Subject: Re: wd, disk write cache, sync cache, and softdep.
To: Manuel Bouyer <firstname.lastname@example.org>
From: Eric Haszlakiewicz <email@example.com>
Date: 12/17/2004 14:45:04
On Fri, Dec 17, 2004 at 09:09:23PM +0100, Manuel Bouyer wrote:
> 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.
So wouldn't that also cause anything else in the drive's cache to
be written out? (e.g. a B1 sent between A1 and A2) That sounds a lot like a
To only flush A1 and A2 you'd need to tie them to A3 somehow, but to
do that you need to change the upper layers to know to do that, right?