[dm-devel] [PATCH] uevent_can_discard: optimize devpath check

[Christophe Varoqui]

Applied.
Thanks.

On Wed, Mar 1, 2017 at 6:22 PM, Martin Wilck <mwilck at suse.com> wrote:

> This uses roughly 10% cycles of the sscanf-based implementation.
>
> Improves: ee8888f0 "multipath-tools: improve processing efficiency..."
> Signed-off-by: Martin Wilck <mwilck at suse.com>
> ---
>  libmultipath/uevent.c | 37 +++++++++++++++++++++++--------------
>  1 file changed, 23 insertions(+), 14 deletions(-)
>
> diff --git a/libmultipath/uevent.c b/libmultipath/uevent.c
> index 6e2527bd..367e129a 100644
> --- a/libmultipath/uevent.c
> +++ b/libmultipath/uevent.c
> @@ -143,26 +143,35 @@ uevent_need_merge(void)
>         return need_merge;
>  }
>
> +static bool
> +uevent_can_discard_by_devpath(const char *devpath)
> +{
> +       static const char BLOCK[] = "/block/";
> +       const char *tmp = strstr(devpath, BLOCK);
> +
> +       if (tmp == NULL) {
> +               condlog(4, "no /block/ in '%s'", devpath);
> +               return true;
> +       }
> +       tmp += sizeof(BLOCK) - 1;
> +       if (*tmp == '\0')
> +               /* just ".../block/" - discard */
> +               return true;
> +       /*
> +        * If there are more path elements after ".../block/xyz",
> +        * it's a partition - discard it; but don't discard
> ".../block/sda/".
> +        */
> +       tmp = strchr(tmp, '/');
> +       return tmp != NULL && *(tmp + 1) != '\0';
> +}
> +
>  bool
>  uevent_can_discard(struct uevent *uev)
>  {
> -       char *tmp;
> -       char a[11], b[11];
>         struct config * conf;
>
> -       /*
> -        * keep only block devices, discard partitions
> -        */
> -       tmp = strstr(uev->devpath, "/block/");
> -       if (tmp == NULL){
> -               condlog(4, "no /block/ in '%s'", uev->devpath);
> +       if (uevent_can_discard_by_devpath(uev->devpath))
>                 return true;
> -       }
> -       if (sscanf(tmp, "/block/%10s", a) != 1 ||
> -           sscanf(tmp, "/block/%10[^/]/%10s", a, b) == 2) {
> -               condlog(4, "discard event on %s", uev->devpath);
> -               return true;
> -       }
>
>         /*
>          * do not filter dm devices by devnode
> --
> 2.12.0
>
> --
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