[Vivid][SRU][patch]init: fix regression by supporting devices with major:minor:offset format

[Andy Whitcroft]

On Mon, May 11, 2015 at 07:11:24AM +0000, Zhang, Xiong Y wrote:
> The system will reboot after resuming from S4 on 15.04.
> The following commit fixes this broken.
> 
> commit cb31ef485dd4c6a205d1064b42027f82076d00c8
> Author: Chen Yu <yu.c.chen at intel.com>
> Date:   Sun May 3 22:35:05 2015 +0800
> 
>     init: fix regression by supporting devices with major:minor:offset format
> 
>     Commit 283e7ad02 ("init: stricter checking of major:minor root=
>     values") was so strict that it exposed the fact that a previously
>     unknown device format was being used.
> 
>     Distributions like Ubuntu uses klibc (rather than uswsusp) to resume
>     system from hibernation.  klibc expressed the swap partition/file in
>     the form of major:minor:offset.  For example, 8:3:0 represents a swap
>     partition in klibc, and klibc's resume process in initrd will finally
>     echo 8:3:0 to /sys/power/resume for manually resuming.  However, due
>     to commit 283e7ad02's stricter checking, 8:3:0 will be treated as an
>     invalid device format, and manual resuming from hibernation will fail.
> 
>     Fix this by adding support for devices with major:minor:offset format
>     when resuming from hibernation.
> 
>     Reported-by: Prigent, Christophe <christophe.prigent at intel.com>
>     Signed-off-by: Chen Yu <yu.c.chen at intel.com>
>     Acked-by: Rafael J. Wysocki <rjw at rjwysocki.net>
>     Signed-off-by: Mike Snitzer <snitzer at redhat.com>
> 
> diff --git a/init/do_mounts.c b/init/do_mounts.c
> index 8369ffa..a95bbdb 100644
> --- a/init/do_mounts.c
> +++ b/init/do_mounts.c
> @@ -225,10 +225,11 @@ dev_t name_to_dev_t(const char *name)
>  #endif
> 
>         if (strncmp(name, "/dev/", 5) != 0) {
> -               unsigned maj, min;
> +               unsigned maj, min, offset;
>                 char dummy;
> 
> -               if (sscanf(name, "%u:%u%c", &maj, &min, &dummy) == 2) {
> +               if ((sscanf(name, "%u:%u%c", &maj, &min, &dummy) == 2) ||
> +                   (sscanf(name, "%u:%u:%u:%c", &maj, &min, &offset, &dummy) == 3)) {
>                         res = MKDEV(maj, min);
>                         if (maj != MAJOR(res) || min != MINOR(res))
>                                 goto fail;

Does this _actually_ do what is claimed?  it actually appears to add
support for 8:3:0: as a format?

-apw