Extend open_files

[tijko]

This allows for tracking of anonymous inodes and also adds a field for mnt_id inside of popenfile.

mnt_id This field, present since Linux 3.15, is the ID of the
mount point containing this file. See the description
of /proc/[pid]/mountinfo

[tijko]

Added the mnt_id field and a anon_fields which defaults to an empty dict if a regular file.

[giampaolo]

What's the use case for this? What's an anonymous file? What's a mnt_id? You're introducing a difference in term of API for one platform, so it must be worth it.

[tijko]

Anonymous files are open files that don't have corresponding inodes (i.e. they do not have a path on the filesystem). Examples of these would be created using epoll_create, inotify_init, signalfd, eventfd, and others. Nevertheless, there is still very useful data that is contained in their respective /proc/$pid/fdinfo entries. For instance, if a process had numerous fd's being monitored by an epoll fd, you can then see which events were masked into said poll. Another use (and the one that I had been needing) would be if you have an inotify fd in a process and needed to see what the inode of contained watch is, you would be able to find this under the inotifys ino field.

The mnt_id has been exposed since Linux 3.15. The mnt_id is needed when a there are two file descriptors with the same path but, are on different mount points with separate namespaces.

There was definitely more that could have been included in this commit but, I felt as though I wanted to see how you felt about this kind of change first before adding more into it.

[a-sk]

I would like to see mountinfo information for a given process.

[giampaolo]

Closing this out as outdated.