[PATCH 1/3] Add flag to request pages are locked after page fault

[Eric B Munson <emunson@akamai.com>]

The cost of faulting in all memory to be locked can be very high when
working with large mappings.  If only portions of the mapping will be
used this can incur a high penalty for locking.  This patch introduces
the ability to request that pages are not pre-faulted, but are placed on
the unevictable LRU when they are finally faulted in.

To keep accounting checks out of the page fault path, users are billed
for the entire mapping lock as if MAP_LOCKED was used.

Signed-off-by: Eric B Munson <emunson@akamai.com>
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-mm@kvack.org
Cc: linux-arch@vger.kernel.org
Cc: linux-api@vger.kernel.org
---
 arch/alpha/include/uapi/asm/mman.h   | 1 +
 arch/mips/include/uapi/asm/mman.h    | 1 +
 arch/parisc/include/uapi/asm/mman.h  | 1 +
 arch/powerpc/include/uapi/asm/mman.h | 1 +
 arch/sparc/include/uapi/asm/mman.h   | 1 +
 arch/tile/include/uapi/asm/mman.h    | 1 +
 arch/xtensa/include/uapi/asm/mman.h  | 1 +
 include/linux/mm.h                   | 1 +
 include/linux/mman.h                 | 3 ++-
 include/uapi/asm-generic/mman.h      | 1 +
 mm/mmap.c                            | 4 ++--
 mm/swap.c                            | 3 ++-
 12 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch/alpha/include/uapi/asm/mman.h b/arch/alpha/include/uapi/asm/mman.h
index 0086b47..15e96e1 100644
--- a/arch/alpha/include/uapi/asm/mman.h
+++ b/arch/alpha/include/uapi/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_LOCKONFAULT	0x200000	/* Lock pages after they are faulted in, do not prefault */
 
 #define MS_ASYNC	1		/* sync memory asynchronously */
 #define MS_SYNC		2		/* synchronous memory sync */
diff --git a/arch/mips/include/uapi/asm/mman.h b/arch/mips/include/uapi/asm/mman.h
index cfcb876..47846a5 100644
--- a/arch/mips/include/uapi/asm/mman.h
+++ b/arch/mips/include/uapi/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_LOCKONFAULT	0x100000	/* Lock pages after they are faulted in, do not prefault */
 
 /*
  * Flags for msync
diff --git a/arch/parisc/include/uapi/asm/mman.h b/arch/parisc/include/uapi/asm/mman.h
index 294d251..1514cd7 100644
--- a/arch/parisc/include/uapi/asm/mman.h
+++ b/arch/parisc/include/uapi/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_LOCKONFAULT	0x100000	/* Lock pages after they are faulted in, do not prefault */
 
 #define MS_SYNC		1		/* synchronous memory sync */
 #define MS_ASYNC	2		/* sync memory asynchronously */
diff --git a/arch/powerpc/include/uapi/asm/mman.h b/arch/powerpc/include/uapi/asm/mman.h
index 6ea26df..fce74fe 100644
--- a/arch/powerpc/include/uapi/asm/mman.h
+++ b/arch/powerpc/include/uapi/asm/mman.h
@@ -27,5 +27,6 @@
 #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_LOCKONFAULT	0x80000		/* Lock pages after they are faulted in, do not prefault */
 
 #endif /* _UAPI_ASM_POWERPC_MMAN_H */
diff --git a/arch/sparc/include/uapi/asm/mman.h b/arch/sparc/include/uapi/asm/mman.h
index 0b14df3..12425d8 100644
--- a/arch/sparc/include/uapi/asm/mman.h
+++ b/arch/sparc/include/uapi/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_LOCKONFAULT	0x80000		/* Lock pages after they are faulted in, do not prefault */
 
 
 #endif /* _UAPI__SPARC_MMAN_H__ */
diff --git a/arch/tile/include/uapi/asm/mman.h b/arch/tile/include/uapi/asm/mman.h
index 81b8fc3..ec04eaf 100644
--- a/arch/tile/include/uapi/asm/mman.h
+++ b/arch/tile/include/uapi/asm/mman.h
@@ -29,6 +29,7 @@
 #define MAP_DENYWRITE	0x0800		/* ETXTBSY */
 #define MAP_EXECUTABLE	0x1000		/* mark it as an executable */
 #define MAP_HUGETLB	0x4000		/* create a huge page mapping */
+#define MAP_LOCKONFAULT	0x8000		/* Lock pages after they are faulted in, do not prefault */
 
