Re: [PATCH v4 07/53] tools api fs: Avoid reading whole file for a 1 byte bool

[Namhyung Kim <namhyung@kernel.org>]

On Thu, Nov 2, 2023 at 10:58 AM Ian Rogers <irogers@google.com> wrote:
>
> sysfs__read_bool used the first byte from a fully read file into a
> string. It then looked at the first byte's value. Avoid doing this and
> just read the first byte.
>
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/lib/api/fs/fs.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
> index 496812b5f1d2..4c35a689d1fc 100644
> --- a/tools/lib/api/fs/fs.c
> +++ b/tools/lib/api/fs/fs.c
> @@ -447,15 +447,16 @@ int sysfs__read_str(const char *entry, char **buf, size_t *sizep)
>
>  int sysfs__read_bool(const char *entry, bool *value)
>  {
> -       char *buf;
> -       size_t size;
> -       int ret;
> +       struct io io;
> +       char bf[16];
> +       int ret = 0;
>
> -       ret = sysfs__read_str(entry, &buf, &size);
> -       if (ret < 0)
> -               return ret;
> +       io.fd = open(entry, O_RDONLY);

The entry is a name in sysfs, so you need to get the full name.

Thanks,
Namhyung


> +       if (io.fd < 0)
> +               return -errno;
>
> -       switch (buf[0]) {
> +       io__init(&io, io.fd, bf, sizeof(bf));
> +       switch (io__get_char(&io)) {
>         case '1':
>         case 'y':
>         case 'Y':
> @@ -469,8 +470,7 @@ int sysfs__read_bool(const char *entry, bool *value)
>         default:
>                 ret = -1;
>         }
> -
> -       free(buf);
> +       close(io.fd);
>
>         return ret;
>  }
> --
> 2.42.0.869.gea05f2083d-goog
>