On Thu, 11 Jun 2015 15:21:30 -0400 Eric B Munson <emunson@xxxxxxxxxx> wrote: > > Ditto mlockall(MCL_ONFAULT) followed by munlock(). I'm not sure > > that even makes sense but the behaviour should be understood and > > tested. > > I have extended the kselftest for lock-on-fault to try both of these > scenarios and they work as expected. The VMA is split and the VM > flags are set appropriately for the resulting VMAs. munlock() should do vma merging as well. I *think* we implemented that. More tests for you to add ;) How are you testing the vma merging and splitting, btw? Parsing the profcs files? > > What's missing here is a syscall to set VM_LOCKONFAULT on an > > arbitrary range of memory - mlock() for lock-on-fault. It's a > > shame that mlock() didn't take a `mode' argument. Perhaps we > > should add such a syscall - that would make the mmap flag unneeded > > but I suppose it should be kept for symmetry. > > Do you want such a system call as part of this set? I would need some > time to make sure I had thought through all the possible corners one > could get into with such a call, so it would delay a V3 quite a bit. > Otherwise I can send a V3 out immediately. I think the way to look at this is to pretend that mm/mlock.c doesn't exist and ask "how should we design these features". And that would be: - mmap() takes a `flags' argument: MAP_LOCKED|MAP_LOCKONFAULT. - mlock() takes a `flags' argument. Presently that's MLOCK_LOCKED|MLOCK_LOCKONFAULT. - munlock() takes a `flags' arument. MLOCK_LOCKED|MLOCK_LOCKONFAULT to specify which flags are being cleared. - mlockall() and munlockall() ditto. IOW, LOCKED and LOCKEDONFAULT are treated identically and independently. Now, that's how we would have designed all this on day one. And I think we can do this now, by adding new mlock2() and munlock2() syscalls. And we may as well deprecate the old mlock() and munlock(), not that this matters much. *should* we do this? I'm thinking "yes" - it's all pretty simple boilerplate and wrappers and such, and it gets the interface correct, and extensible. What do others think?
