On 08/18/2017 08:15 AM, Omar Sandoval wrote: > From: Omar Sandoval <osandov@xxxxxx> > > When I was writing a test for the new loop device block size > functionality, I realized that the interface is kind of dumb: > > - lo_init[0] is never filled in with the logical block size we > previously set > - lo_flags returned from LOOP_GET_STATUS will have LO_FLAGS_BLOCKSIZE > set if we previously called LOOP_SET_STATUS with LO_FLAGS_BLOCKSIZE > set, which doesn't really mean anything > > Instead, for LOOP_GET_STATUS, let's always fill in lo_init[0] and set > the LO_FLAGS_BLOCKSIZE flag to indicate we support it. > > Signed-off-by: Omar Sandoval <osandov@xxxxxx> > --- > drivers/block/loop.c | 33 +++++++++++++++++---------------- > 1 file changed, 17 insertions(+), 16 deletions(-) > Phew. 'Dumb interface'. 'tis wasn't me who designed the interface; Backwards compability are the watchwords here. Personally, I would have loved to design a new interface. I've got quite some flak for daring to break existing interfaces, most notably setting logical and physical blocksize per default (which I would _love_ to have done, seeing that it really makes sense here). But as this would change the behaviour I've gone through pains (and several _years_ of iterations) to get this sorted. So if you design a blocktest for that ensure that a) the sysfs attributes before and after the patch are _identical_ b) the sysfs attributes will only change if the 'LO_FLAGS_BLOCKSIZE' flag has been set and c) validate the written blocksizes; this is required to be able to install bootloaders there This whole interface was designed such that you can prepare bootable diskimages for S/390 DASDs, which use a native 4k blocksize. Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking hare@xxxxxxx +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)
