Re: [PATCH v2 2/2] nbd: Add testsuite coverage

[Eric Blake]

On 2/27/20 5:02 PM, Eric Blake wrote:
> * HACKING (Using NBD connections in tests): New section.
> (Writing tests that depend on a certain capability): New capability.
> * testsuite/Makefile.am (check-DEJAGNU): Expose NBD witness.
> * configure.ac (AC_CHECK_PROGS): Check for nbdkit.
> * testsuite/lib/poke-dg.exp (dg-require): Add 'nbd' capability.
> (dg-nbd): New command to spawn nbdkit server.
> (poke_finish): Clean up nbdkit.
> * testsuite/poke.cmd/nbd.pk: New test of '.nbd'.
> * testsuite/poke.pkl/open-3.pk: New test of open("nbd...").
> ---

I forgot to mention in the cover letter: I pushed these two patches to 
the eblake/nbd branch if you want to do early testing.

> +proc dg-nbd { args } {
> +    global poke_commands
> +    global poke_data_files
> +    global poke_nbd_pids
> +    global objdir
> +
> +    if { [llength $args] != 3 } {
> +        error "[lindex $args 0]: invalid arguments"
> +    }
> +    dg-require nbd
> +
> +    set data [lindex $args 1]
> +    set sock [lindex $args 2]
> +    set sockdir "[file dirname $sock]"
> +
> +    if {! [file exists $data]} {
> +        error "[lindex $args 0]: file $data not found"
> +    }
> +
> +    file mkdir $sockdir
> +    if { [lsearch -exact $poke_data_files $sockdir] == -1} {
> +        lappend poke_data_files $sockdir
> +    }
> +
> +    set fh [open "|nbdkit -f -U $sock file $data"]

Now that I've written this, I wonder if it would be nicer to use 
nbdkit's data plugin, rather than the file plugin which forces me to 
create a temporary file.  For example, instead of:

> +/* { dg-data {c*} {0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80} nbddata } */
> +/* { dg-nbd nbddata /tmp/pokenbd.[pid]/sock } */

spawning
 nbdkit -f -U $sock file $data
I'm wondering if it would read better as:

/* { dg-nbd {0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80} 
/tmp/pokenbd.[pid]/sock } */

spawning
 nbdkit -f -U $sock data data=$init
(where the first argument to db-nbd has to satisfy the rules of data= as 
describe in 'man nbdkit-data-plugin') would be an improvement.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
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