Writing journal only in Big Endian format

[Eric Sandeen]

On Nov 29, 2009, at 11:17 PM, Nitin Arora <nitin.arora.del at gmail.com>  
wrote:

> Hello,
>
> We are using XFS (Kernel 2.6.18) and facing a problem.
> When any XFS partition is plugged out from a little endian machine  
> and plugged in to a big endian machine,
> it cannot be mounted and gives the following error.
>
> FAT: utf8 is not a recommended IO charset for FAT filesystems,  
> filesystem will be case sensitive!
>
> FAT: bogus number of FAT structure
>
> VFS: Can't find a valid FAT filesystem on dev sda1.
>
> VFS: Can't find ext3 filesystem on dev sda1.
>
> XFS mounting filesystem sda1
>
> Starting XFS recovery on filesystem: sda1 (logdev: internal)
>
> XFS: dirty log written in incompatible format - can't recover
>
> XFS: log mount/recovery failed: error 5
>
> XFS: log mount failed
>
>

Yep this Is expected for a dirty log, but I think a cleanly unmounted  
filesystem should migrate without problems; is this not the case?

So really the problem should be limited to migrating -dirty-  
filesystems, and the complexity of endian-swapping the journal at  
runtime seems overly expensive for this odd case.

Just unmount before migration....

-Eric
>
> Mounting problem goes away after doing "xfs_repair -L /dev/sdb2"
>
> The problem is that big endian machine cannot recognize the journal  
> which was written in
> little endian format by the little endian machine and once the  
> journal is zerod out it can be mouted.
>
> Now the solution to above problem seems writing journal always in  
> big endian format.
>
> Please suggest me, Is there any design limitation in XFS for this.
> Is it okay and feasible to implement it if yes then please give some  
> pointers so that it can be implemented, under some
> suitable compile time switch.
>
> Thanks in advance...
>
> Regards
> Nitin Arora
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