staging/lustre: silence lockdep warning in ll_md_blocking_ast

Got bellow lockdep warning during tests. It is false alarm though.

[ 1184.479097] =============================================
[ 1184.479187] [ INFO: possible recursive locking detected ]
[ 1184.479277] 3.10.0-rc3+ #13 Tainted: G         C
[ 1184.479355] ---------------------------------------------
[ 1184.479444] mkdir/2215 is trying to acquire lock:
[ 1184.479521]  (&(&dentry->d_lock)->rlock){+.+...}, at: [<ffffffffa06cc27c>] ll_md_blocking_ast+0x55c/0x655 [lustre]
[ 1184.479801]
but task is already holding lock:
[ 1184.479895]  (&(&dentry->d_lock)->rlock){+.+...}, at: [<ffffffffa06cc1b1>] ll_md_blocking_ast+0x491/0x655 [lustre]
[ 1184.480101]
other info that might help us debug this:
[ 1184.480206]  Possible unsafe locking scenario:

[ 1184.480300]        CPU0
[ 1184.480340]        ----
[ 1184.480380]   lock(&(&dentry->d_lock)->rlock);
[ 1184.480458]   lock(&(&dentry->d_lock)->rlock);
[ 1184.480536]
 *** DEADLOCK ***

[ 1184.480761]  May be due to missing lock nesting notation

[ 1184.480936] 4 locks held by mkdir/2215:
[ 1184.481037]  #0:  (sb_writers#11){.+.+.+}, at: [<ffffffff811531a9>] mnt_want_write+0x24/0x4b
[ 1184.481273]  #1:  (&type->i_mutex_dir_key#3/1){+.+.+.}, at: [<ffffffff81144fce>] kern_path_create+0x8c/0x144
[ 1184.481513]  #2:  (&sb->s_type->i_lock_key#19){+.+...}, at: [<ffffffffa06cc180>] ll_md_blocking_ast+0x460/0x655 [lustre]
[ 1184.481778]  #3:  (&(&dentry->d_lock)->rlock){+.+...}, at: [<ffffffffa06cc1b1>] ll_md_blocking_ast+0x491/0x655 [lustre]
[ 1184.482050]

Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/llite/dcache.c

@@ -303,7 +303,7 @@ void ll_invalidate_aliases(struct inode *inode)
 			libcfs_debug_dumpstack(NULL);
 		}
 
-		d_lustre_invalidate(dentry);
+		d_lustre_invalidate(dentry, 0);
 	}
 	ll_unlock_dcache(inode);
 

drivers/staging/lustre/lustre/llite/file.c

@@ -2563,7 +2563,7 @@ int __ll_inode_revalidate_it(struct dentry *dentry, struct lookup_intent *it,
 		   here to preserve get_cwd functionality on 2.6.
 		   Bug 10503 */
 		if (!dentry->d_inode->i_nlink)
-			d_lustre_invalidate(dentry);
+			d_lustre_invalidate(dentry, 0);
 
 		ll_lookup_finish_locks(&oit, dentry);
 	} else if (!ll_have_md_lock(dentry->d_inode, &ibits, LCK_MINMODE)) {

drivers/staging/lustre/lustre/llite/llite_internal.h

@@ -1525,13 +1525,14 @@ static inline void __d_lustre_invalidate(struct dentry *dentry)
  * ll_md_blocking_ast), unhash this dentry, and let dcache to reclaim it later;
  * else dput() of the last refcount will unhash this dentry and kill it.
  */
-static inline void d_lustre_invalidate(struct dentry *dentry)
+static inline void d_lustre_invalidate(struct dentry *dentry, int nested)
 {
 	CDEBUG(D_DENTRY, "invalidate dentry %.*s (%p) parent %p inode %p "
 	       "refc %d\n", dentry->d_name.len, dentry->d_name.name, dentry,
 	       dentry->d_parent, dentry->d_inode, d_refcount(dentry));
 
-	spin_lock(&dentry->d_lock);
+	spin_lock_nested(&dentry->d_lock,
+			 nested ? DENTRY_D_LOCK_NESTED : DENTRY_D_LOCK_NORMAL);
 	__d_lustre_invalidate(dentry);
 	if (d_refcount(dentry) == 0)
 		__d_drop(dentry);

drivers/staging/lustre/lustre/llite/namei.c

@@ -187,7 +187,7 @@ static void ll_invalidate_negative_children(struct inode *dir)
 						 &dentry->d_subdirs,
 						 d_u.d_child) {
 				if (child->d_inode == NULL)
-					d_lustre_invalidate(child);
+					d_lustre_invalidate(child, 1);
 			}
 		}
 		spin_unlock(&dentry->d_lock);