Re: [PATCH v3 2/6] ieee1275/powerpc: enables device mapper discovery

[avnish <avnish@imap.linux.ibm.com>]

On 2024-06-06 21:04, Vladimir 'phcoder' Serbinenko wrote:
> 2 problems: * How does dm device ends up on ofpathname? It should be
> handled by grub internal logic in most cases and not end up in
> of-specific paths * Why not use existing devmapper functions already
> present in codebase? Le jeu. 6 juin 2024,
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> 2 problems:
> * How does dm device ends up on ofpathname? It should be handled by
> grub internal logic in most cases and not end up in of-specific paths
> * Why not use existing devmapper functions already present in
> codebase?
> 

Hi Vladimir,
Thank you so much for your response!

We have observed that whenever we are dealing with the devices like 
"/dev/dm-*", the ofpath returns null.
To resolve this, as no such required functions has been implemented to 
handle this kind of case. We have done changes based on the requirement
that will look into /sys/block/dm-* devices and search slave
devices recursively inside slaves directory to find the root disk.

Regards,
Avnish Chouhan

> Le jeu. 6 juin 2024, 14:40, Avnish Chouhan <avnish@linux.ibm.com> a
> écrit :
> 
>> This patch enables the device mapper discovery on ofpath.c.
>> Currently,
>> when we are dealing with a device like /dev/dm-* the ofpath returns
>> null
>> since there is no function implemented to handle this case.
>> 
>> This patch implements a function that will look into /sys/block/dm-*
>> devices and search recursively inside slaves directory to find the
>> root
>> disk.
>> 
>> Signed-off-by: Diego Domingos <diegodo@br.ibm.com>
>> Signed-off-by: Avnish Chouhan <avnish@linux.ibm.com>
>> ---
>> grub-core/osdep/linux/ofpath.c | 64
>> +++++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 63 insertions(+), 1 deletion(-)
>> 
>> diff --git a/grub-core/osdep/linux/ofpath.c
>> b/grub-core/osdep/linux/ofpath.c
>> index 0f5d54e9f2d..cc849d9c94c 100644
>> --- a/grub-core/osdep/linux/ofpath.c
>> +++ b/grub-core/osdep/linux/ofpath.c
>> @@ -37,6 +37,7 @@
>> #include <fcntl.h>
>> #include <errno.h>
>> #include <ctype.h>
>> +#include <dirent.h>
>> 
>> #ifdef __sparc__
>> typedef enum
>> @@ -755,13 +756,74 @@ strip_trailing_digits (const char *p)
>> return new;
>> }
>> 
>> +static char *
>> +get_slave_from_dm (const char * device)
>> +{
>> +  char *curr_device, *tmp;
>> +  char *directory;
>> +  char *ret = NULL;
>> +  directory = grub_strdup (device);
>> +  tmp = get_basename (directory);
>> +  curr_device = grub_strdup (tmp);
>> +  *tmp = '\0';
>> +
>> +  /* Recursively check for slaves devices so we can find the root
>> device */
>> +  while ((curr_device[0] == 'd') && (curr_device[1] == 'm') &&
>> (curr_device[2] == '-'))
>> +    {
>> +      DIR *dp;
>> +      struct dirent *ep;
>> +      char* device_path;
>> +      device_path = grub_xasprintf ("/sys/block/%s/slaves",
>> curr_device);
>> +      dp = opendir (device_path);
>> +
>> +      if (dp != NULL)
>> +        {
>> +          ep = readdir (dp);
>> +
>> +          while (ep != NULL)
>> +            {
>> +              /* avoid some system directories */
>> +              if (!strcmp(ep->d_name,"."))
>> +                goto next_dir;
>> +              if (!strcmp(ep->d_name,".."))
>> +                goto next_dir;
>> +
>> +              free (curr_device);
>> +              free (ret);
>> +              curr_device = grub_strdup (ep->d_name);
>> +              ret = grub_xasprintf ("%s%s", directory,
>> curr_device);
>> +              break;
>> +
>> +              next_dir:
>> +              ep = readdir (dp);
>> +              continue;
>> +            }
>> +          closedir (dp);
>> +        }
>> +      else
>> +        grub_util_warn (_("cannot open directory `%s'"),
>> device_path);
>> +      free (device_path);
>> +    }
>> +  free (directory);
>> +  free (curr_device);
>> +
>> +  return ret;
>> +}
>> +
>> char *
>> grub_util_devname_to_ofpath (const char *sys_devname)
>> {
>> -  char *name_buf, *device, *devnode, *devicenode, *ofpath;
>> +  char *name_buf, *device, *devnode, *devicenode, *ofpath,
>> *realname;
>> 
>> name_buf = xrealpath (sys_devname);
>> 
>> +  realname = get_slave_from_dm (name_buf);
>> +  if (realname)
>> +    {
>> +      free (name_buf);
>> +      name_buf = realname;
>> +    }
>> +
>> device = get_basename (name_buf);
>> devnode = strip_trailing_digits (name_buf);
>> devicenode = strip_trailing_digits (device);
>> 
>> _______________________________________________
>> Grub-devel mailing list
>> Grub-devel@gnu.org
>> https://lists.gnu.org/mailman/listinfo/grub-devel
> 
> 
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