Louis Rilling wrote: > On 04/09/09 10:26 -0500, Serge E. Hallyn wrote: >> Quoting Oren Laadan (orenl@xxxxxxxxxxx): >>> 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)? > > As far as I am concerned, I do have a preference for the ptmx_create() > approach. This task->required_id field reminds me the former approach taken for > restarting pids and (and SYSV IPC ids IIRC) from userspace, that was proposed > last year and actually deemed unacceptable [ IIRC, this was an argument in favor > of a restart() syscall ]. I know that it's not the same since ->required_id is > not set from userspace and used in a later syscall, but still ... > > Moreover I see no reason whey there would be no way to refactorize ptmx code and > have less duplicated code with the ptmx_create() approach. I basically agree - I simply took the easiest/fastest path; if the ptmx code is properly refactored, we should use that instead. Did you have a chance to look at Serge's attempt to do exactly that ? https://lists.linux-foundation.org/pipermail/containers/2009-September/020363.html Thanks, Oren. _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
