Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755903AbbHGHu4 (ORCPT ); Fri, 7 Aug 2015 03:50:56 -0400 Received: from mx2.suse.de ([195.135.220.15]:43624 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755480AbbHGHuz (ORCPT ); Fri, 7 Aug 2015 03:50:55 -0400 Message-ID: <55C4635D.8060505@suse.de> Date: Fri, 07 Aug 2015 09:50:53 +0200 From: Hannes Reinecke User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Ming Lei , Christoph Hellwig CC: Jens Axboe , Alexander Graf , Linux Kernel Mailing List Subject: Re: [PATCH 0/4] loop: enable different physical blocksizes References: <1437118027-94602-1-git-send-email-hare@suse.de> <20150807073330.GB17618@lst.de> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2089 Lines: 45 On 08/07/2015 09:44 AM, Ming Lei wrote: > On Fri, Aug 7, 2015 at 3:33 AM, Christoph Hellwig wrote: >> On Mon, Jul 27, 2015 at 06:40:57AM -0400, Ming Lei wrote: >>> On Fri, Jul 17, 2015 at 3:27 AM, Hannes Reinecke wrote: >>>> Currently the loop driver just simulates 512-byte blocks. When >>>> creating images for virtual machines it might be required to use >>>> a different physical blocksize (eg 4k for S/390 DASD). >>> >>> Looks 'qemu-img create' doesn't have parameter of block size, >>> so could you share your use case? And I am just curious why >>> 512-byte can't work for this case. >> >> The use case is to suppot 4k sectors sizes such as DASDs usually provide, >> or just to create a 4k block device to check your filesystem of choice >> handles 4k sectors just fine. Replace 4k with other sector sizes of >> your choice for added benefit. In addition to the DASD use case it's really a >> very useful debugging tool. > > There shouldn't be any problem about looping over DASP which has > 4k sector size. Also for debugging purpose, we can easily emulate 4k > sector size disk by QEMU/virtio-blk. > > We can support 4k sector size on loop for debugging purpose too, but > the side effect is that some images can't be loop mounted any more > after its secror size is become larger, then people might complain that. > Which is why I made it optional, and having to use some ioctl fields to enable this feature. So _if_ someone uses these new features _and_ then complains that the sector size is different I'll have only limited compassion. Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg) -- 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/