On Wed 04-04-18 10:48:15, Marko Rauhamaa wrote: > Amir Goldstein <amir73il@xxxxxxxxx>: > > The main issue I have right now is with the ignore masks logic. > > The logic in send_to_group() doesn't match the logic in > > fanotify_should_send_event(), which in turn, does not match the man > > page documentation. > > > > I was thinking: > > - ignore mask on inode negates inode and mount and sb mark mask > > - ignore mask on mount negates mount and sb mark masks, but not inode > > mark mask > > - ignore mask on sb negates only sb mark mask > > > > The reasoning is that is makes sense to include a super set and > > exclude a subset. The problem is that inode is not really a subset of > > a mount, but mount and inode are really a subset of a super block. > > > > Current fanotify code seems to allow including an inode, but excluding > > a mount, which will result (I think) in getting events on the inode > > unless it was accessed from a specific mount. The examples of ignore > > mask in the fanotify(7) man page do not imply that this use case was > > intended and I really doubt if anybody is using ignore mask this way. > > > > I wonder if we should change the behavior of fanotify to only allow > > excluding an inode from a mount mark and not vice versa, as suggested > > by man page and by the logic in fsnotify() and send_to_group() and > > wait to see if anybody shouts. > > > > Thoughts? > > First off, adjusting the semantics this way would not affect my > application code in any way. > > However, ... > > 1. What you are proposing is going from include-then-exclude semantics > to big-to-small semantics. Big-to-small semantics are well defined > as long as two entities never partially overlap. That may well be > guaranteed in Linux file systems today, but I wonder if that > assumption can be cast in stone. > > 2. Include-then-exclude semantics is easy to state and understand. It > is also commonplace. Furthermore, I wonder if there was a real need > for reversed, exclude-then-include semantics. You can always set up > a second fanotify fd to monitor the exceptional includes. > > 3. This change potentially breaks some user-space applications out > there. Yeah, include-then-exclude semantics looks like a better option to me as well. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
