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>

fs/ext4/ext4_jbd2.c

@@ -125,7 +125,7 @@ int __ext4_handle_dirty_metadata(const char *where, handle_t *handle,
 			ext4_journal_abort_handle(where, __func__, bh,
 						  handle, err);
 	} else {
-		if (inode && bh)
+		if (inode)
 			mark_buffer_dirty_inode(bh, inode);
 		else
 			mark_buffer_dirty(bh);

fs/ext4/ialloc.c

@@ -898,7 +898,7 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode,
 				BUFFER_TRACE(inode_bitmap_bh,
 					"call ext4_handle_dirty_metadata");
 				err = ext4_handle_dirty_metadata(handle,
-								 inode,
+								 NULL,
 							inode_bitmap_bh);
 				if (err)
 					goto fail;

fs/ext4/inode.c

@@ -5120,7 +5120,7 @@ static int ext4_do_update_inode(handle_t *handle,
 					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 @@ static int ext4_do_update_inode(handle_t *handle,
 	}
 
 	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 @@ static int ext4_pin_inode(handle_t *handle, struct inode *inode)
 			err = jbd2_journal_get_write_access(handle, iloc.bh);
 			if (!err)
 				err = ext4_handle_dirty_metadata(handle,
-								 inode,
+								 NULL,
 								 iloc.bh);
 			brelse(iloc.bh);
 		}

fs/ext4/namei.c

@@ -2017,7 +2017,7 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
 	/* Insert this inode at the head of the on-disk orphan list... */
 	NEXT_ORPHAN(inode) = le32_to_cpu(EXT4_SB(sb)->s_es->s_last_orphan);
 	EXT4_SB(sb)->s_es->s_last_orphan = cpu_to_le32(inode->i_ino);
-	err = ext4_handle_dirty_metadata(handle, inode, EXT4_SB(sb)->s_sbh);
+	err = ext4_handle_dirty_metadata(handle, NULL, EXT4_SB(sb)->s_sbh);
 	rc = ext4_mark_iloc_dirty(handle, inode, &iloc);
 	if (!err)
 		err = rc;
@@ -2089,7 +2089,7 @@ int ext4_orphan_del(handle_t *handle, struct inode *inode)
 		if (err)
 			goto out_brelse;
 		sbi->s_es->s_last_orphan = cpu_to_le32(ino_next);
-		err = ext4_handle_dirty_metadata(handle, inode, sbi->s_sbh);
+		err = ext4_handle_dirty_metadata(handle, NULL, sbi->s_sbh);
 	} else {
 		struct ext4_iloc iloc2;
 		struct inode *i_prev =