From: Hannes Reinecke <hare@suse.de>
Date: Fri, 10 May 2013 09:06:16 +0000 (+0200)
Subject: [SCSI] sd: avoid deadlocks when running under multipath
X-Git-Tag: v3.11-rc1~88^2~85
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0761df9c4b2d966da3af2ac4ee7372afa681ce63;p=pandora-kernel.git

[SCSI] sd: avoid deadlocks when running under multipath

When multipathed systems run into an all-paths-down scenario
all devices might be dropped, too. This causes 'del_gendisk'
to be called, which will unregister the kobj_map->probe()
function for all disk device numbers.
When the device comes back the default ->probe() function
is run which will call __request_module(), which will
deadlock.
As 'del_gendisk' typically does _not_ trigger a module unload
the default ->probe() function is pointless anyway.
This patch implements a dummy ->probe() function, which will
just return NULL if the disk is not registered.
This will avoid the deadlock. Plus it'll speed up device
scanning.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
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