Re: [PATCH] userfaultfd_zeropage: return -ENOSPC in case mm has gone

From: Mike Rapoport
Date: Thu Aug 03 2017 - 13:26:02 EST

On Wed, Aug 02, 2017 at 06:40:01PM +0200, Andrea Arcangeli wrote:
> On Wed, Aug 02, 2017 at 06:22:49PM +0200, Michal Hocko wrote:
> > ESRCH refers to "no such process". Strictly speaking userfaultfd code is
> > about a mm which is gone but that is a mere detail. In fact the owner of
> Well this whole issue about which retval, is about a mere detail in
> the first place, so I don't think you can discount all other mere
> details as irrelevant in the evaluation of a change to solve a mere
> detail.
> > But as I've said, this might be really risky to change. My impression
> > was that userfaultfd is not widely used yet and those can be fixed
> > easily but if that is not the case then we have to live with the current
> The only change would be for userfaultfd non cooperative mode, and
> CRIU is the main user of that. So I think it is up to Mike to decide,
> I'm fine either ways. I certainly agree ESRCH could be a slightly
> better fit, I only wanted to clarify it's not a 100% match either.

I'm Ok with updating the code and the man page as long as Michal takes the
blame if anything but CRIU breaks :)

Now, seriously, I believe there are not many users of non-cooperative uffd
if at all and it is very unlikely anybody has it in production.

I'll send a patch with s/ENOSPC/ESRCH in the next few days.

Sincerely yours,