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

commit 8f5f02c460b7ca74ce55ce126ce0c1e58a3f923d upstream.

'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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index eae5266f27d172d1abbbe492676fa8da5bb69f6b..3512dd84347296c09124c071052876b527636ed6 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -409,6 +409,9 @@ 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);