On Fri, Apr 07, 2017 at 11:52:27AM +0200, Hannes Reinecke wrote: > On 04/07/2017 11:38 AM, Hannes Reinecke wrote: > > On 04/07/2017 11:34 AM, Ming Lei wrote: > >> On Fri, Apr 07, 2017 at 08:58:58AM +0200, Hannes Reinecke wrote: > >>> When generating bootable VM images certain systems (most notably > >>> s390x) require devices with 4k blocksize. This patch implements > >>> a new flag 'LO_FLAGS_BLOCKSIZE' which will set the physical > >>> blocksize to that of the underlying device, and allow to change > >>> the logical blocksize for up to the physical blocksize. > >> > >> Actually this UAPI flag is only for setting logical block size. > >> > > Hmm? No, we're setting the physical blocksize, too. > > Or am I missing something? > > > >>> > >>> Signed-off-by: Hannes Reinecke <[email protected]> > >>> --- > >>> drivers/block/loop.c | 36 +++++++++++++++++++++++++++++++----- > >>> drivers/block/loop.h | 1 + > >>> include/uapi/linux/loop.h | 3 +++ > >>> 3 files changed, 35 insertions(+), 5 deletions(-) > >>> > >>> diff --git a/drivers/block/loop.c b/drivers/block/loop.c > >>> index 81b3900..f098681 100644 > >>> --- a/drivers/block/loop.c > >>> +++ b/drivers/block/loop.c > >>> @@ -221,7 +221,8 @@ static void __loop_update_dio(struct loop_device *lo, > >>> bool dio) > >>> } > >>> > >>> static int > >>> -figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit) > >>> +figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit, > >>> + loff_t logical_blocksize) > >>> { > >>> loff_t size = get_size(offset, sizelimit, lo->lo_backing_file); > >>> sector_t x = (sector_t)size; > >>> @@ -233,6 +234,12 @@ static void __loop_update_dio(struct loop_device > >>> *lo, bool dio) > >>> lo->lo_offset = offset; > >>> if (lo->lo_sizelimit != sizelimit) > >>> lo->lo_sizelimit = sizelimit; > >>> + if (lo->lo_flags & LO_FLAGS_BLOCKSIZE) { > >>> + lo->lo_logical_blocksize = logical_blocksize; > >>> + blk_queue_physical_block_size(lo->lo_queue, lo->lo_blocksize); > >>> + blk_queue_logical_block_size(lo->lo_queue, > >>> + lo->lo_logical_blocksize); > >>> + } > >> > >> We can move setting physical block size into loop_set_fd(), and set > >> 512 bytes as default logical block size in loop_set_fd() too. > >> > > Okay. > > > After thinking about it some more I'm not sure if I agree with that > reasoning. > > One of the goals of this patchset is to keep compability with existing > installations. > If we move setting the physical blocksize into loop_set_fd() (which > needs to be called before loop_set_status()) the physical blocksize > would always be set. > Which would induce a user-visible change. > > Hence I've formulated my patch to _not_ change the default setup if the > new flag isn't set.
OK, better to not break current users, :-) Thanks, Ming
