Overview of v2: Patch 1/7 adds logic to write fastpath handlers in kernel modules. Patch 2/7 adds a sample of a fastpath handler in a kernel module. Patch 3/7 to 5/7 are preparation work on BPF side. Patch 6/7 adds logic to write fastpath handlers in bpf programs. Patch 7/7 is a selftest and example of bpf based fastpath handler. Changes v1 => v2: 1. Add sysfs entries for fastpath handler. 2. Rewrite the sample and bpf selftest to handle subtree monitoring. This requires quite some work from BPF side to properly handle inode, dentry, etc. 3. Add CONFIG_FANOTIFY_FASTPATH. 4. Add more documents. TODO of v2: 1. Enable prviate (not added to global list) bpf based fastpath handlers. 4. Man pages.
