Subject: Re: wd, disk write cache, sync cache, and softdep.
To: Eric Haszlakiewicz <>
From: Manuel Bouyer <>
List: tech-kern
Date: 12/17/2004 21:09:23
On Fri, Dec 17, 2004 at 01:56:46PM -0600, Eric Haszlakiewicz wrote:
> 	How can it know A1 is done if there's no way to tell the drive to
> flush its cache?  A possible timeline I see is:
> send A1, drive says OK,
> send A2, drive says OK,
> send A3+FUA, drive writes A3 (due to FUA), drive says OK,
> drive writes A2, drive writes A1

If you issue A3 with an "ordered queue tag", then the FUA on A3 will force A1
and A2 before A3. But you can still have A2, A1, A3.

Manuel Bouyer <>
     NetBSD: 26 ans d'experience feront toujours la difference