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Message-ID: <20090423063542.GK4593@kernel.dk>
Date: Thu, 23 Apr 2009 08:35:42 +0200
From: Jens Axboe <jens.axboe@...cle.com>
To: Jeff Garzik <jeff@...zik.org>
Cc: linux-ide@...r.kernel.org, linux-scsi@...r.kernel.org,
LKML <linux-kernel@...r.kernel.org>, Tejun Heo <htejun@...il.com>
Subject: Re: [PATCH] libata: rewrite SCSI host scheme to be one per ATA host
On Wed, Apr 22 2009, Jeff Garzik wrote:
> Jeff Garzik wrote:
>> Currently, libata creates a Scsi_Host per port. This was originally
>> done to leverage SCSI's infrastructure to arbitrate among master/slave
>> devices, but is not needed for most modern SATA controllers. And I
>> _think_ it is not needed for master/slave if done properly, either.
>
> BTW note the above, with regards to the libata SCSI->block conversion.
> libata currently relies on SCSI for some amount of generic device
> arbitration, in several situations (see ->qc_defer,
> SCSI_MLQUEUE_.*_BUSY). libata expects SCSI to be intelligent and not
> starve devices, etc.
Defer looks like internal policy, I don't see that functioning any
different in the block layer. SCSI_MLQUEUE_*_BUSY in SCSI is primarily
using the block layer functionality of BLKPREP_DEFER to begin with, so I
think we're pretty close to providing all that already.
--
Jens Axboe
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