Compressed files & the page cache

[Matthew Wilcox]

I've started looking at how the page cache can help filesystems handle
compressed data better.  Feedback would be appreciated!  I'll probably
say a few things which are obvious to anyone who knows how compressed
files work, but I'm trying to be explicit about my assumptions.

First, I believe that all filesystems work by compressing fixed-size
plaintext into variable-sized compressed blocks.  This would be a good
point to stop reading and tell me about counterexamples.