Return-Path: <linux-kernel-owner+w=401wt.eu-S1765177AbZLQRkX@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1765177AbZLQRkX (ORCPT <rfc822;w@1wt.eu>);
	Thu, 17 Dec 2009 12:40:23 -0500
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1765137AbZLQRkT
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Thu, 17 Dec 2009 12:40:19 -0500
Received: from THUNK.ORG ([69.25.196.29]:53512 "EHLO thunker.thunk.org"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1765120AbZLQRkQ (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Thu, 17 Dec 2009 12:40:16 -0500
Date: Thu, 17 Dec 2009 12:39:57 -0500
From: tytso@mit.edu
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Kyle McMartin <kyle@mcmartin.ca>, linux-parisc@vger.kernel.org,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       James.Bottomley@suse.de, hch@infradead.org, linux-arch@vger.kernel.org,
       Jens Axboe <jens.axboe@oracle.com>
Subject: Re: [git patches] xfs and block fixes for virtually indexed arches
Message-ID: <20091217173957.GG2123@thunk.org>
Mail-Followup-To: tytso@mit.edu,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Kyle McMartin <kyle@mcmartin.ca>, linux-parisc@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	James.Bottomley@suse.de, hch@infradead.org,
	linux-arch@vger.kernel.org, Jens Axboe <jens.axboe@oracle.com>
References: <20091216043618.GB9104@hera.kernel.org>
 <20091217132256.GO28962@bombadil.infradead.org>
 <alpine.LFD.2.00.0912170811130.15740@localhost.localdomain>
 <20091217163036.GE2123@thunk.org>
 <alpine.LFD.2.00.0912170839550.15740@localhost.localdomain>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.LFD.2.00.0912170839550.15740@localhost.localdomain>
User-Agent: Mutt/1.5.20 (2009-06-14)
X-SA-Exim-Connect-IP: <locally generated>
X-SA-Exim-Mail-From: tytso@thunk.org
X-SA-Exim-Scanned: No (on thunker.thunk.org); SAEximRunCond expanded to false
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 1074
Lines: 22

On Thu, Dec 17, 2009 at 08:46:33AM -0800, Linus Torvalds wrote:
> kmalloc() memory should be ok. It's backed by "real pages". Doing the DMA 
> translations for such pages is trivial and fundamental.

Sure, but there's some rumors/oral traditions going around that some
block devices want bio address which are page aligned, because they
want to play some kind of refcounting game, and if you pass them a
kmalloc() memory, they will explode in some interesting and
entertaining way.  And it's Weird Shit(tm) (aka iSCSI, AoE) type
drivers, that most of us don't have access to, so just because it
works Just Fine on SATA doesn't mean anything.

And none of this is documented anywhere, which is frustrating as hell.
Just rumors that "if you do this, AoE/iSCSI will corrupt your file
systems".

    	    	    	       		       - Ted
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/