Re: JFYI: ext4 bug triggerable by kvm

Christoph Hellwig
2010-08-17T15:04:57Z

On Tue, Aug 17, 2010 at 05:59:07PM +0300, Avi Kivity wrote:
> I agree, but there's another case: tell the guest that we have a
> write cache, use O_DSYNC, but only flush the disk cache on guest
> flushes.

O_DSYNC flushes the disk write cache and any filesystem that supports
non-volatile cache. The disk cache is not an abstraction
exposed to applications.

> I believe this can be approximated by mounting the host filesystem
> with barrier=0?

Mounting the host filesystem with nobarrier means we will never explicit
flush the volatile write cache on the disk.