static enum count_type __read_io_type(struct page *page)
{
	struct address_space *mapping = page->mapping;

	if (mapping) {
		struct inode *inode = mapping->host;
		struct f2fs_sb_info *sbi = F2FS_I_SB(inode);

		if (inode->i_ino == F2FS_META_INO(sbi))
			return F2FS_RD_META;

		if (inode->i_ino == F2FS_NODE_INO(sbi))
			return F2FS_RD_NODE;
	}
	return F2FS_RD_DATA;
}
A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.