[Devel] Re: [PATCH 2/6] c/r: [pty 1/2] allow allocation of desired pty slave

[Serge E. Hallyn]

Quoting Oren Laadan (orenl at librato.com):
> During restart, we need to allocate pty slaves with the same
> identifiers as recorded during checkpoint. Modify the allocation code
> to allow an in-kernel caller to request a specific slave identifier.
> 
> For this, add a new field to task_struct - 'required_id'. It will
> hold the desired identifier when restoring a (master) pty.
> 
> The code in ptmx_open() will use this value only for tasks that try to
> open /dev/ptmx that are restarting (PF_RESTARTING), and if the value
> isn't CKPT_REQUIRED_NONE (-1).

So noone has indicated any preference for this versus the ptmx_create()
approach...

I'm satisfied knowing we have a working fallback in case task->required_id
is deemed unacceptable.

However I'd like to not have linux-kernel folks think us morons for not
having considered that.  Can you add a message to the changelog saying
why we're going with this approach (namely, that it lets us re-use
filp_open() instead of having to do a custom alloc_file in a new code-path,
which introduces maintenance duplication for file permission checking
paths)?

thanks,
-serge
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