On 08/07/2015 09:44 AM, Ming Lei wrote: > On Fri, Aug 7, 2015 at 3:33 AM, Christoph Hellwig <[email protected]> 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 <[email protected]> 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 [email protected] +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 [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
