Re: [Libguestfs] [libnbd PATCH] info: Add support for new 'qemu-nbd -A' qemu:allocation-depth

["Richard W.M. Jones" <rjones@redhat.com>]

On Tue, Oct 27, 2020 at 10:33:48AM -0500, Eric Blake wrote:
> On 10/16/20 10:23 AM, Eric Blake wrote:
> > A rather trivial decoding; we may enhance it further if qemu extends
> > things to give an integer depth alongside its tri-state encoding.
> > ---
> > 
> > I'll wait to push this to libnbd until the counterpart qemu patches
> > land upstream, although it looks like I've got positive review.
> 
> Whoops, I accidentally pushed this before qemu stuff landed upstream,
> and in the meantime, we changed our minds on what to expose over
> qemu:allocation-depth to be a bare integer rather than a tri-state.
> I'll push this followup (but this time, wait for the actual qemu patch
> to land).  In fact, I should probably add test-suite coverage...

ACK.  I have a patch which touches this file but it's a simple merge
to combine the two changes.

Rich.

> >From eba8734654e6fd340e18b3e07c3213ed1a0ab9e8 Mon Sep 17 00:00:00 2001
> From: Eric Blake <eblake@redhat.com>
> Date: Tue, 27 Oct 2020 10:27:25 -0500
> Subject: [libnbd PATCH] info: Adjust to actual 'qemu-nbd -A' semantics
> 
> Review on the qemu list has led to an altered definition of what
> 'qemu:allocation-depth' should report: rather than a tri-state value,
> it is an actual depth.  It's time to match what actually got committed
> into qemu, which in turn means a slight refactoring to use a malloc'd
> string for a description.
> 
> Fixes: 71455c021
> ---
>  info/nbdinfo.c | 27 +++++++++++++++------------
>  1 file changed, 15 insertions(+), 12 deletions(-)
> 
> diff --git a/info/nbdinfo.c b/info/nbdinfo.c
> index 2b22f51..b152f28 100644
> --- a/info/nbdinfo.c
> +++ b/info/nbdinfo.c
> @@ -767,28 +767,30 @@ get_content (struct nbd_handle *nbd, int64_t size)
>  }
> 
>  /* Callback handling --map. */
> -static const char *
> +static char *
>  extent_description (const char *metacontext, uint32_t type)
>  {
> +  char *ret;
> +
>    if (strcmp (metacontext, "base:allocation") == 0) {
>      switch (type) {
> -    case 0: return "allocated";
> -    case 1: return "hole";
> -    case 2: return "zero";
> -    case 3: return "hole,zero";
> +    case 0: return strdup ("allocated");
> +    case 1: return strdup ("hole");
> +    case 2: return strdup ("zero");
> +    case 3: return strdup ("hole,zero");
>      }
>    }
>    else if (strncmp (metacontext, "qemu:dirty-bitmap:", 18) == 0) {
>      switch (type) {
> -    case 0: return "clean";
> -    case 1: return "dirty";
> +    case 0: return strdup ("clean");
> +    case 1: return strdup ("dirty");
>      }
>    }
>    else if (strcmp (metacontext, "qemu:allocation-depth") == 0) {
> -    switch (type & 3) {
> -    case 0: return "unallocated";
> -    case 1: return "local";
> -    case 2: return "backing";
> +    switch (type) {
> +    case 0: return strdup ("unallocated");
> +    case 1: return strdup ("local");
> +    case 2: asprintf (&ret, "backing depth %d", type); return ret;
>      }
>    }
> 
> @@ -810,7 +812,7 @@ extent_callback (void *user_data, const char
> *metacontext,
> 
>    /* Print the entries received. */
>    for (i = 0; i < nr_entries; i += 2) {
> -    const char *descr = extent_description (map, entries[i+1]);
> +    char *descr = extent_description (map, entries[i+1]);
> 
>      if (!json_output) {
>        fprintf (fp, "%10" PRIu64 "  "
> @@ -837,6 +839,7 @@ extent_callback (void *user_data, const char
> *metacontext,
>        comma = true;
>      }
> 
> +    free (descr);
>      offset += entries[i];
>    }
> 
> -- 
> 2.29.0
> 
> 
> 
> -- 
> Eric Blake, Principal Software Engineer
> Red Hat, Inc.           +1-919-301-3226
> Virtualization:  qemu.org | libvirt.org
> 
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-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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