Re: [RFC 1/3] procfs: fdinfo -- Extend information about epoll target files

On Tue, Feb 21, 2017 at 8:59 AM, Cyrill Gorcunov [off-list ref] wrote:

Since it is possbile to have same number in tfd field (say
file added, closed, then nother file dup'ed to same number
and added back) it is imposible to distinguish such target
files solely by their numbers.

Strictly speaking regular applications don't need to recognize
these targets at all but for checkpoint/restore sake we need
to collect targets to be able to push them back on restore
in proper order.

Thus lets add file position, inode and device number where
this target lays. This three fields can be used as a primary
key for sorting, and together with kcmp help CRIU can find
out an exact file target (from the whole set of processes
being checkpointed).

I have no problem with this, but I'm wondering whether kcmp's ordered
comparisons could also be used for this purpose.