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/9p/vfs_file.c b/fs/9p/vfs_file.c
index 7bf835f..eadc894 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -449,14 +449,14 @@
 	if (retval)
 		return retval;
 
-	mutex_lock(&inode->i_mutex);
+	inode_lock(inode);
 	p9_debug(P9_DEBUG_VFS, "filp %p datasync %x\n", filp, datasync);
 
 	fid = filp->private_data;
 	v9fs_blank_wstat(&wstat);
 
 	retval = p9_client_wstat(fid, &wstat);
-	mutex_unlock(&inode->i_mutex);
+	inode_unlock(inode);
 
 	return retval;
 }
@@ -472,13 +472,13 @@
 	if (retval)
 		return retval;
 
-	mutex_lock(&inode->i_mutex);
+	inode_lock(inode);
 	p9_debug(P9_DEBUG_VFS, "filp %p datasync %x\n", filp, datasync);
 
 	fid = filp->private_data;
 
 	retval = p9_client_fsync(fid, datasync);
-	mutex_unlock(&inode->i_mutex);
+	inode_unlock(inode);
 
 	return retval;
 }