linux-kernel - [PATCH 3.12 33/62] SCSI: enclosure: fix WARN

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Date:	Tue, 10 Dec 2013 00:01:04 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, James Bottomley <JBottomley@...allels.com>
Subject: [PATCH 3.12 33/62] SCSI: enclosure: fix WARN_ON in dual path device removing

3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: James Bottomley <JBottomley@...allels.com>

commit a1470c7bf3a4676e62e4c0fb204e339399eb5c59 upstream.

Bug report from: wenxiong@...ux.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@...ux.vnet.ibm.com
Signed-off-by: James Bottomley <JBottomley@...allels.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/misc/enclosure.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/drivers/misc/enclosure.c
+++ b/drivers/misc/enclosure.c
@@ -198,6 +198,13 @@ static void enclosure_remove_links(struc
 {
 	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");


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