[dm-devel] Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md.

[Jens Axboe <jens axboe oracle com>]

On Thu, May 31 2007, Phillip Susi wrote:
> David Chinner wrote:
> >That sounds like a good idea - we can leave the existing
> >WRITE_BARRIER behaviour unchanged and introduce a new WRITE_ORDERED
> >behaviour that only guarantees ordering. The filesystem can then
> >choose which to use where appropriate....
> 
> So what if you want a synchronous write, but DON'T care about the order? 
>   They need to be two completely different flags which you can choose 
> to combine, or use individually.

If you have a use case for that, we can easily support it as well...
Depending on the drive capabilities (FUA support or not), it may be
nearly as slow as a "real" barrier write.

-- 
Jens Axboe