wrappers for ->i_mutex access

parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).

Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/dcache.c b/fs/dcache.c
index b4539e8..92d5140 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2462,7 +2462,7 @@
  */
 void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
 {
-	BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));
+	BUG_ON(!inode_is_locked(dentry->d_parent->d_inode));
 	BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
 
 	spin_lock(&dentry->d_lock);
@@ -2738,7 +2738,7 @@
 	if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
 		goto out_err;
 	m1 = &dentry->d_sb->s_vfs_rename_mutex;
-	if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
+	if (!inode_trylock(alias->d_parent->d_inode))
 		goto out_err;
 	m2 = &alias->d_parent->d_inode->i_mutex;
 out_unalias: