[PATCH] Get mdraid 1.x array size from data_size if size is zero

[Colin Watson]

On RAID-0 devices, the 'size' member in the RAID superblock is 0,
meaning (as far as I can tell) "use all available space in physical
volume".  GRUB's mdraid 0.9 support handles this, but its mdraid 1.x
support does not.  The 'data_size' member is more useful.

I've continued using 'size' if it's non-zero, partly for minimal risk to
1.99 (so this shouldn't break anything that currently works) and partly
because 'data_size' is a bit larger than 'size' on RAID-1 and I thought
we probably ought to use the smaller size in case the larger size
included some kind of reserved blocks.  I didn't have time to unpick the
full details of the differences from mdadm.

This was originally reported as:

  https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/743136

2011-03-28  Colin Watson  <address@hidden>

        * grub-core/disk/mdraid1x_linux.c (grub_mdraid_detect): If
        real_sb->size is zero (e.g. RAID-0), get the disk size from
        real_sb->data_size instead.
        Fixes Ubuntu bug #743136.

=== modified file 'grub-core/disk/mdraid1x_linux.c'
--- grub-core/disk/mdraid1x_linux.c     2011-03-28 14:17:22 +0000
+++ grub-core/disk/mdraid1x_linux.c     2011-03-28 15:18:10 +0000
@@ -192,7 +192,10 @@ grub_mdraid_detect (grub_disk_t disk, st
        array->level = grub_le_to_cpu32 (real_sb->level);
        array->layout = grub_le_to_cpu32 (real_sb->layout);
        array->total_devs = grub_le_to_cpu32 (real_sb->raid_disks);
-       array->disk_size = grub_le_to_cpu64 (real_sb->size);
+       if (real_sb->size)
+         array->disk_size = grub_le_to_cpu64 (real_sb->size);
+       else
+         array->disk_size = grub_le_to_cpu64 (real_sb->data_size);
        array->chunk_size = grub_le_to_cpu32 (real_sb->chunksize);
 
        if (grub_le_to_cpu32 (real_sb->dev_number) >=

-- 
Colin Watson                                       address@hidden