ext4: Fix BUG_ON at fs/buffer.c:652 in no journal mode

Calls to ext4_handle_dirty_metadata should only pass in an inode
pointer for inode-specific metadata, and not for shared metadata
blocks such as inode table blocks, block group descriptors, the
superblock, etc.

The BUG_ON can get tripped when updating a special device (such as a
block device) that is opened (so that i_mapping is set in
fs/block_dev.c) and the file system is mounted in no journal mode.

Addresses-Google-Bug: #2404870

Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 536067b..ecac8c5 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5120,7 +5120,7 @@
 					EXT4_FEATURE_RO_COMPAT_LARGE_FILE);
 			sb->s_dirt = 1;
 			ext4_handle_sync(handle);
-			err = ext4_handle_dirty_metadata(handle, inode,
+			err = ext4_handle_dirty_metadata(handle, NULL,
 					EXT4_SB(sb)->s_sbh);
 		}
 	}
@@ -5149,7 +5149,7 @@
 	}
 
 	BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
-	rc = ext4_handle_dirty_metadata(handle, inode, bh);
+	rc = ext4_handle_dirty_metadata(handle, NULL, bh);
 	if (!err)
 		err = rc;
 	ext4_clear_inode_state(inode, EXT4_STATE_NEW);
@@ -5701,7 +5701,7 @@
 			err = jbd2_journal_get_write_access(handle, iloc.bh);
 			if (!err)
 				err = ext4_handle_dirty_metadata(handle,
-								 inode,
+								 NULL,
 								 iloc.bh);
 			brelse(iloc.bh);
 		}