[PATCH V4 2/6] mm: mlock: Add new mlock, munlock, and munlockall system calls

[emunson@akamai.com (Eric B Munson)]

On Wed, 22 Jul 2015, Michael Ellerman wrote:

> On Tue, 2015-07-21 at 13:44 -0700, Andrew Morton wrote:
> > On Tue, 21 Jul 2015 15:59:37 -0400 Eric B Munson <emunson@akamai.com> wrote:
> > 
> > > With the refactored mlock code, introduce new system calls for mlock,
> > > munlock, and munlockall.  The new calls will allow the user to specify
> > > what lock states are being added or cleared.  mlock2 and munlock2 are
> > > trivial at the moment, but a follow on patch will add a new mlock state
> > > making them useful.
> > > 
> > > munlock2 addresses a limitation of the current implementation.  If a
> > > user calls mlockall(MCL_CURRENT | MCL_FUTURE) and then later decides
> > > that MCL_FUTURE should be removed, they would have to call munlockall()
> > > followed by mlockall(MCL_CURRENT) which could potentially be very
> > > expensive.  The new munlockall2 system call allows a user to simply
> > > clear the MCL_FUTURE flag.
> > 
> > This is hard.  Maybe we shouldn't have wired up anything other than
> > x86.  That's what we usually do with new syscalls.
> 
> Yeah I think so.
> 
> You haven't wired it up properly on powerpc, but I haven't mentioned it because
> I'd rather we did it.
> 
> cheers

It looks like I will be spinning a V5, so I will drop all but the x86
system calls additions in that version.
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