[-mm][splitlru][PATCH 0/3] munlock rework

[-mm][splitlru][PATCH 0/3] munlock rework

[kosaki.motohiro]

-- 

old munlock processing of unevictable-lru use pagewalk.
because get_user_pages() can't grab PROT_NONE page.

then, current -mm has two problem.
  - build error on nommu machine
  - runtime error on HIGHPTE machine.

So, I hope rework below concept

	Old implementation
	   - use pagewalk

	New implementation
	   - use __get_user_pages()


I tested this patch on
  IA64:                 >24H stress workload
  x86_64:               ditto
  x86_32 with HIGHPTE:  only half hour



Li-san, Could you please try to this patch on your 32bit machine?

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[-mm][splitlru][PATCH 1/3] introduce __get_user_pages()

[kosaki.motohiro]

[-- Attachment #1: __get_user_pages.patch --]
[-- Type: text/plain, Size: 3336 bytes --]

new munlock processing need to GUP_FLAGS_IGNORE_VMA_PERMISSIONS.
because current get_user_pages() can't grab PROT_NONE pages theresore
it cause PROT_NONE pages can't munlock.



Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Li Zefan <lizf@cn.fujitsu.com>
CC: Hugh Dickins <hugh@veritas.com>
CC: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
CC: Rik van Riel <riel@redhat.com>

---
 mm/internal.h |    8 ++++++++
 mm/memory.c   |   37 +++++++++++++++++++++++++++++++------
 2 files changed, 39 insertions(+), 6 deletions(-)

Index: b/mm/memory.c
===================================================================
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1108,12 +1108,17 @@ static inline int use_zero_page(struct v
 	return !vma->vm_ops || !vma->vm_ops->fault;
 }
 
-int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
-		unsigned long start, int len, int write, int force,
+
+
+int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
+		     unsigned long start, int len, int flags,
 		struct page **pages, struct vm_area_struct **vmas)
 {
 	int i;
-	unsigned int vm_flags;
+	unsigned int vm_flags = 0;
+	int write = !!(flags & GUP_FLAGS_WRITE);
+	int force = !!(flags & GUP_FLAGS_FORCE);
+	int ignore = !!(flags & GUP_FLAGS_IGNORE_VMA_PERMISSIONS);
 
 	if (len <= 0)
 		return 0;
@@ -1137,7 +1142,9 @@ int get_user_pages(struct task_struct *t
 			pud_t *pud;
 			pmd_t *pmd;
 			pte_t *pte;
-			if (write) /* user gate pages are read-only */
+
+			/* user gate pages are read-only */
+			if (!ignore && write)
 				return i ? : -EFAULT;
 			if (pg > TASK_SIZE)
 				pgd = pgd_offset_k(pg);
@@ -1169,8 +1176,9 @@ int get_user_pages(struct task_struct *t
 			continue;
 		}
 
-		if (!vma || (vma->vm_flags & (VM_IO | VM_PFNMAP))
-				|| !(vm_flags & vma->vm_flags))
+		if (!vma ||
+		    (vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
+		    (!ignore && !(vm_flags & vma->vm_flags)))
 			return i ? : -EFAULT;
 
 		if (is_vm_hugetlb_page(vma)) {
@@ -1245,6 +1253,23 @@ int get_user_pages(struct task_struct *t
 	} while (len);
 	return i;
 }
+
+int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
+		unsigned long start, int len, int write, int force,
+		struct page **pages, struct vm_area_struct **vmas)
+{
+	int flags = 0;
+
+	if (write)
+		flags |= GUP_FLAGS_WRITE;
+	if (force)
+		flags |= GUP_FLAGS_FORCE;
+
+	return __get_user_pages(tsk, mm,
+				start, len, flags,
+				pages, vmas);
+}
+
 EXPORT_SYMBOL(get_user_pages);
 
 pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
Index: b/mm/internal.h
===================================================================
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -243,4 +243,12 @@ static inline void mminit_validate_memmo
 }
 #endif /* CONFIG_SPARSEMEM */
 
