Function call hierarchy/path since getting the buffer until access its data

Good morning, I am doing a study about buffer management to improve the performance of one program that does heavy I/O operations. After looking and reading from different softwares' source codes/texts one friend suggested me to take a look at the PostgreSQL code. I already took a look at the PostgreSQL buffer management modules ( freelist.c and cia ) but now I am a bit confused how the buffer read/write works, I tried to see how PostgreSQL does to get, for example, a char array from one buffer. Looking at rawpage.c I think that I found a good example using the following function calls sequence starting at function get_raw_page_internal():

But I need more examples or explanations to understand it better. Does anyone have more examples or can recommend me some article that says something about this?

Thanks,
-Waldecir