On Wed, 08 Jul 2015, Jonathan Corbet wrote: > On Wed, 8 Jul 2015 16:34:56 -0400 > Eric B Munson <emunson@xxxxxxxxxx> wrote: > > > > Quick, possibly dumb question: I've been beating my head against these for > > > a little bit, and I can't figure out what's supposed to happen in this > > > case: > > > > > > mlock2(addr, len, MLOCK_ONFAULT); > > > munlock2(addr, len, MLOCK_LOCKED); > > > > > > It looks to me like it will clear VM_LOCKED without actually unlocking any > > > pages. Is that the intended result? > > > > This is not quite right, what happens when you call munlock2(addr, len, > > MLOCK_LOCKED); is we call apply_vma_flags(addr, len, VM_LOCKED, false). > > From your explanation, it looks like what I said *was* right...what I was > missing was the fact that VM_LOCKED isn't set in the first place. So that > call would be a no-op, clearing a flag that's already cleared. Sorry, I misread the original. You are correct with the addition that the call to munlock2(MLOCK_LOCKED) is a noop in this case. > > One other question...if I call mlock2(MLOCK_ONFAULT) on a range that > already has resident pages, I believe that those pages will not be locked > until they are reclaimed and faulted back in again, right? I suspect that > could be surprising to users. That is the case. I am looking into what it would take to find only the present pages in a range and lock them, if that is the behavior that is preferred I can include it in the updated series. > > Thanks, > > jon
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