md: avoid endless recovery loop when waiting for fail device to compl…

…ete.

If a device fails in a way that causes pending request to take a while
to complete, md will not be able to immediately remove it from the
array in remove_and_add_spares.
It will then incorrectly look like a spare device and md will try to
recover it even though it is failed.
This leads to a recovery process starting and instantly aborting over
and over again.

We should check if the device is faulty before considering it to be a
spare.  This will avoid trying to start a recovery that cannot
proceed.

This bug was introduced in 2.6.26 so that patch is suitable for any
kernel since then.

Cc: [email protected]
Reported-by: Jim Paradis <[email protected]>
Signed-off-by: NeilBrown <[email protected]>

drivers/md/md.c

@@ -7088,6 +7088,7 @@ static int remove_and_add_spares(mddev_t *mddev)
 		list_for_each_entry(rdev, &mddev->disks, same_set) {
 			if (rdev->raid_disk >= 0 &&
 			    !test_bit(In_sync, &rdev->flags) &&
+			    !test_bit(Faulty, &rdev->flags) &&
 			    !test_bit(Blocked, &rdev->flags))
 				spares++;
 			if (rdev->raid_disk < 0