[PATCH] [152/275] md: correctly handle probe of an 'mdp' device.

[Andi Kleen]

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: NeilBrown <neilb@xxxxxxx>

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@xxxxxxxxxxx
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>

---
 drivers/md/md.c |    3 +++
 1 file changed, 3 insertions(+)

Index: linux-2.6.35.y/drivers/md/md.c
===================================================================
--- linux-2.6.35.y.orig/drivers/md/md.c	2011-03-29 23:02:59.630309629 -0700
+++ linux-2.6.35.y/drivers/md/md.c	2011-03-29 23:53:36.584601568 -0700
@@ -441,6 +441,9 @@
 {
 	mddev_t *mddev, *new = NULL;
 
+	if (unit && MAJOR(unit) != MD_MAJOR)
+		unit &= ~((1<<MdpMinorShift)-1);
+
  retry:
 	spin_lock(&all_mddevs_lock);
 
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