To understand what the issue is, we must first gain a bit of a deeper understanding of how the I/O code path actually works; the following diagram encapsulates the points of relevance:
Figure 1: Page cache populated with
disk data
The reader should realize that though this diagram seems quite detailed, we're actually seeing a rather simplistic view of the entire Linux I/O code path (or I/O stack), only what is relevant to this discussion. For a more detailed overview (and diagram), please see the link provided in the Further reading section on the GitHub repository.
Let's say that a Process P1 intends to read ...
