Re: [Libguestfs] [PATCH 2/8] New API: btrfs_subvolume_show

Richard W.M. Jones
Fri, 05 Dec 2014 12:30:52 -0000

On Tue, Dec 02, 2014 at 05:33:32PM +0800, Hu Tao wrote:
> btrfs_subvolume_show shows the detailed information of a subvolume or
> snapshot.
>
> Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> ---
>  daemon/btrfs.c       | 185
+++++++++++++++++++++++++++++++++++++++++++++++++++
>  generator/actions.ml |   9 +++
>  src/MAX_PROC_NR      |   2 +-
>  3 files changed, 195 insertions(+), 1 deletion(-)
>
> diff --git a/daemon/btrfs.c b/daemon/btrfs.c
> index 471cfbd..2cfb364 100644
> --- a/daemon/btrfs.c
> +++ b/daemon/btrfs.c
> @@ -24,11 +24,13 @@
>  #include <pcre.h>
>  #include <string.h>
>  #include <unistd.h>
> +#include <assert.h>
>
>  #include "daemon.h"
>  #include "actions.h"
>  #include "optgroups.h"
>  #include "xstrtol.h"
> +#include "c-ctype.h"
>
>  GUESTFSD_EXT_CMD(str_btrfs, btrfs);
>  GUESTFSD_EXT_CMD(str_btrfstune, btrfstune);
> @@ -810,3 +812,186 @@ do_btrfs_fsck (const char *device, int64_t
superblock, int repair)
>
>    return 0;
>  }

Ugh.  'btrfs' should have more easily parsable output.

> +/* analyze_line: analyze one line contains key:value pair.
> + * returns the next position following \n.
> + */
> +static char *analyze_line (char *line, char **key, char **value)

Can you put the function name on a new line, so:

static char *
analyze_line (char *line, char **key, char **value)

The reason for this is to allow you to easily grep function
declarations in the source:

git grep ^analyze_line

> +{
> +  char *p = line;
> +  char *next = NULL;
> +  char delimiter = ':';
> +  char *del_pos = NULL;
> +
> +  if (!line || *line == '\0') {
> +    *key = NULL;
> +    *value = NULL;
> +    return NULL;
> +  }
> +
> +  next = strchr (p, '\n');
> +  if (next) {
> +    *next = '\0';
> +    ++next;
> +  }
> +
> +  /* leading spaces and tabs */
> +  while (*p && c_isspace (*p))
> +    ++p;
> +
> +  assert (key);
> +  if (*p == delimiter)
> +    *key = NULL;
> +  else
> +    *key = p;
> +
> +  del_pos = strchr (p, delimiter);
> +  if (del_pos) {
> +    *del_pos = '\0';
> +
> +    /* leading spaces and tabs */
> +    do {
> +      ++del_pos;
> +    } while (*del_pos && c_isspace (*del_pos));
> +    assert (value);
> +    *value = del_pos;
> +  } else
> +    *value = NULL;
> +
> +  return next;
> +}

