On Fri, 2009-03-06 at 01:00 +0300, Alexey Dobriyan wrote: > On Thu, Mar 05, 2009 at 01:27:07PM -0800, Dave Hansen wrote: > > > Imagine, unsupported file is opened between userspace checks > > > for /proc/*/checkpointable and /proc/*/fdinfo/*/checkpointable > > > and whatever, you stil have to do all the checks inside checkpoint(2). > > > > Alexey, we have two problems here. I completely agree that we have to > > do complete and thorough checks of each file descriptor at > > sys_checkpoint(). Any checks made at other times should not be trusted. > > > > The other side is what Ingo has been asking for. How do we *know* when > > we are checkpointable *before* we call (and without calling) > > This "without calling checkpoint(2)" results in much complications > as demonstrated. > > task_struct and file are not like other structures because they are exposed > in /proc. For PROC_FS=n kernels, one can't even check. > > You can do checkpoint(2) without actual dump. You pass, you're most > certainly checkpointable (with inevitable race condition in mind). > Ahhh thank you very much Alexey ! I wanted to explain this to Dave a few monthes ago but I failed... probably because of my poor English skills. https://lists.linux-foundation.org/pipermail/containers/2008-October/013549.html Why would we add checking all over the place when it MUST be done on the sys_checkpoint() path ? The checkpoint(2) dry-run is definitely the way to go. > With time the amount of stuff C/R won't support will approach zero, > but the infrastructure for "checkpointable" will stay constant. > If it's too much right now, it will be way too much in future. > > > sys_checkpoint()? You are yet to acknowledge that this is a valid use > > case, but it is exactly what Ingo is asking for, I believe. > > It's a valid requirement. > > > If nice printk()s are sufficient to cover what Ingo wants, I'm quite > > happy to remove the /proc files. > _______________________________________________ > Containers mailing list > Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx > https://lists.linux-foundation.org/mailman/listinfo/containers -- Gregory Kurz gkurz@xxxxxxxxxx Software Engineer @ IBM/Meiosys http://www.ibm.com Tel +33 (0)534 638 479 Fax +33 (0)561 400 420 "Anarchy is about taking complete responsibility for yourself." Alan Moore. _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
