[CRIU] Re: [PATCH] service-fd: Rework it to use in hight performance code

[Cyrill Gorcunov]

On Fri, Sep 07, 2012 at 04:57:54PM +0400, Pavel Emelyanov wrote:
> On 09/07/2012 04:44 PM, Cyrill Gorcunov wrote:
> > On Fri, Sep 07, 2012 at 04:38:21PM +0400, Pavel Emelyanov wrote:
> >>> +
> >>> +int is_service_fd(int fd, int type)
> >>> +{
> >>> +	if (type > SERVICE_FD_OFF_MIN)
> >>> +		return fd == get_service_fd(type);
> >>> +
> >>> +	return fd > service_fd_rlim_min;
> >>
> >> int is_service_fd(int fd)
> >> {
> >> 	return fd > serice_fd_rlim_cur - SERVICE_FD_OFF_MAX;
> >> }
> >>
> > 
> > Pavel, this is not enough for my tty restore code. For control
> > terminals I need to know that fd _is_ CTL_TTY_OFF, not just arbitrary
> > fd from service range. What happen when we need some other service fd
> > in file engine?
> > 
> > Lets do a deal: two helpers
> > 
> > is_any_service_fd(int fd)
> > {
> > 	return fd > serice_fd_rlim_cur - SERVICE_FD_OFF_MAX;
> > }
> > 
> > is_service_fd(int fd, int type)
> > {
> > 	return fd == get_service_fd(type);
> > }
> > 
> > agreed?
> 
> No. You want to have an ability to check that fd is any service by

What I really need is to check that fd is service file descriptor
with mandatory type. I added this _any-fd_ case only because you
were insisting on form like

	return fd > serice_fd_rlim_cur - SERVICE_FD_OFF_MAX;

which is completely useless for my case.

> passing 0 into type? Then write a normal comment about it, not some
> strange hint about "change this MIN carefully".

As to 0 in type -- I think we should simply add BUG_ON here,
since it's not supposed to be called from crtools code with
unknown type.

> 
> And there's no need in TWO global variables _cur and _min.

There is no need, but it eliminates need to do substraction. I'll drop it.

	Cyrill