Date: Fri, 27 May 2005 09:56:21 +0200
From: Jens Axboe <axboe@suse.de>
To: Jeff Garzik <jgarzik@pobox.com>
Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] SATA NCQ support
Message-ID: <20050527075621.GR1435@suse.de>
References: <20050527070353.GL1435@suse.de> <4296CAA8.9060307@pobox.com> <20050527073016.GO1435@suse.de> <4296CE3B.3040504@pobox.com> <20050527074712.GQ1435@suse.de>
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On Fri, May 27 2005, Jens Axboe wrote:
> On Fri, May 27 2005, Jeff Garzik wrote:
> > Jens Axboe wrote:
> > >That is the typical case, ata_qc_new() succeeds but we cannot issue the
> > >command yet. So where do you want this logic placed? You cannot drop the
> > >host_lock in-between, as that could potentially change the situation.
> > 
> > ata_scsi_translate() in libata-scsi.c, in between the call to 
> > ata_scsi_qc_new() and ata_qc_issue().
> > 
> > something like:
> > 
> > 	if (ata_scsi_qc_new() fails ||
> > 	    (depth > 0 && ata_check_non_ncq_cmd()))
> > 		complete SCSI command with 'queue full'
> 
> That is an improvement for SCSI originated commands, I can drop
> ATA_QCFLAG_DEFER then. Will make that change. But what about
> ata_qc_issue() from other places? That is the ugly code, which will hit
> the waiting currently.

Actually, slight "problem" there as well... We need to translate the
SCSI command prior to making this decision, as we may get both NCQ and
non-NCQ commands from that path as well. For now I'll just make the
distinction that fs based SCSI requests are the only NCQ candidates, ok?

-- 
Jens Axboe

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