XFS Kernel Panics in CentOS

[Stefan Ring]

> It turned out in my case to be related to:
> http://oss.sgi.com/bugzilla/show_bug.cgi?id=840
>
> Write barriers were not passed when using LVM/XFS/MegaRAID combined. After
> upgrading the kernel to 2.6.39 (used packages from
> http://elrepo.org/tiki/tiki-index.php) all XFS issues were resolved. The
> other solution was not using LVM.

I fail to see how missing write barriers can make a difference to what
the filesystem reads from the block layer. How is this possible? Does
the block layer not take the pending writes into account when handling
read requests?