Re: [gentoo-dev] gentoo-sources-r9 kernel sources vs. XFS patch

[Seth Mos]

At 04:12 24-10-2002 -0500, John Newman wrote:
>Why is it that the XFS patches from SGI (available at
>ftp://oss.sgi.com/projects/xfs/download/patches/2.4.19) will not patch
>properly against the gentoo-sources kernel 2.4.19-gentoo-r2?  90% of the
>patch goes through but several hunks do fail.  Which patch already in
>2.4.19-gentoo-r2 is incompatible with XFS?

The most recent XFS CVS should work with preempt but it is not thoroughly 
tested. A number  of users have corrupted filesystems when they were 
running with preempt. Both with clean shutdowns and reboots as well as 
"power failures".

I suggest not using preempt with XFS for production systems.

>A related question - why does the gentoo XFS-sources kernel source package
>not come with the preempt-ac patch?  Is preempt incompatible with XFS?

For some reason or the other they had problems with XFS and power failures 
which they were not able to resolve. Most likely this had to do with the 
bad preempt patches interaction.

Note that one of the biggest problems people have had to date is with IDE 
disks that have had the write cache turned on. No filesystem out there can 
recover from a power failure on a disk with write caching turned on. In 
special journaling filesystems have problems with respect to this problem 
since there is _NO_ guarantee that the LOG was actually _written_ to disk 
when the call returns from the block layer. And disastrous things happen 
when the journal/log is corrupt.

The other problem is that some IDE disks are lying about whether the write 
cache is actually turned off.

Otherwise it's a fine filesystem that works just like the others. I have 
had little problems with it to date. I have used it in production for over 
a year.

Cheers

--
Seth
It might just be your lucky day, if you only knew.