New code for 5.9: - Make sure we call ->iomap_end with a failure code if ->iomap_begin failed in any way; some filesystems need to try to undo things. - Don't invalidate the page cache during direct reads since we already sync'd the cache with disk. - Make direct writes fall back to the page cache if the pre-write cache invalidation fails. This avoids a cache coherency problem. - Fix some idiotic virus scanner warning bs in the previous tag.