Re: [PATCH 0/22] fsnotify: Avoid SRCU stalls with fanotify permission events

Hello, currently, fanotify waits for response to a permission even from userspace process while holding fsnotify_mark_srcu lock. That has a consequence that when userspace process takes long to respond or does not respond at all, fsnotify_mark_srcu period cannot ever complete blocking reclaim of any notification marks and also blocking any process that did synchronize_srcu() on fsnotify_mark_srcu. Effectively, this eventually blocks anybody interacting with the notification subsystem. Miklos has some real world reports of this happening. Although this in principle a problem of broken userspace application (which futhermore has to have CAP_SYS_ADMIN in init_user_ns, so it is not a security problem), it is still nasty that a simple error can block the kernel like this. This patch set solves this problem ... Patches have survived testing with inotify/fanotify tests in LTP. I didn't test audit - Paul can you give these patches some testing? Since some of the changes are really non-trivial, I'd welcome if someone reviewed the patch set.