mtd: Raise limit on block device minor numbers

add_mtd_blktrans_dev() imposes a maximum of 257 devices per block
translator.  This was presumably meant to prevent overflow back in the
days of 8-bit minor numbers.  Instead, check against MINORMASK and the
limits of the partition naming scheme.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
index 85a52b3c7698..2f8c202dbd86 100644
--- a/drivers/mtd/mtd_blkdevs.c
+++ b/drivers/mtd/mtd_blkdevs.c
@@ -242,9 +242,12 @@ int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
         if (new->devnum == -1)
                 new->devnum = last_devnum+1;
 
-        if ((new->devnum << tr->part_bits) > 256) {
+        /* Check that the device and any partitions will get valid
+         * minor numbers and that the disk naming code below can cope
+         * with this number. */
+        if (new->devnum > (MINORMASK >> tr->part_bits) ||
+            (tr->part_bits && new->devnum >= 27 * 26))
                 return -EBUSY;
-        }
 
         list_add_tail(&new->list, &tr->devs);
  added: