Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757792Ab3HHMRz (ORCPT ); Thu, 8 Aug 2013 08:17:55 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:47896 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756141Ab3HHMRx (ORCPT ); Thu, 8 Aug 2013 08:17:53 -0400 Date: Thu, 8 Aug 2013 05:17:47 -0700 From: Christoph Hellwig To: "Dilger, Andreas" Cc: Christoph Hellwig , Xiong Zhou , Greg Kroah-Hartman , Peng Tao , Paul Bolle , Jiri Kosina , "linux-kernel@vger.kernel.org" , "devel@driverdev.osuosl.org" Subject: Re: [PATCH v2] staging/lustre: lloop depends on BLOCK Message-ID: <20130808121747.GA5372@infradead.org> References: <20130802104930.GB1718@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1198 Lines: 28 On Wed, Aug 07, 2013 at 07:45:17AM +0000, Dilger, Andreas wrote: > The problem still remains that the kernel loop driver eventually depends on > a local block device for the pages/bios to be written. The Lustre lloop > driver bypasses the VFS and block layer to generate RPCs from the submitted > pages to RDMA over the network without a data copy. No, it doesn't. It still consumes bios just like the regular loop driver. Besides missing all kinds of fixes from years of kernel development the only difference is that it takes a lustre-specific shortcut into the direct I/O code instead of going through the pagecache. The patch series I've pointed you to does exactly that in a generic way and thus superceeds the lloop driver fully. In case my previous reference was a bit to vague the series starts at: [PATCH V8 00/33] loop: Issue O_DIRECT aio using bio_vec please take a look and make sure to review it in case you see any shortcomings. -- 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/