Hi all, we've made some nice progress on converting code that modifies user memory to the pin_user_pages interface, especially though the work from David Howells on iov_iter_extract_pages. This thread tries to coordinate on how to finish off this work. The obvious next step is the remaining users of iov_iter_get_pages2 and iov_iter_get_pages_alloc2. We have three file system direct I/O users of those left: ceph, fuse and nfs. Lei Huang has sent patches to convert fuse to iov_iter_extract_pages which I'd love to see merged, and we'd need equivalent work for ceph and nfs. The non-file system uses are in the vmsplice code, which only reads from the pages (but would still benefit from an iov_iter_extract_pages conversion), and in net. Out of the users in net, all but the 9p code appear to be for reads from memory, so they don't pin even if a conversion would be nice to retire iov_iter_get_pages* APIs. After that we might have to do an audit of the raw get_user_pages APIs, but there probably aren't many that modify file backed memory. I'm also wondering what a good debug aid would be for detecting writes to file backed memory without a previous reservation, but everything either involves a page flag or file system code. But if someone has an idea I'm all ear as something mechanical to catch these uses would be quite helpful.
