[Libguestfs] [libnbd PATCH] RFC: api: Add set_request_block_size

[Eric Blake]

On Sun, Feb 20, 2022 at 07:14:06PM +0000, Richard W.M. Jones wrote:
> On Thu, Feb 17, 2022 at 05:04:13PM -0600, Eric Blake wrote:
> > WIP: I need to finish writing the actual interop-qemu-block-size.sh to
> > demonstrate scenarios where qemu-nbd advertises a block size > 1 to
> > clients that request it, but sticks to 1 otherwise (see
> > https://gitlab.com/qemu-project/qemu/-/blob/master/nbd/server.c#L660).
> > 
> > Our testsuite coverage of nbd_get_block_size() is pretty sparse (a
> > single line in tests/errors.c, which was skipping until patches to
> > nbdkit finally made it possible to utilize).  But in the process of
> > adding an interop test with qemu-nbd, I also noticed that qemu-nbd (at
> > least version 6.2) exposes different block sizes to older clients that
> > don't request block size than it does to newer clients which promise
> > to obey block sizes.  We still want to request by default, but now we
> > need a knob, similar to the existing set_full_info(), for overriding
> > that default for testing purposes.
> 
> The idea seems sensible.

Okay, I'll polish it up with a complete test with another post later
today.

> 
> > @@ -20,6 +20,7 @@ include $(top_srcdir)/subdir-rules.mk
> >  EXTRA_DIST = \
> >  	dirty-bitmap.sh \
> >  	interop-qemu-storage-daemon.sh \
> > +  interop-qemu-block-size.sh \
> >  	list-exports-nbd-config \
> >  	list-exports-test-dir/disk1 \
> >  	list-exports-test-dir/disk2 \
> > @@ -141,6 +142,7 @@ TESTS += \
> >  	socket-activation-qemu-nbd \
> >  	dirty-bitmap.sh \
> >  	structured-read.sh \
> > +  interop-qemu-block-size.sh \
> >  	$(NULL)
> 
> Is there an issue with the whitespace on these lines?

The recent addition of .editorconfig is causing this, and this is the
second time I've been hit by it.  For some reason, emacs is now
preferring the addition of 2 spaces rather than a TAB character,
because the config is telling it to prefer showing TABs with a width
of 2 spaces when editing .mk files.  I will fix this instance as part
of finalizing the test and posting v2, but I have no idea how to
further tweak .editorconfig to not have emacs make the mistake in the
first place.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org