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From: Joerg.Schilling@fokus.fraunhofer.de (Joerg Schilling)
To: stern@rowland.harvard.edu, dougg@torque.net
Cc: linux-kernel@vger.kernel.org, jens.axboe@oracle.com,
	James.Bottomley@steeleye.com
Subject: Re: [PATCH] Block layer: separate out queue-oriented ioctls
Date: Sun, 18 Feb 2007 19:27:23 +0100	[thread overview]
Message-ID: <45d89a8b.QpxTpRwQB4A12sQN%Joerg.Schilling@fokus.fraunhofer.de> (raw)
In-Reply-To: <Pine.LNX.4.44L0.0702181124450.6341-100000@netrider.rowland.org>

Alan Stern <stern@rowland.harvard.edu> wrote:

> > Alternatively the SG_GET_RESERVED_SIZE ioctl could be
> > modified to yield no more than max_sectors*512 .
>
> There should be one single ioctl which can be applied uniformly to all
> CD-type devices (in fact, to all devices using a request_queue) to learn
> max_sectors.  This rules out using SG_GET_RESERVED_SIZE.

This has nothing to do with CD-type devices!
It is related to SCSI tansport.

> Furthermore, if you changed SG_GET_RESERVED_SIZE in this way you would 
> only increase the confusion.  The reserved size isn't directly related to 
> the maximum allowed DMA length, and there's no point pretending it is.  
> What if it turns out that the reserved size is smaller than max_sectors?  
> Then you'd force user programs to do I/O in chunks that were smaller than 
> necessary.

It would not increase confusion but reduce confusion because all
programs would later behave correctly without the need to change them.

Jörg

-- 
 EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
       js@cs.tu-berlin.de                (uni)  
       schilling@fokus.fraunhofer.de     (work) Blog: http://schily.blogspot.com/
 URL:  http://cdrecord.berlios.de/old/private/ ftp://ftp.berlios.de/pub/schily

  reply	other threads:[~2007-02-18 18:29 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-16 19:37 Alan Stern
2007-02-17  6:28 ` Jens Axboe
2007-02-17 21:18   ` Joerg Schilling
2007-02-18  3:43   ` Douglas Gilbert
2007-02-18 12:37     ` Joerg Schilling
2007-02-18 16:44     ` Alan Stern
2007-02-18 18:27       ` Joerg Schilling [this message]
2007-02-19 16:06         ` Alan Stern
2007-02-19 16:08           ` Joerg Schilling
2007-02-19 17:06             ` Alan Stern
2007-02-19 22:25               ` Douglas Gilbert
2007-02-20  3:48                 ` Alan Stern
2007-02-20  4:47                   ` Douglas Gilbert
2007-02-20 15:55                     ` Alan Stern
2007-04-26  9:19                 ` Joerg Schilling
2007-04-26 15:04                   ` Alan Stern
2007-04-26 15:08                     ` James Bottomley

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