4.3-1? If so, this is LTS, so report upstream.
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Re: Kernel ext4 chokes at 8TB on ARM5

Postby WarheadsSE » Mon Jan 23, 2017 3:14 pm

Have you tried this with a pure i686 version of Arch Linux? It's possible that you're surpassing the upper limit of what the 32-bit ARMv5* architecture can logically handle.
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Re: Kernel ext4 chokes at 8TB on ARM5

Postby Sergeanter » Mon Jan 23, 2017 6:02 pm

I will try a 32bit version of linux on PC tonight but should not the block address be architecture independent as in
long long ext4_fsblk_t ?
The block address it chokes on is just above 2^31 so this is not the address per se overflowing but a result of some operation on it.

It would sort of defeat the purpose of advertising those humongous system sizes with ext4 if some architecture supporting ext4 fails to support this.
I see this for example, Armada 370 based ReadyNAS RN104. As far as I know this is a 32bit ARMv7.
http://www.downloads.netgear.com/files/GDC/datasheet/en/RN100.pdf
Single volume size limit: 16TB

I have not had this problem until November I believe, I run this RAID for a couple of years already. Let me see if I have an SD card with older kernel .
I have updated to the latest 4.9.3-1-ARCH but this has been going on for a while.
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Re: Kernel ext4 chokes at 8TB on ARM5

Postby moonman » Tue Jan 24, 2017 1:17 am

I have a 4TB drive working with no issues. Maybe it is something in the raid subsystem. I would ask on kernel mailing list
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Re: Kernel ext4 chokes at 8TB on ARM5

Postby Sergeanter » Tue Jan 24, 2017 2:11 am

I have run scrub repeatedly with no issues. Also, I tried to roll mdadm and e2fsprogs as far back revision wise as possible, it makes no difference.
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Re: Kernel ext4 chokes at 8TB on ARM5

Postby Sergeanter » Wed Jan 25, 2017 8:13 am

I have checked the array with Ubuntu server 32 bit kernel version 4.8.0-22-generic. It passed with no errors . I cannot find an i686 only live CD of Arch linux. I dont know if this is helpful . You would probably want to check Arch specific i686 build.
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Re: Kernel ext4 chokes at 8TB on ARM5

Postby moonman » Wed Jan 25, 2017 2:26 pm

ArchLinux iso contains both 32 and 64 bit bits. You choose which one you want during boot. And you don't have to use Arch, it doesn't really matter.
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Re: Kernel ext4 chokes at 8TB on ARM5

Postby Sergeanter » Wed Jan 25, 2017 4:49 pm

I do not have a 32 bit PC with ESATA so I have to run it on a fairly new 64 bit one with UEFI. Archlinux live USB chooses the architecture automatically during boot and there is no menu as far as I know. But again, 32 bit architecture does not seem to present a problem.
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