ext3 -nobh option causes oops

For files other than IFREG, nobh option doesn't make sense.  Modifications
to them are journalled and needs buffer heads to do that.  Without this
patch, we get kernel oops in page_buffers().
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>

fs/ext3/inode.c

@@ -1005,7 +1005,7 @@ static int ext3_prepare_write(struct file *file, struct page *page,
 		ret = PTR_ERR(handle);
 		goto out;
 	}
-	if (test_opt(inode->i_sb, NOBH))
+	if (test_opt(inode->i_sb, NOBH) && ext3_should_writeback_data(inode))
 		ret = nobh_prepare_write(page, from, to, ext3_get_block);
 	else
 		ret = block_prepare_write(page, from, to, ext3_get_block);
@@ -1093,7 +1093,7 @@ static int ext3_writeback_commit_write(struct file *file, struct page *page,
 	if (new_i_size > EXT3_I(inode)->i_disksize)
 		EXT3_I(inode)->i_disksize = new_i_size;
 
-	if (test_opt(inode->i_sb, NOBH))
+	if (test_opt(inode->i_sb, NOBH) && ext3_should_writeback_data(inode))
 		ret = nobh_commit_write(file, page, from, to);
 	else
 		ret = generic_commit_write(file, page, from, to);
@@ -1343,7 +1343,7 @@ static int ext3_writeback_writepage(struct page *page,
 		goto out_fail;
 	}
 
-	if (test_opt(inode->i_sb, NOBH))
+	if (test_opt(inode->i_sb, NOBH) && ext3_should_writeback_data(inode))
 		ret = nobh_writepage(page, ext3_get_block, wbc);
 	else
 		ret = block_write_full_page(page, ext3_get_block, wbc);