Subject: Re: Adding B_WRITETHRU -- file system question
To: Jason R Thorpe <>
From: Manuel Bouyer <>
List: tech-kern
Date: 12/04/2001 20:47:47
On Mon, Dec 03, 2001 at 02:23:13PM -0800, Jason R Thorpe wrote:
> Warping back to a conversation I had here some time ago...
> I want to add a flag to struct buf which indicates that an I/O
> transaction is to be done in a "cache write-through" manner.

BTW, is B_ORDERED really used ? I see it's set in bowrite() but I can't
find what uses bowrite.

> This is pretty easy to accomplish, for SCSI at least... Set the
> Force Unit Access bit when you see B_WRITETHRU, and then clear
> B_WRITETHRU when the transfer is finished.

Hum, I'm not sure how to enforce this for IDE. I guess we should just disable
the write cache for IDE disks.

Manuel Bouyer <>