[SCSI] enclosure: fix WARN_ON in dual path device removing

Bug report from: wenxiong@linux.vnet.ibm.com

The issue is happened in dual controller configuration. We got the
sysfs warnings when rmmod the ipr module.

enclosure_unregister() in drivers/msic/enclosure.c, call device_unregister()
for each componment deivce, device_unregister() ->device_del()->kobject_del()
->sysfs_remove_dir(). In sysfs_remove_dir(), set kobj->sd = NULL.

For each componment device,
enclosure_component_release()->enclosure_remove_links()->sysfs_remove_link()
in which checking kobj->sd again, it has been set as NULL when doing
device_unregister. So we saw all these sysfs WARNING.

Tested-by: wenxiong@linux.vnet.ibm.com
Cc: stable@vger.kernel.org
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

diff --git a/drivers/misc/enclosure.c b/drivers/misc/enclosure.c
index 0e8df41aaf144c7a00818bb95959a58060c99efe..2cf2bbc0b927e7d46f381d507dd0729d3bdab23c 100644 (file)
--- a/drivers/misc/enclosure.c
+++ b/drivers/misc/enclosure.c
@@ -198,6 +198,13 @@ static void enclosure_remove_links(struct enclosure_component *cdev)
 {
        char name[ENCLOSURE_NAME_SIZE];
 
+       /*
+        * In odd circumstances, like multipath devices, something else may
+        * already have removed the links, so check for this condition first.
+        */
+       if (!cdev->dev->kobj.sd)
+               return;
+
        enclosure_link_name(cdev, name);
        sysfs_remove_link(&cdev->dev->kobj, name);
        sysfs_remove_link(&cdev->cdev.kobj, "device");