[Libguestfs] [PATCH v2] lvm: support lvm2 older than 2.02.107

[Richard W.M. Jones]

On Thu, Jan 28, 2016 at 04:11:30PM +0100, Pino Toscano wrote:
> lvm2 2.02.107 adds the -S/--select option used in lvs to filter out only
> public LVs (see RHBZ#1278878).  To make this work again with versions
> of lvm2 older than that, only on old versions filter out thin layouts
> and compose the resulting device strings ourselves.
> 
> The filtering done is much simplier than what "-S lv_role=public" will
> do, but should be good enough for our need.
> ---
>  daemon/lvm.c | 147 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 136 insertions(+), 11 deletions(-)
> 
> diff --git a/daemon/lvm.c b/daemon/lvm.c
> index 979cf63..8bef4d5 100644
> --- a/daemon/lvm.c
> +++ b/daemon/lvm.c
> @@ -103,6 +103,85 @@ convert_lvm_output (char *out, const char *prefix)
>    return ret.argv;
>  }
>  
> +/* Filter a colon-separated output of
> + *   lvs -o lv_attr,vg_name,lv_name
> + * removing thin layouts, and building the device path as we expect it.
> + *
> + * This is used only when lvm has no -S.
> + */
> +static char **
> +filter_convert_old_lvs_output (char *out)
> +{
> +  char *p, *pend;
> +  DECLARE_STRINGSBUF (ret);
> +
> +  p = out;
> +  while (p) {
> +    size_t len;
> +    char *saveptr;
> +    char *lv_attr, *vg_name, *lv_name;
> +
> +    pend = strchr (p, '\n');	/* Get the next line of output. */
> +    if (pend) {
> +      *pend = '\0';
> +      pend++;
> +    }
> +
> +    while (*p && c_isspace (*p))	/* Skip any leading whitespace. */
> +      p++;
> +
> +    /* Sigh, skip trailing whitespace too.  "pvs", I'm looking at you. */
> +    len = strlen (p)-1;
> +    while (*p && c_isspace (p[len]))
> +      p[len--] = '\0';
> +
> +    if (!*p) {			/* Empty line?  Skip it. */
> +    skip_line:
> +      p = pend;
> +      continue;
> +    }
> +
> +    lv_attr = strtok_r (p, ":", &saveptr);
> +    if (!lv_attr)
> +      goto skip_line;
> +
> +    vg_name = strtok_r (NULL, ":", &saveptr);
> +    if (!vg_name)
> +      goto skip_line;
> +
> +    lv_name = strtok_r (NULL, ":", &saveptr);
> +    if (!lv_name)
> +      goto skip_line;
> +
> +    /* Ignore thin layouts (RHBZ#1278878). */
> +    if (lv_attr[0] == 't')
> +      goto skip_line;
> +
> +    /* Ignore "unknown device" message (RHBZ#1054761). */
> +    if (STRNEQ (p, "unknown device")) {
> +      char buf[256];
> +
> +      snprintf (buf, sizeof buf, "/dev/%s/%s", vg_name, lv_name);
> +      if (add_string (&ret, buf) == -1) {
> +        free (out);
> +        return NULL;
> +      }
> +    }
> +
> +    p = pend;
> +  }
> +
> +  free (out);
> +
> +  if (ret.size > 0)
> +    sort_strings (ret.argv, ret.size);
> +
> +  if (end_stringsbuf (&ret) == -1)
> +    return NULL;
> +
> +  return ret.argv;
> +}
> +
>  char **
>  do_pvs (void)
>  {
> @@ -139,26 +218,72 @@ do_vgs (void)
>    return convert_lvm_output (out, NULL);
>  }
>  
> +/* Check whether lvs has -S to filter its output.
> + * It is available only in lvm2 >= 2.02.107.
> + */
> +static int
> +test_lvs_has_S_opt (void)
> +{
> +  static int result = -1;
> +  if (result != -1)
> +    return result;
> +
> +  CLEANUP_FREE char *out = NULL;
> +  CLEANUP_FREE char *err = NULL;
> +
> +  int r = command (&out, &err, str_lvm, "lvs", "--help", NULL);
> +  if (r == -1) {
> +    reply_with_error ("lvm lvs --help: %s", err);
> +    return -1;
> +  }
> +
> +  if (strstr (out, "-S") == NULL)
> +    result = 0;
> +  else
> +    result = 1;
> +
> +  return result;
> +}
> +
>  char **
>  do_lvs (void)
>  {
>    char *out;
>    CLEANUP_FREE char *err = NULL;
>    int r;
> +  int has_S = test_lvs_has_S_opt ();
>  
> -  r = command (&out, &err,
> -               str_lvm, "lvs",
> -               "-o", "vg_name,lv_name",
> -               "-S", "lv_role=public",
> -               "--noheadings",
> -               "--separator", "/", NULL);
> -  if (r == -1) {
> -    reply_with_error ("%s", err);
> -    free (out);
> +  if (has_S < 0)
>      return NULL;
> -  }
>  
> -  return convert_lvm_output (out, "/dev/");
> +  if (has_S > 0) {
> +    r = command (&out, &err,
> +                 str_lvm, "lvs",
> +                 "-o", "vg_name,lv_name",
> +                 "-S", "lv_role=public",
> +                 "--noheadings",
> +                 "--separator", "/", NULL);
> +    if (r == -1) {
> +      reply_with_error ("%s", err);
> +      free (out);
> +      return NULL;
> +    }
> +
> +    return convert_lvm_output (out, "/dev/");
> +  } else {
> +    r = command (&out, &err,
> +                 str_lvm, "lvs",
> +                 "-o", "lv_attr,vg_name,lv_name",
> +                 "--noheadings",
> +                 "--separator", ":", NULL);
> +    if (r == -1) {
> +      reply_with_error ("%s", err);
> +      free (out);
> +      return NULL;
> +    }
> +
> +    return filter_convert_old_lvs_output (out);
> +  }
>  }

ACK.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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