mtd: cmdlinepart: make the partitions rule more strict

Huang Shijie <shijie8@gmail.com> explains:

Assume we have a 1GiB(8Gib) NAND chip, and we set the partitions
in the command line like this:
    #gpmi-nand:100m(boot),100m(kernel),1g(rootfs)

In this case, the partition truncating occurs. The current code will
get the following result:

     ----------------------------------
        root@freescale ~$ cat /proc/mtd
        dev:    size   erasesize  name
        mtd0: 06400000 00040000 "boot"
        mtd1: 06400000 00040000 "kernel"
     ----------------------------------

It is obvious that we lost the truncated partition `rootfs` which should
be 824MiB in this case.

Also, forbid 0-sized partitions.

Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/cmdlinepart.c

@@ -319,12 +319,22 @@ static int parse_cmdline_partitions(struct mtd_info *master,
 				if (part->parts[i].size == SIZE_REMAINING)
 					part->parts[i].size = master->size - offset;
 
+				if (part->parts[i].size == 0) {
+					printk(KERN_WARNING ERRP
+					       "%s: skipping zero sized partition\n",
+					       part->mtd_id);
+					part->num_parts--;
+					memmove(&part->parts[i],
+						&part->parts[i + 1],
+						sizeof(*part->parts) * (part->num_parts - i));
+					continue;
+				}
+
 				if (offset + part->parts[i].size > master->size) {
 					printk(KERN_WARNING ERRP
 					       "%s: partitioning exceeds flash size, truncating\n",
 					       part->mtd_id);
 					part->parts[i].size = master->size - offset;
-					part->num_parts = i;
 				}
 				offset += part->parts[i].size;
 			}