Commentary for Berakhot 74:7

Since there are no pieces the size of an olive.

I.e. the benediction is unnecessary.

According to Rashi this refers to the cmmbs of the meal-offering. But Tosafot object that this cannot be, because it continaes "should it be leaven"; and the meal-offering must be unleaven. Consequently it is taken to refer to crumbs of different species, each in itself not the size of an olive.

By eating them on Passover.

When it is his duty to eat unleaven. Consequently these crumbs are together considered to be equivalent to a piece of the size of an olive, otherwise he would not be violating the Passover if they were leaven, or fulfil the law of the Passover if unleaven.