[PATCH RFC] enclosure: fix sysfs symlinks creation when using multipath

[Maurizio Lombardi <mlombard@redhat.com>]

With multipath, it may happen that the same device is passed
to enclosure_add_device() multiple times and that the enclosure_add_links()
function fails to create the symlinks because the device's sysfs
directory entry is still NULL.
In this case, the links will never be created because all the subsequent
calls to enclosure_add_device() will immediately fail with EEXIST.

This patch modifies the code so the driver will detect this condition
and will retry to create the symlinks when enclosure_add_device() is called.

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
---
 drivers/misc/enclosure.c  | 16 ++++++++++++++--
 include/linux/enclosure.h |  1 +
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/enclosure.c b/drivers/misc/enclosure.c
index 65fed71..a856c98 100644
--- a/drivers/misc/enclosure.c
+++ b/drivers/misc/enclosure.c
@@ -375,21 +375,33 @@ int enclosure_add_device(struct enclosure_device *edev, int component,
 			 struct device *dev)
 {
 	struct enclosure_component *cdev;
+	int error;
 
 	if (!edev || component >= edev->components)
 		return -EINVAL;
 
 	cdev = &edev->component[component];
 
-	if (cdev->dev == dev)
+	if (cdev->dev == dev) {
+		if (!cdev->links_created) {
+			error = enclosure_add_links(cdev);
+			if (!error)
+				cdev->links_created = 1;
+		}
 		return -EEXIST;
+	}
 
 	if (cdev->dev)
 		enclosure_remove_links(cdev);
 
 	put_device(cdev->dev);
 	cdev->dev = get_device(dev);
-	return enclosure_add_links(cdev);
+	error = enclosure_add_links(cdev);
+	if (!error)
+		cdev->links_created = 1;
+	else
+		cdev->links_created = 0;
+	return error;
 }
 EXPORT_SYMBOL_GPL(enclosure_add_device);
 
diff --git a/include/linux/enclosure.h b/include/linux/enclosure.h
index a4cf57c..c3bdc4c 100644
--- a/include/linux/enclosure.h
+++ b/include/linux/enclosure.h
@@ -97,6 +97,7 @@ struct enclosure_component {
 	struct device cdev;
 	struct device *dev;
 	enum enclosure_component_type type;
+	int links_created;
 	int number;
 	int fault;
 	int active;
-- 
Maurizio Lombardi