From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

It's not good to crash the machine if panic_on_warn() is set just
because someone made a stupid mistake of trying to create a sysfs file
with the same name of an existing one.  This makes the automated testing
tools a lot harder to find the real bugs in the kernel.

So just print a warning out and dump the stack to get the attention of
the developer that they did something foolish.  Then keep on trucking,
as this should not be a fatal error at all.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

Dmitry, does this look good to you?  If so, I'll queue it up for
4.16-rc1.

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 2b67bda2021b..3a36a48a4b3f 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c

@@ -10,6 +10,7 @@
  * Please see Documentation/filesystems/sysfs.txt for more information.
  */
 
+#define pr_fmt(fmt)	"sysfs: " fmt
 #undef DEBUG
 
 #include <linux/fs.h>

@@ -27,8 +28,8 @@ void sysfs_warn_dup(struct kernfs_node *parent, const char *name)
 	if (buf)
 		kernfs_path(parent, buf, PATH_MAX);
 
-	WARN(1, KERN_WARNING "sysfs: cannot create duplicate filename '%s/%s'\n",
-	     buf, name);
+	pr_warn("cannot create duplicate filename '%s/%s'\n", buf, name);
+	dump_stack();
 
 	kfree(buf);
 }