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Re: [Libguestfs] [libnbd PATCH] nbdsh: Add -b option to simplify h.block_status



On Thu, Sep 12, 2019 at 01:54:20PM -0500, Eric Blake wrote:
> We decided to not request the "base:allocation" context by default (if
> a client wants to use block_status on a different context, then they'd
> have to get any default request out of the way); however, block status
> is useless without at least one meta context.  This adds a convenience
> knob for requesting that, and has the nice benefit of working with the
> --connect command line option (previously, if you wanted to use
> block_status, you could not use --connect, because requesting the meta
> context must happen before the connection).

There's no problem with the patch, but I wonder if it's a good idea to
burn though a single letter option (-b) which might be useful in
future for a more common purpose?  "buffer", "block", "byte" all begin
with "b".

Even a two letter abbreviation is fine however (--ba).

Rich.

>  sh/nbdsh.pod       |  9 +++++++
>  python/nbdsh.py    |  4 +++
>  sh/Makefile.am     |  4 ++-
>  sh/test-context.sh | 62 ++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 78 insertions(+), 1 deletion(-)
>  create mode 100755 sh/test-context.sh
> 
> diff --git a/sh/nbdsh.pod b/sh/nbdsh.pod
> index d7fc315..6c540c7 100644
> --- a/sh/nbdsh.pod
> +++ b/sh/nbdsh.pod
> @@ -56,6 +56,15 @@ __EXAMPLES_HEXDUMP__
> 
>  Display brief command line help and exit.
> 
> +=item B<-b>
> +
> +=item B<--base-allocation>
> +
> +Request the use of the "base:allocation" meta context, which is the
> +most common context used with L<nbd_block_status(3)>.  This is
> +equivalent to calling S<C<h.set_meta_context
> +(nbd.CONTEXT_BASE_ALLOCATION)>> in the shell prior to connecting.
> +
>  =item B<-c> 'COMMAND ...'
> 
>  =item B<--command> 'COMMAND ...'
> diff --git a/python/nbdsh.py b/python/nbdsh.py
> index 319b0f0..00bc6bc 100644
> --- a/python/nbdsh.py
> +++ b/python/nbdsh.py
> @@ -27,6 +27,8 @@ def shell():
>      epilog = '''Please read the nbdsh(1) manual page for full usage.'''
>      parser = argparse.ArgumentParser (prog='nbdsh', description=description,
>                                        epilog=epilog)
> +    parser.add_argument ('-b', '--base-allocation', action='store_true',
> +                         help='request the "base:allocation" meta context')
>      parser.add_argument ('--connect', metavar='URI',
>                           help="connect to NBD URI")
>      parser.add_argument ('-c', '--command', action='append',
> @@ -52,6 +54,8 @@ exit() or Ctrl-D                    # Quit the shell
>  help (nbd)                          # Display documentation
>  '''
> 
> +    if args.base_allocation:
> +        h.add_meta_context (nbd.CONTEXT_BASE_ALLOCATION)
>      if args.connect is not None:
>          h.connect_uri (args.connect)
>      # If there are no -c or --command parameters, go interactive,
> diff --git a/sh/Makefile.am b/sh/Makefile.am
> index 8f70e69..415e241 100644
> --- a/sh/Makefile.am
> +++ b/sh/Makefile.am
> @@ -21,6 +21,7 @@ EXTRA_DIST = \
>  	nbdsh.pod \
>  	examples/LICENSE-FOR-EXAMPLES \
>  	examples/hexdump.sh \
> +	test-context.sh \
>  	test-help.sh \
>  	test-pattern.sh \
>  	test-version.sh \
> @@ -43,7 +44,7 @@ nbdsh.1: nbdsh.pod $(top_builddir)/podwrapper.pl
> 
>  endif HAVE_POD
> 
> -TESTS_ENVIRONMENT = LIBNBD_DEBUG=1 EXP_VERSION=$(VERSION)
> +TESTS_ENVIRONMENT = LIBNBD_DEBUG=1 NBDKIT_DEBUG=1 EXP_VERSION=$(VERSION)
>  LOG_COMPILER = $(top_builddir)/run
>  TESTS = \
>  	test-help.sh \
> @@ -53,6 +54,7 @@ TESTS = \
>  if HAVE_NBDKIT
> 
>  TESTS += \
> +	test-context.sh \
>  	test-pattern.sh \
>  	$(NULL)
> 
> diff --git a/sh/test-context.sh b/sh/test-context.sh
> new file mode 100755
> index 0000000..55f9b53
> --- /dev/null
> +++ b/sh/test-context.sh
> @@ -0,0 +1,62 @@
> +#!/usr/bin/env bash
> +# nbd client library in userspace
> +# Copyright (C) 2019 Red Hat Inc.
> +#
> +# This library is free software; you can redistribute it and/or
> +# modify it under the terms of the GNU Lesser General Public
> +# License as published by the Free Software Foundation; either
> +# version 2 of the License, or (at your option) any later version.
> +#
> +# This library is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +# Lesser General Public License for more details.
> +#
> +# You should have received a copy of the GNU Lesser General Public
> +# License along with this library; if not, write to the Free Software
> +# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> +
> +# Test effects of nbdsh -b
> +fail=0
> +
> +# Without -b, no meta context is requested
> +output=$(nbdkit -U - null --run 'nbdsh \
> +    --connect "nbd+unix://?socket=$unixsocket" \
> +    -c "print (h.can_meta_context (nbd.CONTEXT_BASE_ALLOCATION))" </dev/null')
> +if test "x$output" != xFalse; then
> +    echo "$0: unexpected output: $output"
> +    fail=1
> +fi
> +
> +# With -b (and a server that supports it), meta context works.
> +output=$(nbdkit -U - null --run 'nbdsh \
> +    -b --connect "nbd+unix://?socket=$unixsocket" \
> +    -c "print (h.can_meta_context (nbd.CONTEXT_BASE_ALLOCATION))" </dev/null')
> +if test "x$output" != xTrue; then
> +    echo "$0: unexpected output: $output"
> +    fail=1
> +fi
> +
> +# Again, but with -b after --connect
> +output=$(nbdkit -U - null --run 'nbdsh \
> +    --connect "nbd+unix://?socket=$unixsocket" --base-allocation \
> +    -c "print (h.can_meta_context (nbd.CONTEXT_BASE_ALLOCATION))" </dev/null')
> +if test "x$output" != xTrue; then
> +    echo "$0: unexpected output: $output"
> +    fail=1
> +fi
> +
> +if [[ $(nbdkit --help) =~ --no-sr ]]; then
> +    # meta context depends on server cooperation
> +    output=$(nbdkit -U - --no-sr null --run 'nbdsh \
> +      --connect "nbd+unix://?socket=$unixsocket" --base-allocation \
> +      -c "print (h.can_meta_context (nbd.CONTEXT_BASE_ALLOCATION))" </dev/null')
> +    if test "x$output" != xFalse; then
> +        echo "$0: unexpected output: $output"
> +        fail=1
> +    fi
> +else
> +    echo "$0: nbdkit lacks --no-sr"
> +fi
> +
> +exit $fail
> -- 
> 2.21.0
> 
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