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

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Date:	Tue, 21 Jul 2015 13:44:41 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Eric B Munson <emunson@...mai.com>
Cc:	Michal Hocko <mhocko@...e.cz>, Vlastimil Babka <vbabka@...e.cz>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Guenter Roeck <linux@...ck-us.net>,
	linux-alpha@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	adi-buildroot-devel@...ts.sourceforge.net,
	linux-cris-kernel@...s.com, linux-ia64@...r.kernel.org,
	linux-m68k@...r.kernel.org, linux-mips@...ux-mips.org,
	linux-am33-list@...hat.com, linux-parisc@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
	linux-xtensa@...ux-xtensa.org, linux-api@...r.kernel.org,
	linux-arch@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH V4 2/6] mm: mlock: Add new mlock, munlock, and
 munlockall system calls

On Tue, 21 Jul 2015 15:59:37 -0400 Eric B Munson <emunson@...mai.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.

You appear to have missed
mm-mlock-add-new-mlock-munlock-and-munlockall-system-calls-fix.patch:

--- a/arch/arm64/include/asm/unistd.h~mm-mlock-add-new-mlock-munlock-and-munlockall-system-calls-fix
+++ a/arch/arm64/include/asm/unistd.h
@@ -44,7 +44,7 @@
 #define __ARM_NR_compat_cacheflush	(__ARM_NR_COMPAT_BASE+2)
 #define __ARM_NR_compat_set_tls		(__ARM_NR_COMPAT_BASE+5)
 
-#define __NR_compat_syscalls		388
+#define __NR_compat_syscalls		391
 #endif
 
 #define __ARCH_WANT_SYS_CLONE


And mm-mlock-add-new-mlock-munlock-and-munlockall-system-calls-fix-2.patch:


From: Heiko Carstens <heiko.carstens@...ibm.com>
Subject: mm-mlock-add-new-mlock-munlock-and-munlockall-system-calls-fix-2

can we just remove the s390 bits which cause the breakage?
I will wire up the syscalls as soon as the patch set gets merged.

Heiko Carstens <heiko.carstens@...ibm.com>
Cc: Eric B Munson <emunson@...mai.com>
Cc: Stephen Rothwell <sfr@...b.auug.org.au>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 arch/s390/kernel/syscalls.S |    3 ---
 1 file changed, 3 deletions(-)

diff -puN arch/s390/kernel/syscalls.S~mm-mlock-add-new-mlock-munlock-and-munlockall-system-calls-fix-2 arch/s390/kernel/syscalls.S
--- a/arch/s390/kernel/syscalls.S~mm-mlock-add-new-mlock-munlock-and-munlockall-system-calls-fix-2
+++ a/arch/s390/kernel/syscalls.S
@@ -363,6 +363,3 @@ SYSCALL(sys_bpf,compat_sys_bpf)
 SYSCALL(sys_s390_pci_mmio_write,compat_sys_s390_pci_mmio_write)
 SYSCALL(sys_s390_pci_mmio_read,compat_sys_s390_pci_mmio_read)
 SYSCALL(sys_execveat,compat_sys_execveat)
-SYSCALL(sys_mlock2,compat_sys_mlock2)			/* 355 */
-SYSCALL(sys_munlock2,compat_sys_munlock2)
-SYSCALL(sys_munlockall2,compat_sys_munlockall2)


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