[$] The intersection of unstable pages and direct I/O

Longtime LWN readers will have encountered the concept of "stable pages"before; it was first covered here nearly15years ago. For the most part, the problem that stable pages weremeant to solve - preventing errors when user space modifies a buffer thatis under I/O - has been dealt with. Butrecent discussions show that there is one area where problems remain:direct I/O. There is some disagreement,though, over whether those problems are the result of user-space bugs andhow much of a performance price should be paid to address them.