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

From: Andy Lutomirski
Date: Tue Feb 21 2017 - 13:41:55 EST

On Tue, Feb 21, 2017 at 8:59 AM, Cyrill Gorcunov <gorcunov@xxxxxxxxxx> 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.