[LTP] [PATCH v2] tst_dev_bytes_written: parsing /proc/diskstats instead of sys file

[Sumit Garg]

On Mon, 6 Jan 2020 at 14:00, Yang Xu <xuyang2018.jy@cn.fujitsu.com> wrote:
>
> Now, tst_dev_bytes_written api can get the whole disk stat correctly(such as /dev/sda),
> but can not get partition stat correctly(such as /dev/sda5).
> fail as below:
> export LTP_DEV=/dev/sda5
> tst_device.c:388: CONF: Test device stat file: /sys/block/sda5/stat not found
>
> To fix this, use /proc/diskstats to parse instead of /sys/block/<devices>/stat.
> Data format as same as diskstats_show function in kernel genhd.c[1].
>
> Also, add hint when loop driver doesn't support blk-mq[2]. So that, user can export
> LTP_DEV to test.
>
> [1]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/block/genhd.c
> [2]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b5dd2f60
>
> Signed-off-by: Yang Xu <xuyang2018.jy@cn.fujitsu.com>
> ---
>  lib/tst_device.c | 26 ++++++++++++--------------
>  1 file changed, 12 insertions(+), 14 deletions(-)
>

Reviewed-by: Sumit Garg <sumit.garg@linaro.org>

> diff --git a/lib/tst_device.c b/lib/tst_device.c
> index 10f71901d..ad764a38d 100644
> --- a/lib/tst_device.c
> +++ b/lib/tst_device.c
> @@ -375,24 +375,22 @@ int tst_umount(const char *path)
>
>  unsigned long tst_dev_bytes_written(const char *dev)
>  {
> -       struct stat st;
> -       unsigned long dev_sec_write = 0, dev_bytes_written, io_ticks = 0;
> -       char dev_stat_path[1024];
> -
> -       snprintf(dev_stat_path, sizeof(dev_stat_path), "/sys/block/%s/stat",
> -                strrchr(dev, '/') + 1);
> +       unsigned long dev_sec_write = 0, dev_bytes_written;
> +       unsigned int io_ticks = 0;
> +       char fmt[1024];
>
> -       if (stat(dev_stat_path, &st) != 0)
> -               tst_brkm(TCONF, NULL, "Test device stat file: %s not found",
> -                        dev_stat_path);
> +       sprintf(fmt, "%%*4d %%*7d %s %%*lu %%*lu %%*lu %%*u %%*lu %%*lu %%lu %%*u %%*u %%u",
> +                       strrchr(dev, '/') + 1);
>
> -       SAFE_FILE_SCANF(NULL, dev_stat_path,
> -                       "%*s %*s %*s %*s %*s %*s %lu %*s %*s %lu",
> -                       &dev_sec_write, &io_ticks);
> +       SAFE_FILE_LINES_SCANF(NULL, "/proc/diskstats", fmt, &dev_sec_write, &io_ticks);
>
> +       /* If we create block device by attaching a free loop device, loop driver
> +        * needs to support blk-mq(commit b5dd2f6047c), so that kernel can get I/O
> +        * statistics about loop device.
> +        */
>         if (!io_ticks)
> -               tst_brkm(TCONF, NULL, "Test device stat file: %s broken",
> -                        dev_stat_path);
> +               tst_brkm(TCONF, NULL, "io_ticks on test device %s is always 0, "
> +                               "export LTP_DEV to test", dev);
>
>         dev_bytes_written = (dev_sec_write - prev_dev_sec_write) * 512;
>
> --
> 2.18.0
>
>
>