On Tue, 9 Oct 2018 10:30:25 +0200 Jan Kara <jack@xxxxxxx> wrote: > > Also, maintainability. What happens if someone now uses put_page() by > > mistake? Kernel fails in some mysterious fashion? How can we prevent > > this from occurring as code evolves? Is there a cheap way of detecting > > this bug at runtime? > > The same will happen as with any other reference counting bug - the special > user reference will leak. It will be pretty hard to debug I agree. I was > thinking about whether we could provide some type safety against such bugs > such as get_user_pages() not returning struct page pointers but rather some > other special type but it would result in a big amount of additional churn > as we'd have to propagate this different type e.g. through the IO path so > that IO completion routines could properly call put_user_pages(). So I'm > not sure it's really worth it. I'm not really understanding. Patch 3/3 changes just one infiniband driver to use put_user_page(). But the changelogs here imply (to me) that every user of get_user_pages() needs to be converted to s/put_page/put_user_page/. Methinks a bit more explanation is needed in these changelogs?
