Quoting Greg Kurz (gkurz@xxxxxxxxxx): > 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. I'm sure Dave understood that this was possible :) But what you and Alexey are proposing does not and cannot fullfill Ingo's requirement. -serge _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
