Linux: Add support for fanotify when available (running as root)

[mat-sz]

In theory, this should allow for a more efficient way to watch entire filesystems without hitting the watch limits on Linux. I've seen this requested a few times in unrelated issues (mostly VSCode). This only works when running as root.

Let me know if this is something you'd be interested integrating into your project. Lacks unit tests since I'm not sure if this is going to be the final implementation of this.

[mat-sz]

All the tests are passing locally, running sudo yarn test will result in fanotify_* being used instead of inotify_* on Linux as predicted.

[mat-sz]

@ianhattendorf Since I believe you might be the maintainer here, could you take a look? Thanks in advance.

[ianhattendorf]

Requiring root is a pretty big limitation. Also, what happens on kernels prior to 5.1? See failing centos test. Since most distributed binaries on Linux will be compiled for the lowest common denominator, it might not make much sense to support this until most applications only support kernel 5.1+.

In particular, there was no support for create, delete, and move events. The support for those events was added in Linux 5.1.

[mat-sz]

@ianhattendorf

Requiring root is a pretty big limitation.

I'm working on a Linux service that indexes the hard drive, so in this case it's not completely useless. But I agree with you here, 99% of users won't be able to utilize this.

Just wanted to contribute this in case someone else ends up with a similar use case.

Also, what happens on kernels prior to 5.1? See failing centos test. Since most distributed binaries on Linux will be compiled for the lowest common denominator, it might not make much sense to support this until most applications only support kernel 5.1+.

In particular, there was no support for create, delete, and move events. The support for those events was added in Linux 5.1.

I could disable the code paths for kernels that don't support those events. The issue with prebuilt binaries still remains though.

On the other hand, if this isn't something you'd be interested in - I'm going to create a fork with support for this.

[ianhattendorf]

I think a fork would probably be best at this point for such a niche case. Thanks you for checking to see if we would be interested though 👍