[Bug 1527727] Re: grub-probe for zfs assumes all devices prefix with /dev, ignoring /dev/disk/...

[Chad Miller]

Attached is debdiff. Important change is in grub-
core/osdep/unix/getroot.c, function
grub_util_find_root_devices_from_poolname


+--- a/grub-core/osdep/unix/getroot.c
++++ b/grub-core/osdep/unix/getroot.c
+@@ -305,8 +305,18 @@ grub_util_find_root_devices_from_poolnam
+         }
+       if (name[0] == '/')
+         devices[ndevices++] = xstrdup (name);
+-      else
+-        devices[ndevices++] = xasprintf ("/dev/%s", name);
++      else {
++        const char *middles[] = { "disk/by-id/", "disk/by-uuid/", "disk/by-partuuid/", "disk/by-label/", "disk/by-partlabel/", "disk/by-path/", "/", NULL };
++
++        for (const char **cursor = middles; *cursor != NULL; cursor++) {
++          char *proposed = xasprintf ("/dev/%s/%s", *cursor, name);
++          struct stat stt;
++          if (lstat (proposed, &stt) == 0) {
++            devices[ndevices++] = proposed;
++            break;    
++          }
++        }
++      }
+         }
+       break;
+     }


** Attachment added: "xenial debdiff"
   https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1527727/+attachment/4537081/+files/diff

** Changed in: grub2 (Ubuntu)
       Status: New => Confirmed

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https://bugs.launchpad.net/bugs/1527727

Title:
  grub-probe for zfs assumes all devices prefix with /dev, ignoring
  /dev/disk/...

Status in grub2 package in Ubuntu:
  Confirmed

Bug description:
  update-grub runs /usr/sbin/grub-probe

  /usr/sbin/grub-probe runs ["zpool", "status", poolname]

  zpool responds with device names as used at (I think!) pool creation
  time. Often, this is /dev/disk/by-id/... names, without the path.

  grub-probe then parses the output, and takes the names of devices, and
  if they do not start with a "/", it prepends "/dev/".

  It then tests the existence of the path name of the device. it fails.

  grub-probe then returns  something like

  /usr/sbin/grub-probe: error: failed to get canonical path of `/dev
  /ata-ST31000333AS_99999999-part1'.

  The actual path is of course /dev/disk/by-
  id/ST31000333AS_99999999-part1

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