Yes, Canada did in fact sell some 234 million bushels of grain to China. Interestingly, trade officials argued that there was no famine in China at the time. These diplomatic reports are available via the Library and Archives of Canada. In a memo titled "The Extent And Impact Of Food Shortages In China," officials in the foreign ministry stated that there was no evidence of famine, even as the sale of wheat was approved. This was after the 9th Plenum of the 8th Central Committee in January of 1961, when the Central Committee decided to begin the reversal of the Great Leap Forward policies. The first announcement of part of the sale by the Canadian government was in February of that same year. You can find the announcement for the sale for 40 million bushels on page 2 of this document from the Dominion Bureau of Statistics. Australia also began exporting wheat to Canada at this time.

The PRC at the time had done a phenomenal job in convincing most foreign onlookers of the success of the Great Leap Forward. They took photos, made films, created propaganda art, and staged entire fields and villages that all gave the impression of plenty and prosperity. Initially, many families sent letters to friends and family in Hong Kong and Macau, or even in Vietnam, Malaysia, Indonesia, etc. to send food supplies. After a while, cadres in rural villages began censoring or outright blocking this mail and often confiscated the sent food supplies, so this one source of information of the true nature of the situation was blocked off after a while. Unfortunately we have no reliable statistics on how much food was sent and how much was confiscated etc. Our understanding of these practices are based on firsthand interviews.

In fact, during most of the famine China remained a net exporter of grain to pay off its debt obligations to other nations, particularly the Soviet Union. From the outside it really did look like there was no famine. For these reasons, most foreign journalists felt they had no reason to doubt these impressions. The PRC was so locked off at the time that even intelligence agencies had no idea that there was any hint of famine, at least until refugees started sneaking into Hong Kong. So it's not unreasonable that the ministry of Canada would also come to the conclusion that there was no evidence of famine, aside from a few unverified eyewitness accounts.

Moreover, it's important to note that many of the rural villages themselves did not know the extent of the famine, and many thought it was simply a local affair. It wasn't until the 80s when villagers were granted more freedom of movement that the breadth of the famine became clear to Chinese citizens and even foreign China experts.

But even today most Chinese citizens have little understanding of the scope of the tragedy, although some Chinese scholars within China have published pieces on the period. One such scholar is Cao Shuji at Shanghai Jiaotong Unviersity and his book The Great Famine: The population of China from 1959-1961. I believe there is an English language version of this in a condensed paper. He and other scholars are able to publish research on the period primarily through concentrated on the results of the famine like population growth and death count, and not on its causes.

Most still blame it on poor weather, and not incredibly poor planning, a inherently destructive system of political incentives, censorship, and completely ineffective agricultural and industrial policies.

The best sources for learning more about the famine and the Great Leap Forward in general are Yang Jisheng's Tombstone and Frank Dikötter's Mao's Great Famine. Yang's is the most heart-wrenching and contains the most firsthand accounts from villagers who suffered during those years. It's not for the faint of heart, but it's a powerful piece of research. The Institutional Causes of China's Great Famine, 1959–1961 by Xin Meng is also really quite good, as is Anthony Garnaut's The Geography of the Great Leap Famine.

Edit: I should note that the document cited above does not state explicitly whether or not it was done on credit. The announcement also notes that representatives had been sent in 1958 and 1960. It's possible that the deal was being negotiated previously or that Chinese authorities had put off purchases. I'd have to dig further to find out more about this specific transaction.