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>

fs/ceph/dir.c

@@ -507,7 +507,7 @@ static loff_t ceph_dir_llseek(struct file *file, loff_t offset, int whence)
 	loff_t old_offset = ceph_make_fpos(fi->frag, fi->next_offset);
 	loff_t retval;
 
-	mutex_lock(&inode->i_mutex);
+	inode_lock(inode);
 	retval = -EINVAL;
 	switch (whence) {
 	case SEEK_CUR:
@@ -542,7 +542,7 @@ static loff_t ceph_dir_llseek(struct file *file, loff_t offset, int whence)
 		}
 	}
 out:
-	mutex_unlock(&inode->i_mutex);
+	inode_unlock(inode);
 	return retval;
 }