Re: [Libguestfs] [PATCH nbdkit 6/7] cache: Add cache-min-block-size parameter

On Wed, Aug 04, 2021 at 10:47:34AM +0200, Martin Kletzander wrote: > >+# Run nbdkit with the caching filter. > >+start_nbdkit -P cache-block-size.pid -U $sock --filter=cache \ > >+ file cache-block-size.img cache-min-block-size=64K > >+ > >+nbdsh --connect "nbd+unix://?socket=$sock" \ > >+ -c ' > >+# Write some pattern data to the overlay and check it reads back OK. > >+buf = b"abcd" * 16384 > >+h.pwrite(buf, 32768) > >+zero = h.pread(32768, 0) > >+assert zero == bytearray(32768) > >+buf2 = h.pread(65536, 32768) > >+assert buf == buf2 > >+ > >+# Flushing should write through to the underlying file. > >+h.flush() > >+ > >+with open("cache-block-size.img", "rb") as file: > >+ zero = file.read(32768) > >+ assert zero == bytearray(32768) > >+ buf2 = file.read(65536) > >+ assert buf == buf2 > >+' > > > I do not see how this checks that the min block size is respected. I > would expect something along the lines of: > > 1) read 32k > 2) write to the underlying file past those 32k > 3) read another 32k (from offset == 32k) > 4) check that the last read returned original data and not those written > in step 2) Yes this test is not great. I think it was basically copied from this one: https://gitlab.com/nbdkit/nbdkit/-/blob/master/tests/test-cache.sh I'll see if I can rethink this once I've got the v2v stuff out of the way unless someone else comes up with a fix.

Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-top is 'top' for virtual machines. Tiny program with many powerful monitoring features, net stats, disk stats, logging, etc. http://people.redhat.com/~rjones/virt-top