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Date: Mon, 11 Mar 2002 11:34:46 +0000
From: "Stephen C. Tweedie" <sct@redhat.com>
To: Douglas Gilbert <dougg@torque.net>
Cc: "Stephen C. Tweedie" <sct@redhat.com>,
        Jeremy Higdon <jeremy@classic.engr.sgi.com>,
        Daniel Phillips <phillips@bonn-fries.net>,
        James Bottomley <James.Bottomley@SteelEye.com>,
        Chris Mason <mason@suse.com>, linux-kernel@vger.kernel.org,
        linux-scsi@vger.kernel.org
Subject: Re: [PATCH] 2.4.x write barriers (updated for ext3)
Message-ID: <20020311113446.A10150@redhat.com>
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In-Reply-To: <3C8AEDFC.502CAD04@torque.net>; from dougg@torque.net on Sun, Mar 10, 2002 at 12:24:12AM -0500
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Hi,

On Sun, Mar 10, 2002 at 12:24:12AM -0500, Douglas Gilbert wrote:

> > FUA is not available on WRITE6, only WRITE10 or WRITE12 commands.
> 
> Stephen,
> FUA is also available on WRITE16.

I said WRITE6, not WRITE16. :-)  WRITE6 uses the low 5 bits of the LUN
byte for the top bits of the block number; WRITE10 and later use those
5 bits for DPO/FUA etc.  But WRITE6 is a horribly limited interface:
you only have 21 bits of block number for a start, so it's limited to
1GB on 512-byte-sector devices.  We can probably ignore WRITE6 safely
enough.

--Stephen
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