[PATCH v5] add MAP_UNLOCKED mmap flag

Gleb Natapov
2010-01-13T09:31:29Z

If application does mlockall(MCL_FUTURE) it is no longer possible to mmap
file bigger than main memory or allocate big area of anonymous memory
in a thread safe manner. Sometimes it is desirable to lock everything
related to program execution into memory, but still be able to mmap
big file or allocate huge amount of memory and allow OS to swap them on
demand. MAP_UNLOCKED allows to do that.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
---

I get reports that people find this useful, so resending.

v1->v2
- adding new flag to all archs
- fixing typo
v2->v3
- one more typo fix
v3->v4
- return error if MAP_LOCKED | MAP_UNLOCKED is specified
v4->v5
- rebase to latest head

diff --git a/arch/alpha/include/asm/mman.h b/arch/alpha/include/asm/mman.h
index 99c56d4..cfc51ac 100644
--- a/arch/alpha/include/asm/mman.h
+++ b/arch/alpha/include/asm/mman.h
@@ -30,6 +30,7 @@
#define MAP_NONBLOCK 0x40000 /* do not block on IO */
#define MAP_STACK 0x80000 /* give out an address that is best suited for process/thread stacks */
#define MAP_HUGETLB 0x100000 /* create a huge page mapping */
+#define MAP_UNLOCKED 0x200000 /* force page unlocking */

#define MS_ASYNC 1 /* sync memory asynchronously */
#define MS_SYNC 2 /* synchronous memory sync */
diff --git a/arch/mips/include/asm/mman.h b/arch/mips/include/asm/mman.h
index c892bfb..3e4d108 100644
--- a/arch/mips/include/asm/mman.h
+++ b/arch/mips/include/asm/mman.h
@@ -48,6 +48,7 @@
#define MAP_NONBLOCK 0x20000 /* do not block on IO */
#define MAP_STACK 0x40000 /* give out an address that is best suited for process/thread stacks */
#define MAP_HUGETLB 0x80000 /* create a huge page mapping */
+#define MAP_UNLOCKED 0x100000 /* force page unlocking */

/*
* Flags for msync
diff --git a/arch/parisc/include/asm/mman.h b/arch/parisc/include/asm/mman.h
index 9749c8a..4e8b9bf 100644
--- a/arch/parisc/include/asm/mman.h
+++ b/arch/parisc/include/asm/mman.h
@@ -24,6 +24,7 @@
#define MAP_NONBLOCK 0x20000 /* do not block on IO */
#define MAP_STACK 0x40000 /* give out an address that is best suited for process/thread stacks */
#define MAP_HUGETLB 0x80000 /* create a huge page mapping */
+#define MAP_UNLOCKED 0x100000 /* force page unlocking */

#define MS_SYNC 1 /* synchronous memory sync */
#define MS_ASYNC 2 /* sync memory asynchronously */
diff --git a/arch/powerpc/include/asm/mman.h b/arch/powerpc/include/asm/mman.h
index d4a7f64..7d33f01 100644
--- a/arch/powerpc/include/asm/mman.h
+++ b/arch/powerpc/include/asm/mman.h
@@ -27,6 +27,7 @@
#define MAP_NONBLOCK 0x10000 /* do not block on IO */
#define MAP_STACK 0x20000 /* give out an address that is best suited for process/thread stacks */
#define MAP_HUGETLB 0x40000 /* create a huge page mapping */
+#define MAP_UNLOCKED 0x80000 /* force page unlocking */

#ifdef __KERNEL__
#ifdef CONFIG_PPC64
diff --git a/arch/sparc/include/asm/mman.h b/arch/sparc/include/asm/mman.h
index c3029ad..f80d203 100644
--- a/arch/sparc/include/asm/mman.h
+++ b/arch/sparc/include/asm/mman.h
@@ -22,6 +22,7 @@
#define MAP_NONBLOCK 0x10000 /* do not block on IO */
#define MAP_STACK 0x20000 /* give out an address that is best suited for process/thread stacks */
#define MAP_HUGETLB 0x40000 /* create a huge page mapping */
+#define MAP_UNLOCKED 0x80000 /* force page unlocking */

#ifdef __KERNEL__
#ifndef __ASSEMBLY__
diff --git a/arch/xtensa/include/asm/mman.h b/arch/xtensa/include/asm/mman.h
index fca4db4..c62bcd8 100644
--- a/arch/xtensa/include/asm/mman.h
+++ b/arch/xtensa/include/asm/mman.h
@@ -55,6 +55,7 @@
#define MAP_NONBLOCK 0x20000 /* do not block on IO */
#define MAP_STACK 0x40000 /* give out an address that is best suited for process/thread stacks */
#define MAP_HUGETLB 0x80000 /* create a huge page mapping */
+#define MAP_UNLOCKED 0x100000 /* force page unlocking */

/*
* Flags for msync
diff --git a/include/asm-generic/mman.h b/include/asm-generic/mman.h
index 32c8bd6..59e0f29 100644
--- a/include/asm-generic/mman.h
+++ b/include/asm-generic/mman.h
@@ -12,6 +12,7 @@
#define MAP_NONBLOCK 0x10000 /* do not block on IO */
#define MAP_STACK 0x20000 /* give out an address that is best suited for process/thread stacks */
#define MAP_HUGETLB 0x40000 /* create a huge page mapping */
+#define MAP_UNLOCKED 0x80000 /* force page unlocking */

#define MCL_CURRENT 1 /* lock all current mappings */
#define MCL_FUTURE 2 /* lock all future mappings */
diff --git a/mm/mmap.c b/mm/mmap.c
index ee22989..4bda220 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -962,6 +962,9 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
if (!can_do_mlock())
return -EPERM;

+ if (flags & MAP_UNLOCKED)
+ vm_flags &= ~VM_LOCKED;
+
/* mlock MCL_FUTURE? */
if (vm_flags & VM_LOCKED) {
unsigned long locked, lock_limit;
@@ -1050,7 +1053,10 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
struct file *file = NULL;
unsigned long retval = -EBADF;

- if (!(flags & MAP_ANONYMOUS)) {
+ if (unlikely((flags & (MAP_LOCKED | MAP_UNLOCKED)) ==
+ (MAP_LOCKED | MAP_UNLOCKED))) {
+ return -EINVAL;
+ } else if (!(flags & MAP_ANONYMOUS)) {
if (unlikely(flags & MAP_HUGETLB))
return -EINVAL;
file = fget(fd);
--
Gleb.