Preserve starting sector for primary NTFS 3.1 partitions (Windows Vista)

when modifying the DOS disk label.  NTFS 3.1 partitions do not start on
the 2nd head of the 1st cylinder at the beginning of the drive.

diff --git a/libparted/labels/dos.c b/libparted/labels/dos.c
index fda8a79..0a606e5 100644 (file)
--- a/libparted/labels/dos.c
+++ b/libparted/labels/dos.c
@@ -1544,11 +1544,16 @@ _primary_constraint (const PedDisk* disk, const PedCHSGeometry* bios_geom,
 
 /* This constraint is for partitions starting on the first cylinder.  They
  * must start on the 2nd head of the 1st cylinder.
+ *
+ * NOTE: We don't always start on the 2nd head of the 1st cylinder.  Windows
+ * Vista aligns starting partitions at sector 2048 (0x800) by default.  See:
+ * http://support.microsoft.com/kb/923332
  */
 static PedConstraint*
 _primary_start_constraint (const PedDisk* disk,
+                           const PedPartition *part,
                            const PedCHSGeometry* bios_geom,
-                          const PedGeometry* min_geom)
+                           const PedGeometry* min_geom)
 {
        PedDevice*      dev = disk->dev;
        PedSector       cylinder_size = bios_geom->sectors * bios_geom->heads;
@@ -1556,21 +1561,30 @@ _primary_start_constraint (const PedDisk* disk,
        PedAlignment    end_align;
        PedGeometry     start_geom;
        PedGeometry     end_geom;
+       PedGeometry start_pos;
+
+       if (part->geom.start == 2048)
+               /* check for known Windows Vista (NTFS >= 3.1) alignments */
+               /* sector 0x800 == 2048                                   */
+               start_pos = 2048;
+       else
+               /* all other primary partitions on a DOS label align to   */
+               /* the 2nd head of the first cylinder (0x3F == 63)        */
+               start_pos = bios_geom->sectors;
 
-       if (!ped_alignment_init (&start_align, bios_geom->sectors, 0))
+       if (!ped_alignment_init (&start_align, start_pos, 0))
                return NULL;
        if (!ped_alignment_init (&end_align, -1, cylinder_size))
                return NULL;
        if (min_geom) {
-               if (!ped_geometry_init (&start_geom, dev,
-                                       bios_geom->sectors, 1))
+               if (!ped_geometry_init (&start_geom, dev, start_pos, 1))
                        return NULL;
                if (!ped_geometry_init (&end_geom, dev, min_geom->end,
                                        dev->length - min_geom->end))
                        return NULL;
        } else {
-               if (!ped_geometry_init (&start_geom, dev, bios_geom->sectors,
-                                       dev->length - bios_geom->sectors))
+               if (!ped_geometry_init (&start_geom, dev, start_pos,
+                       dev->length - start_pos))
                        return NULL;
                if (!ped_geometry_init (&end_geom, dev, 0, dev->length))
                        return NULL;
@@ -1678,12 +1692,14 @@ _align_primary (PedPartition* part, const PedCHSGeometry* bios_geom,
 
        solution = _best_solution (part, bios_geom, solution,
                        _try_constraint (part, constraint,
-                                        _primary_start_constraint (disk,
+                                        _primary_start_constraint (disk, part,
                                                 bios_geom, min_geom)));
-       solution = _best_solution (part, bios_geom, solution,
+
+       if (!solution)
+               solution = _best_solution (part, bios_geom, solution,
                        _try_constraint (part, constraint,
-                                        _primary_constraint (disk, bios_geom,
-                                                min_geom)));
+                               _primary_constraint (disk, bios_geom,
+                               min_geom)));
 
        if (min_geom)
                ped_geometry_destroy (min_geom);