+#define GUP_FLAGS_WRITE                  0x1
+#define GUP_FLAGS_FORCE                  0x2
+#define GUP_FLAGS_IGNORE_VMA_PERMISSIONS 0x4
+
+int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
+		     unsigned long start, int len, int flags,
+		     struct page **pages, struct vm_area_struct **vmas);
+
 #endif

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Re: [-mm][splitlru][PATCH 1/3] introduce __get_user_pages()

[KOSAKI Motohiro]

> new munlock processing need to GUP_FLAGS_IGNORE_VMA_PERMISSIONS.
> because current get_user_pages() can't grab PROT_NONE pages theresore
> it cause PROT_NONE pages can't munlock.
> 
> 
> 
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> CC: Li Zefan <lizf@cn.fujitsu.com>
> CC: Hugh Dickins <hugh@veritas.com>
> CC: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
> CC: Rik van Riel <riel@redhat.com>


sorry, I forgot to change nommu.c
below patch is new version.

Unfortunately, I don't have nommu machine.
Then I beat up nommu tester...



---
 mm/internal.h |    8 ++++++++
 mm/memory.c   |   37 +++++++++++++++++++++++++++++++------
 mm/nommu.c    |   42 +++++++++++++++++++++++++++++++-----------
 3 files changed, 70 insertions(+), 17 deletions(-)

Index: b/mm/memory.c
===================================================================
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1108,12 +1108,17 @@ static inline int use_zero_page(struct v
 	return !vma->vm_ops || !vma->vm_ops->fault;
 }
 
-int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
-		unsigned long start, int len, int write, int force,
+
+
+int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
+		     unsigned long start, int len, int flags,
 		struct page **pages, struct vm_area_struct **vmas)
 {
 	int i;
-	unsigned int vm_flags;
+	unsigned int vm_flags = 0;
+	int write = !!(flags & GUP_FLAGS_WRITE);
+	int force = !!(flags & GUP_FLAGS_FORCE);
+	int ignore = !!(flags & GUP_FLAGS_IGNORE_VMA_PERMISSIONS);
 
 	if (len <= 0)
 		return 0;
@@ -1137,7 +1142,9 @@ int get_user_pages(struct task_struct *t
 			pud_t *pud;
 			pmd_t *pmd;
 			pte_t *pte;
-			if (write) /* user gate pages are read-only */
+
+			/* user gate pages are read-only */
+			if (!ignore && write)
 				return i ? : -EFAULT;
 			if (pg > TASK_SIZE)
 				pgd = pgd_offset_k(pg);
@@ -1169,8 +1176,9 @@ int get_user_pages(struct task_struct *t
 			continue;
 		}
 
-		if (!vma || (vma->vm_flags & (VM_IO | VM_PFNMAP))
-				|| !(vm_flags & vma->vm_flags))
+		if (!vma ||
+		    (vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
+		    (!ignore && !(vm_flags & vma->vm_flags)))
 			return i ? : -EFAULT;
 
 		if (is_vm_hugetlb_page(vma)) {
@@ -1245,6 +1253,23 @@ int get_user_pages(struct task_struct *t
 	} while (len);
 	return i;
 }
+
+int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
+		unsigned long start, int len, int write, int force,
+		struct page **pages, struct vm_area_struct **vmas)
+{
+	int flags = 0;
+
+	if (write)
+		flags |= GUP_FLAGS_WRITE;
+	if (force)
+		flags |= GUP_FLAGS_FORCE;
+
+	return __get_user_pages(tsk, mm,
+				start, len, flags,
+				pages, vmas);
+}
+
 EXPORT_SYMBOL(get_user_pages);
 
 pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
Index: b/mm/internal.h
===================================================================
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -243,4 +243,12 @@ static inline void mminit_validate_memmo
 }
 #endif /* CONFIG_SPARSEMEM */
 
+#define GUP_FLAGS_WRITE                  0x1
+#define GUP_FLAGS_FORCE                  0x2
+#define GUP_FLAGS_IGNORE_VMA_PERMISSIONS 0x4
+
+int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
+		     unsigned long start, int len, int flags,
+		     struct page **pages, struct vm_area_struct **vmas);
+
 #endif
Index: b/mm/nommu.c
===================================================================
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -128,20 +128,16 @@ unsigned int kobjsize(const void *objp)
 	return PAGE_SIZE << compound_order(page);
 }
 
