[PATCH 3.5 38/62] fs/proc/proc_devtree.c: remove empty /proc/device-tree when no openfirmware exists.

[Luis Henriques]

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

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

From: Dave Jones <davej at redhat.com>

commit c1d867a54d426b45da017fbe8e585f8a3064ce8d upstream.

Distribution kernels might want to build in support for /proc/device-tree
for kernels that might end up running on hardware that doesn't support
openfirmware.  This results in an empty /proc/device-tree existing.
Remove it if the OFW root node doesn't exist.

This situation actually confuses grub2, resulting in install failures.
grub2 sees the /proc/device-tree and picks the wrong install target cf.
http://bzr.savannah.gnu.org/lh/grub/trunk/grub/annotate/4300/util/grub-install.in#L311
grub should be more robust, but still, leaving an empty proc dir seems
pointless.

Addresses https://bugzilla.redhat.com/show_bug.cgi?id=818378.

Signed-off-by: Dave Jones <davej at redhat.com>
Cc: Al Viro <viro at ZenIV.linux.org.uk>
Cc: Paul Mackerras <paulus at samba.org>
Cc: Josh Boyer <jwboyer at fedoraproject.org>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/proc/proc_devtree.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/proc/proc_devtree.c b/fs/proc/proc_devtree.c
index 927cbd1..f060f28 100644
--- a/fs/proc/proc_devtree.c
+++ b/fs/proc/proc_devtree.c
@@ -233,6 +233,7 @@ void __init proc_device_tree_init(void)
 		return;
 	root = of_find_node_by_path("/");
 	if (root == NULL) {
+		remove_proc_entry("device-tree", NULL);
 		pr_debug("/proc/device-tree: can't find root\n");
 		return;
 	}
-- 
1.9.0