kernfs: make kernfs_deactivate() honor KERNFS_LOCKDEP flag

kernfs_deactivate() forgot to check whether KERNFS_LOCKDEP is set
before performing lockdep annotations and ends up feeding
uninitialized lockdep_map to lockdep triggering warning like the
following on USB stick hotunplug.

 usb 1-2: USB disconnect, device number 2
 INFO: trying to register non-static key.
 the code is fine but needs lockdep annotation.
 turning off the locking correctness validator.
 CPU: 1 PID: 62 Comm: khubd Not tainted 3.13.0-work+ #82
 Hardware name: empty empty/S3992, BIOS 080011  10/26/2007
  ffff880065ca7f60 ffff88013a4ffa08 ffffffff81cfb6bd 0000000000000002
  ffff88013a4ffac8 ffffffff810f8530 ffff88013a4fc710 0000000000000002
  ffff880100000000 ffffffff82a3db50 0000000000000001 ffff88013a4fc710
 Call Trace:
  [<ffffffff81cfb6bd>] dump_stack+0x4e/0x7a
  [<ffffffff810f8530>] __lock_acquire+0x1910/0x1e70
  [<ffffffff810f931a>] lock_acquire+0x9a/0x1d0
  [<ffffffff8127c75e>] kernfs_deactivate+0xee/0x130
  [<ffffffff8127d4c8>] kernfs_addrm_finish+0x38/0x60
  [<ffffffff8127d701>] kernfs_remove_by_name_ns+0x51/0xa0
  [<ffffffff8127b4f1>] remove_files.isra.1+0x41/0x80
  [<ffffffff8127b7e7>] sysfs_remove_group+0x47/0xa0
  [<ffffffff8127b873>] sysfs_remove_groups+0x33/0x50
  [<ffffffff8177d66d>] device_remove_attrs+0x4d/0x80
  [<ffffffff8177e25e>] device_del+0x12e/0x1d0
  [<ffffffff819722c2>] usb_disconnect+0x122/0x1a0
  [<ffffffff819749b5>] hub_thread+0x3c5/0x1290
  [<ffffffff810c6a6d>] kthread+0xed/0x110
  [<ffffffff81d0a56c>] ret_from_fork+0x7c/0xb0

Fix it by making kernfs_deactivate() perform lockdep annotations only
if KERNFS_LOCKDEP is set.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Fabio Estevam <festevam@gmail.com>
Reported-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Jiri Kosina <jkosina@suse.cz>
Reported-by: Dave Jones <davej@redhat.com>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 4 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 5104cf5d25c5..bd6e18be6e1a 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -187,19 +187,23 @@ static void kernfs_deactivate(struct kernfs_node *kn)
 
         kn->u.completion = (void *)&wait;
 
-        rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
+        if (kn->flags & KERNFS_LOCKDEP)
+                rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
         /* atomic_add_return() is a mb(), put_active() will always see
          * the updated kn->u.completion.
          */
         v = atomic_add_return(KN_DEACTIVATED_BIAS, &kn->active);
 
         if (v != KN_DEACTIVATED_BIAS) {
-                lock_contended(&kn->dep_map, _RET_IP_);
+                if (kn->flags & KERNFS_LOCKDEP)
+                        lock_contended(&kn->dep_map, _RET_IP_);
                 wait_for_completion(&wait);
         }
 
-        lock_acquired(&kn->dep_map, _RET_IP_);
-        rwsem_release(&kn->dep_map, 1, _RET_IP_);
+        if (kn->flags & KERNFS_LOCKDEP) {
+                lock_acquired(&kn->dep_map, _RET_IP_);
+                rwsem_release(&kn->dep_map, 1, _RET_IP_);
+        }
 }
 
 /**