-/*
- * get a list of pages in an address range belonging to the specified process
- * and indicate the VMA that covers each page
- * - this is potentially dodgy as we may end incrementing the page count of a
- *   slab page or a secondary page from a compound page
- * - don't permit access to VMAs that don't support it, such as I/O mappings
- */
-int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
-	unsigned long start, int len, int write, int force,
-	struct page **pages, struct vm_area_struct **vmas)
+int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
+		     unsigned long start, int len, int flags,
+		struct page **pages, struct vm_area_struct **vmas)
 {
 	struct vm_area_struct *vma;
 	unsigned long vm_flags;
 	int i;
+	int write = !!(flags & GUP_FLAGS_WRITE);
+	int force = !!(flags & GUP_FLAGS_FORCE);
+	int ignore = !!(flags & GUP_FLAGS_IGNORE_VMA_PERMISSIONS);
 
 	/* calculate required read or write permissions.
 	 * - if 'force' is set, we only require the "MAY" flags.
@@ -156,7 +152,7 @@ int get_user_pages(struct task_struct *t
 
 		/* protect what we can, including chardevs */
 		if (vma->vm_flags & (VM_IO | VM_PFNMAP) ||
-		    !(vm_flags & vma->vm_flags))
+		    (!ignore && !(vm_flags & vma->vm_flags)))
 			goto finish_or_fault;
 
 		if (pages) {
@@ -174,6 +170,30 @@ int get_user_pages(struct task_struct *t
 finish_or_fault:
 	return i ? : -EFAULT;
 }
+
+
+/*
+ * get a list of pages in an address range belonging to the specified process
+ * and indicate the VMA that covers each page
+ * - this is potentially dodgy as we may end incrementing the page count of a
+ *   slab page or a secondary page from a compound page
+ * - don't permit access to VMAs that don't support it, such as I/O mappings
+ */
+int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
+	unsigned long start, int len, int write, int force,
+	struct page **pages, struct vm_area_struct **vmas)
+{
+	int flags = 0;
+
+	if (write)
+		flags |= GUP_FLAGS_WRITE;
+	if (force)
+		flags |= GUP_FLAGS_FORCE;
+
+	return __get_user_pages(tsk, mm,
+				start, len, flags,
+				pages, vmas);
+}
 EXPORT_SYMBOL(get_user_pages);
 
 DEFINE_RWLOCK(vmlist_lock);



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[-mm][splitlru][PATCH 2/3] split LRU: munlock rework

[kosaki.motohiro]

[-- Attachment #1: munlock-rework.patch --]
[-- Type: text/plain, Size: 7004 bytes --]

current munlock processing use to pagewalk.
its cause two problems.
  - build error on nommu machine
  - runtime error on HIGHPTE machine.

This patch fixes it.



Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Li Zefan <lizf@cn.fujitsu.com>
CC: Hugh Dickins <hugh@veritas.com>
CC: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
CC: Rik van Riel <riel@redhat.com>

---
 mm/mlock.c |  152 ++++++++++++++-----------------------------------------------
 1 file changed, 35 insertions(+), 117 deletions(-)

Index: b/mm/mlock.c
===================================================================
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -147,18 +147,33 @@ static void munlock_vma_page(struct page
  * vma->vm_mm->mmap_sem must be held for write.
  */
 static int __mlock_vma_pages_range(struct vm_area_struct *vma,
-			unsigned long start, unsigned long end)
+				   unsigned long start, unsigned long end,
+				   int mlock)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	unsigned long addr = start;
 	struct page *pages[16]; /* 16 gives a reasonable batch */
-	int write = !!(vma->vm_flags & VM_WRITE);
 	int nr_pages = (end - start) / PAGE_SIZE;
 	int ret;
+	int gup_flags = 0;
+
+	VM_BUG_ON(start & ~PAGE_MASK);
+	VM_BUG_ON(end   & ~PAGE_MASK);
+	VM_BUG_ON(start < vma->vm_start);
+	VM_BUG_ON(end   > vma->vm_end);
+	VM_BUG_ON((!rwsem_is_locked(&mm->mmap_sem)) &&
+		  (atomic_read(&mm->mm_users) != 0));
+
+	/*
+	 * mlock:   don't page populate if page has PROT_NONE permission.
+	 * munlock: the pages always do munlock althrough
+	 *          its has PROT_NONE permission.
+	 */
+	if (!mlock)
+		gup_flags |= GUP_FLAGS_IGNORE_VMA_PERMISSIONS;
 
