md: correctly handle probe of an 'mdp' device.

'mdp' devices are md devices with preallocated device numbers
for partitions. As such it is possible to mknod and open a partition
before opening the whole device.

this causes  md_probe() to be called with a device number of a
partition, which in-turn calls mddev_find with such a number.

However mddev_find expects the number of a 'whole device' and
does the wrong thing with partition numbers.

So add code to mddev_find to remove the 'partition' part of
a device number and just work with the 'whole device'.

This patch addresses https://bugzilla.kernel.org/show_bug.cgi?id=28652

Reported-by: hkmaly@bigfoot.com
Signed-off-by: NeilBrown <neilb@suse.de>
Cc: <stable@kernel.org>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 6818ff4aa8d61129324abe5e554942d9714404f8..330addfe9b77efccd779bd9f0261b1f6897fe389 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -553,6 +553,9 @@ static mddev_t * mddev_find(dev_t unit)
 {
        mddev_t *mddev, *new = NULL;
 
+       if (unit && MAJOR(unit) != MD_MAJOR)
+               unit &= ~((1<<MdpMinorShift)-1);
+
  retry:
        spin_lock(&all_mddevs_lock);