 
 /*
diff --git a/arch/xtensa/include/uapi/asm/mman.h b/arch/xtensa/include/uapi/asm/mman.h
index 201aec0..42d43cc 100644
--- a/arch/xtensa/include/uapi/asm/mman.h
+++ b/arch/xtensa/include/uapi/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_LOCKONFAULT	0x100000	/* Lock pages after they are faulted in, do not prefault */
 #ifdef CONFIG_MMAP_ALLOW_UNINITIALIZED
 # define MAP_UNINITIALIZED 0x4000000	/* For anonymous mmap, memory could be
 					 * uninitialized */
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0755b9f..3e31457 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -126,6 +126,7 @@ extern unsigned int kobjsize(const void *objp);
 #define VM_PFNMAP	0x00000400	/* Page-ranges managed without "struct page", just pure PFN */
 #define VM_DENYWRITE	0x00000800	/* ETXTBSY on write attempts.. */
 
+#define VM_LOCKONFAULT	0x00001000	/* Lock the pages covered when they are faulted in */
 #define VM_LOCKED	0x00002000
 #define VM_IO           0x00004000	/* Memory mapped I/O or similar */
 
diff --git a/include/linux/mman.h b/include/linux/mman.h
index 16373c8..437264b 100644
--- a/include/linux/mman.h
+++ b/include/linux/mman.h
@@ -86,7 +86,8 @@ calc_vm_flag_bits(unsigned long flags)
 {
 	return _calc_vm_trans(flags, MAP_GROWSDOWN,  VM_GROWSDOWN ) |
 	       _calc_vm_trans(flags, MAP_DENYWRITE,  VM_DENYWRITE ) |
-	       _calc_vm_trans(flags, MAP_LOCKED,     VM_LOCKED    );
+	       _calc_vm_trans(flags, MAP_LOCKED,     VM_LOCKED    ) |
+	       _calc_vm_trans(flags, MAP_LOCKONFAULT,VM_LOCKONFAULT);
 }
 
 unsigned long vm_commit_limit(void);
diff --git a/include/uapi/asm-generic/mman.h b/include/uapi/asm-generic/mman.h
index e9fe6fd..fc4e586 100644
--- a/include/uapi/asm-generic/mman.h
+++ b/include/uapi/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_LOCKONFAULT	0x80000		/* Lock pages after they are faulted in, do not prefault */
 
 /* Bits [26:31] are reserved, see mman-common.h for MAP_HUGETLB usage */
 
diff --git a/mm/mmap.c b/mm/mmap.c
index bb50cac..ba1a6bf 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1233,7 +1233,7 @@ static inline int mlock_future_check(struct mm_struct *mm,
 	unsigned long locked, lock_limit;
 
 	/*  mlock MCL_FUTURE? */
-	if (flags & VM_LOCKED) {
+	if (flags & (VM_LOCKED | VM_LOCKONFAULT)) {
 		locked = len >> PAGE_SHIFT;
 		locked += mm->locked_vm;
 		lock_limit = rlimit(RLIMIT_MEMLOCK);
@@ -1301,7 +1301,7 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
 	vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
 			mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
 
-	if (flags & MAP_LOCKED)
+	if (flags & (MAP_LOCKED | MAP_LOCKONFAULT))
 		if (!can_do_mlock())
 			return -EPERM;
 
diff --git a/mm/swap.c b/mm/swap.c
index a7251a8..07c905e 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -711,7 +711,8 @@ void lru_cache_add_active_or_unevictable(struct page *page,
 {
 	VM_BUG_ON_PAGE(PageLRU(page), page);
 
-	if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED)) {
+	if (likely((vma->vm_flags & (VM_LOCKED | VM_LOCKONFAULT)) == 0) ||
+		   (vma->vm_flags & VM_SPECIAL)) {
 		SetPageActive(page);
 		lru_cache_add(page);
 		return;
-- 
1.9.1