Re: [PATCH 2/2] grub2: use stat instead of udevadm for partition lookup

[Daniel Kiper]

On Thu, Jul 08, 2021 at 05:55:58PM +0200, Petr Vorel wrote:
> From: Jeff Mahoney <jeffm@suse.com>
>
> sysfs_partition_path calls udevadm to resolve the sysfs path for
> a block device. That can be accomplished by stating the device node
> and using the major/minor to follow the symlinks in /sys/dev/block/.
>
> This cuts the execution time of grub2-mkconfig from 10s to 2s on
> my system.
>
> Signed-off-by: Jeff Mahoney <jeffm@suse.com>
> [ pvorel: include grub/osdep/major.h ]
> Signed-off-by: Petr Vorel <pvorel@suse.cz>
> ---
>  grub-core/osdep/linux/hostdisk.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/grub-core/osdep/linux/hostdisk.c 
> b/grub-core/osdep/linux/hostdisk.c
> index da62f924e..43dc4b0ba 100644
> --- a/grub-core/osdep/linux/hostdisk.c
> +++ b/grub-core/osdep/linux/hostdisk.c
> @@ -31,6 +31,7 @@
>  #include <grub/misc.h>
>  #include <grub/i18n.h>
>  #include <grub/list.h>
> +#include <grub/osdep/major.h>
>
>  #include <stdio.h>
>  #include <stdlib.h>
> @@ -105,6 +106,13 @@ sysfs_partition_path (const char *dev, const char *entry)
>    char *buf = NULL;
>    size_t len = 0;
>    char *path = NULL;
> +  struct stat st;
> +  int ret;
> +
> +  ret = stat(dev, &st);

Missing space between "stat" and "(".

> +  if (ret == 0 && S_ISBLK(st.st_mode))

Same for S_ISBLK...

> +    return xasprintf ("/sys/dev/block/%u:%u/%s",
> +                   major (st.st_rdev), minor (st.st_rdev), entry);
>
>    argv[0] = "udevadm";
>    argv[1] = "info";

Do we really need udevadm fallback mechanism? If something went wrong
here for us I do not expect it will work for udevadm either.

Daniel