> +char **do_btrfs_subvolume_show (const char *subvolume)
> +{
> +  const size_t MAX_ARGS = 64;
> +  const char *argv[MAX_ARGS];
> +  size_t i = 0;
> +  CLEANUP_FREE char *subvolume_buf = NULL;
> +  CLEANUP_FREE char *err = NULL;
> +  CLEANUP_FREE char *out = NULL;
> +  char *p, *key = NULL, *value = NULL;
> +  DECLARE_STRINGSBUF (ret);
> +  int r;
> +
> +  subvolume_buf = sysroot_path (subvolume);
> +  if (subvolume_buf == NULL) {
> +    reply_with_perror ("malloc");
> +    return NULL;
> +  }
> +
> +  ADD_ARG (argv, i, str_btrfs);
> +  ADD_ARG (argv, i, "subvolume");
> +  ADD_ARG (argv, i, "show");
> +  ADD_ARG (argv, i, subvolume_buf);
> +  ADD_ARG (argv, i, NULL);
> +
> +  r = commandv (&out, &err, argv);
> +  if (r == -1) {
> +    reply_with_error ("%s: %s", subvolume, err);
> +    return NULL;
> +  }
> +
> +  /* Output is:
> +   *
> +   * /
> +   *         Name:                   root
> +   *         uuid:                   c875169e-cf4e-a04d-9959-b667dec36234
> +   *         Parent uuid:            -
> +   *         Creation time:          2014-11-13 10:13:08
> +   *         Object ID:              256
> +   *         Generation (Gen):       6579
> +   *         Gen at creation:        5
> +   *         Parent:                 5
> +   *         Top Level:              5
> +   *         Flags:                  -
> +   *         Snapshot(s):
> +   *                                 snapshots/test1
> +   *                                 snapshots/test2
> +   *                                 snapshots/test3
> +   *
> +   */
> +  p = analyze_line(out, &key, &value);
> +  if (!p) {
> +    reply_with_error ("truncated output: %s", out);
> +    return NULL;
> +  }
> +
> +  /* If the path is the btrfs root, `btrfs subvolume show' reports:
> +   *   <path> is btrfs root
> +   */
> +  if (strstr (key, "is btrfs root") != NULL) {
> +    reply_with_error ("%s is btrfs root", subvolume);
> +    return NULL;
> +  }
> +
> +  /* The first line is the path of the subvolume. */
> +  if (key && !value) {
> +    if (add_string (&ret, "path") == -1)
> +      return NULL;
> +    if (add_string (&ret, key) == -1)
> +      return NULL;
> +  } else {
> +    if (add_string (&ret, key) == -1)
> +      return NULL;
> +    if (add_string (&ret, value) == -1)
> +      return NULL;
> +  }
> +
> +  /* Read the lines and split into "key: value". */
> +  p = analyze_line(p, &key, &value);
> +  while (key) {
> +    /* snapshot is special, see the output above */
> +    if (STREQLEN (key, "Snapshot(s)", sizeof
("Snapshot(s)") - 1)) {
> +      char *ss = NULL;
> +      int ss_len = 0;
> +
> +      if (add_string (&ret, key) == -1)
> +        return NULL;
> +
> +      p = analyze_line(p, &key, &value);
> +
> +      while (key && !value) {
> +          ss = realloc (ss, ss_len + strlen (key) + 1);
> +          if (!ss)
> +            return NULL;
> +
> +          if (ss_len != 0)
> +            ss[ss_len++] = ',';
> +
> +          memcpy (ss + ss_len, key, strlen (key));
> +          ss_len += strlen (key);
> +          ss[ss_len] = '\0';
> +
> +          p = analyze_line(p, &key, &value);
> +      }
> +
> +      if (ss) {
> +        if (add_string_nodup (&ret, ss) == -1) {
> +          free (ss);
> +          return NULL;
> +        }
> +      } else {
> +        if (add_string (&ret, "") == -1)
> +          return NULL;
> +      }
> +    } else {
> +      if (add_string (&ret, key ? key : "") == -1)
> +        return NULL;
> +      if (value && !STREQ(value, "-")) {
> +        if (add_string (&ret, value) == -1)
> +          return NULL;
> +      } else {
> +        if (add_string (&ret, "") == -1)
> +          return NULL;
> +      }
> +
> +      p = analyze_line(p, &key, &value);
> +    }
> +  }
> +
> +  if (end_stringsbuf (&ret) == -1)
> +    return NULL;
> +
> +  return ret.argv;
> +
> +}
> diff --git a/generator/actions.ml b/generator/actions.ml
> index 80c7ea7..d5ec528 100644
> --- a/generator/actions.ml
> +++ b/generator/actions.ml
> @@ -12036,6 +12036,15 @@ This uses the L<blockdev(8)> command."
};
>      longdesc = "\
>  Get the default subvolume or snapshot of a filesystem mounted at
C<mountpoint>." };
>
> +  { defaults with
> +    name = "btrfs_subvolume_show";
> +    style = RHashtable "btrfssubvolumeinfo", [Pathname
"subvolume"], [];
> +    proc_nr = Some 426;
> +    optional = Some "btrfs"; camel_name =
"BTRFSSubvolumeShow";
> +    shortdesc = "return detailed information of the subvolume";
> +    longdesc = "\
> +Return detailed information of the subvolume." };
> +
>  ]
>
>  (* Non-API meta-commands available only in guestfish.
> diff --git a/src/MAX_PROC_NR b/src/MAX_PROC_NR
> index 5e4a522..9f51d08 100644
> --- a/src/MAX_PROC_NR
> +++ b/src/MAX_PROC_NR
> @@ -1 +1 @@
> -425
> +426

This desperately needs tests.

Rich.

--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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