On Fri, Jul 24, 2015 at 05:28:42PM -0400, Eric B Munson wrote:

The previous patch introduced a flag that specified pages in a VMA
should be placed on the unevictable LRU, but they should not be made
present when the area is created.  This patch adds the ability to set
this state via the new mlock system calls.

We add MLOCK_ONFAULT for mlock2 and MCL_ONFAULT for mlockall.
MLOCK_ONFAULT will set the VM_LOCKONFAULT flag as well as the VM_LOCKED
flag for the target region.  MCL_CURRENT and MCL_ONFAULT are used to
lock current mappings.  With MCL_CURRENT all pages are made present and
with MCL_ONFAULT they are locked when faulted in.  When specified with
MCL_FUTURE all new mappings will be marked with VM_LOCKONFAULT.

Currently, mlockall() clears all VMA lock flags and then sets the
requested flags.  For instance, if a process has MCL_FUTURE and
MCL_CURRENT set, but they want to clear MCL_FUTURE this would be
accomplished by calling mlockall(MCL_CURRENT).  This still holds with
the introduction of MCL_ONFAULT.  Each call to mlockall() resets all
VMA flags to the values specified in the current call.  The new mlock2
system call behaves in the same way.  If a region is locked with
MLOCK_ONFAULT and a user wants to force it to be populated now, a second
call to mlock2(MLOCK_LOCKED) will accomplish this.

munlock() will unconditionally clear both vma flags.  munlockall()
unconditionally clears for VMA flags on all VMAs and in the
mm->def_flags field.

Signed-off-by: Eric B Munson <redacted>
Cc: Michal Hocko <redacted>
Cc: Vlastimil Babka <redacted>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Kirill A. Shutemov" <redacted>
Cc: linux-alpha@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: sparclinux@vger.kernel.org
Cc: linux-xtensa@linux-xtensa.org
Cc: linux-arch@vger.kernel.org
Cc: linux-api@vger.kernel.org
Cc: linux-mm@kvack.org
---
Changes from V4:
* Split addition of VMA flag

Changes from V3:
* Do extensive search for VM_LOCKED and ensure that VM_LOCKONFAULT is also handled
 where appropriate
 arch/alpha/include/uapi/asm/mman.h   |  2 ++
 arch/mips/include/uapi/asm/mman.h    |  2 ++
 arch/parisc/include/uapi/asm/mman.h  |  2 ++
 arch/powerpc/include/uapi/asm/mman.h |  2 ++
 arch/sparc/include/uapi/asm/mman.h   |  2 ++
 arch/tile/include/uapi/asm/mman.h    |  3 +++
 arch/xtensa/include/uapi/asm/mman.h  |  2 ++

Again, you can save few lines by moving some code into mman-common.h.

Otherwise looks good.

-- 
 Kirill A. Shutemov

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>