[Libguestfs] [PATCH] New API: btrfs_device_stats

[Pino Toscano]

On Tuesday 16 June 2015 17:10:09 Cao jin wrote:
> Also modified a public function: analyze_line, make it more flexible

The addition of the parameter to analyze_line should be in an own
patch. Can you please decouple it?

> Signed-off-by: Cao jin <caoj.fnst at cn.fujitsu.com>
> ---
>  daemon/btrfs.c       | 83 +++++++++++++++++++++++++++++++++++++++++++++++-----
>  generator/actions.ml | 12 ++++++++
>  2 files changed, 88 insertions(+), 7 deletions(-)
> 
> diff --git a/daemon/btrfs.c b/daemon/btrfs.c
> index 39392f7..f913f66 100644
> --- a/daemon/btrfs.c
> +++ b/daemon/btrfs.c
> @@ -853,11 +853,11 @@ do_btrfs_fsck (const char *device, int64_t superblock, int repair)
>   * returns the next position following \n.
>   */
>  static char *
> -analyze_line (char *line, char **key, char **value)
> +analyze_line (char *line, char **key, char **value, char delim)
>  {
>    char *p = line;
>    char *next = NULL;
> -  char delimiter = ':';
> +  char delimiter = delim;
>    char *del_pos = NULL;
>  
>    if (!line || *line == '\0') {

Why keep the local variable 'delimiter'? Just name the argument like
that.

> @@ -964,7 +964,7 @@ do_btrfs_subvolume_show (const char *subvolume)
>     *                                 snapshots/test3
>     *
>     */
> -  p = analyze_line(out, &key, &value);
> +  p = analyze_line(out, &key, &value, ':');
>    if (!p) {
>      reply_with_error ("truncated output: %s", out);
>      return NULL;
> @@ -984,7 +984,7 @@ do_btrfs_subvolume_show (const char *subvolume)
>    }
>  
>    /* Read the lines and split into "key: value". */
> -  p = analyze_line(p, &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)) {
> @@ -994,7 +994,7 @@ do_btrfs_subvolume_show (const char *subvolume)
>        if (add_string (&ret, key) == -1)
>          return NULL;
>  
> -      p = analyze_line(p, &key, &value);
> +      p = analyze_line(p, &key, &value, ':');
>  
>        while (key && !value) {
>            ss = realloc (ss, ss_len + strlen (key) + 1);
> @@ -1008,7 +1008,7 @@ do_btrfs_subvolume_show (const char *subvolume)
>            ss_len += strlen (key);
>            ss[ss_len] = '\0';
>  
> -          p = analyze_line(p, &key, &value);
> +          p = analyze_line(p, &key, &value, ':');
>        }
>  
>        if (ss) {
> @@ -1031,7 +1031,7 @@ do_btrfs_subvolume_show (const char *subvolume)
>            return NULL;
>        }
>  
> -      p = analyze_line(p, &key, &value);
> +      p = analyze_line(p, &key, &value, ':');
>      }
>    }
>  
> @@ -2083,3 +2083,72 @@ do_btrfs_image (char *const *sources, const char *image,
>  
>    return 0;
>  }
> +
> +char **
> +do_btrfs_device_stats (const char *path, int zero)
> +{
> +  const size_t MAX_ARGS = 64;
> +  const char *argv[MAX_ARGS];
> +  size_t i = 0;
> +  CLEANUP_FREE char *buf = NULL;
> +  CLEANUP_FREE char *err = NULL;
> +  CLEANUP_FREE char *out = NULL;
> +  char *p, *key = NULL, *value = NULL;
> +  DECLARE_STRINGSBUF (ret);

'ret' is leaked if returning before "return ret.argv".

> +  int r;
> +  int is_dev;
> +
> +  is_dev = STREQLEN (path, "/dev/", 5);
> +  buf = is_dev ? strdup (path) : sysroot_path (path);
> +  if (buf == NULL) {
> +    reply_with_perror ("malloc");
> +    return NULL;
> +  }
> +
> +
> +  ADD_ARG (argv, i, str_btrfs);
> +  ADD_ARG (argv, i, "device");
> +  ADD_ARG (argv, i, "stats");
> +  ADD_ARG (argv, i, buf);
> +
> +  if ((optargs_bitmask & GUESTFS_BTRFS_DEVICE_STATS_ZERO_BITMASK) && zero) {
> +    ADD_ARG (argv, i, "-z");
> +  }
> +
> +  ADD_ARG (argv, i, NULL);
> +
> +  r = commandv (&out, &err, argv);
> +  if (r == -1) {
> +    reply_with_error ("%s: %s", path, err);
> +    return NULL;
> +  }
> +
> +  /* Output pattern is:
> +   *
> +   *  [/dev/sda].write_io_errs   0
> +   *  [/dev/sda].read_io_errs    0
> +   *  [/dev/sda].flush_io_errs   0
> +   *  [/dev/sda].corruption_errs 0
> +   *  [/dev/sda].generation_errs 0
> +   *
> +  */
> +
> +  /* Read the lines and split into "key: value". */
> +  p = analyze_line(out, &key, &value, ' ');
> +  while(key)
> +  {

Curly bracket goes to the line before, and please remember the space
between function and opening round bracket...

> +    if (add_string (&ret, key) == -1)
> +      return NULL;
> +
> +    if (add_string (&ret, value) == -1)
> +      return NULL;
> +
> +    p = analyze_line(p, &key, &value, ' ');
> +  }

This means that the return "hash" will have keys like:
  [/dev/sda].write_io_errs
? Wouldn't it better to just return the name of the attribute, i.e.
  write_io_errs
?

> diff --git a/generator/actions.ml b/generator/actions.ml
> index d5e5ccf..dfb42b5 100644
> --- a/generator/actions.ml
> +++ b/generator/actions.ml
> @@ -12593,6 +12593,18 @@ numbered C<partnum> on device C<device>.
>  
>  It returns C<primary>, C<logical>, or C<extended>." };
>  
> +  { defaults with
> +    name = "btrfs_device_stats"; added = (1, 29, 46);
> +    style = RHashtable "devicestats", [Dev_or_Path "path"], [OBool "zero"];
> +    proc_nr = Some 456;
> +    optional = Some "btrfs"; camel_name = "BTRFSDeviceStats";
> +    shortdesc = "read and print the device IO stats for mounted btrfs device";
> +    longdesc = "\
> +Read and print the device IO stats for all mounted devices of the filesystem
> +identified by C<path>, or for a single device identified by C<path>.
> +
> +If you want to reset stats to zero after reading them, use option: zero:true." };

The 'zero' parameter adds side-effects to a "query" API, and this does
not seem too good.

If you want a way to reset this kind of btrfs metadata, then please
add a separate / well distinct API for it. Just because btrfs
subcommands have that awkward parameters, it doesn't mean we need to
map them 1:1 in libguestfs.

Thanks,
-- 
Pino Toscano