-	VM_BUG_ON(start & ~PAGE_MASK || end & ~PAGE_MASK);
-	VM_BUG_ON(start < vma->vm_start || end > vma->vm_end);
-	VM_BUG_ON(!rwsem_is_locked(&vma->vm_mm->mmap_sem));
+	if (vma->vm_flags & VM_WRITE)
+		gup_flags |= GUP_FLAGS_WRITE;
 
 	lru_add_drain_all();	/* push cached pages to LRU */
 
@@ -171,9 +186,9 @@ static int __mlock_vma_pages_range(struc
 		 * get_user_pages makes pages present if we are
 		 * setting mlock.
 		 */
-		ret = get_user_pages(current, mm, addr,
+		ret = __get_user_pages(current, mm, addr,
 				min_t(int, nr_pages, ARRAY_SIZE(pages)),
-				write, 0, pages, NULL);
+				gup_flags, pages, NULL);
 		/*
 		 * This can happen for, e.g., VM_NONLINEAR regions before
 		 * a page has been allocated and mapped at a given offset,
@@ -202,8 +217,12 @@ static int __mlock_vma_pages_range(struc
 			 * us.  Check after acquiring page lock.
 			 */
 			lock_page(page);
-			if (page->mapping)
-				mlock_vma_page(page);
+			if (page->mapping) {
+				if (mlock)
+					mlock_vma_page(page);
+				else
+					munlock_vma_page(page);
+			}
 			unlock_page(page);
 			put_page(page);		/* ref from get_user_pages() */
 
@@ -221,120 +240,19 @@ static int __mlock_vma_pages_range(struc
 	return 0;	/* count entire vma as locked_vm */
 }
 
-/*
- * private structure for munlock page table walk
- */
-struct munlock_page_walk {
-	struct vm_area_struct *vma;
-	pmd_t                 *pmd; /* for migration_entry_wait() */
-};
-
-/*
- * munlock normal pages for present ptes
- */
-static int __munlock_pte_handler(pte_t *ptep, unsigned long addr,
-				   unsigned long end, struct mm_walk *walk)
-{
-	struct munlock_page_walk *mpw = walk->private;
-	swp_entry_t entry;
-	struct page *page;
-	pte_t pte;
-
-retry:
-	pte = *ptep;
-	/*
-	 * If it's a swap pte, we might be racing with page migration.
-	 */
-	if (unlikely(!pte_present(pte))) {
-		if (!is_swap_pte(pte))
-			goto out;
-		entry = pte_to_swp_entry(pte);
-		if (is_migration_entry(entry)) {
-			migration_entry_wait(mpw->vma->vm_mm, mpw->pmd, addr);
-			goto retry;
-		}
-		goto out;
-	}
-
-	page = vm_normal_page(mpw->vma, addr, pte);
-	if (!page)
-		goto out;
-
-	lock_page(page);
-	if (!page->mapping) {
-		unlock_page(page);
-		goto retry;
-	}
-	munlock_vma_page(page);
-	unlock_page(page);
-
-out:
-	return 0;
-}
-
-/*
- * Save pmd for pte handler for waiting on migration entries
- */
-static int __munlock_pmd_handler(pmd_t *pmd, unsigned long addr,
-				 unsigned long end, struct mm_walk *walk)
-{
-	struct munlock_page_walk *mpw = walk->private;
-
-	mpw->pmd = pmd;
-	return 0;
-}
-
-
-/*
- * munlock a range of pages in the vma using standard page table walk.
- *
- * vma->vm_mm->mmap_sem must be held for write.
- */
-static void __munlock_vma_pages_range(struct vm_area_struct *vma,
-			      unsigned long start, unsigned long end)
-{
-	struct mm_struct *mm = vma->vm_mm;
-	struct munlock_page_walk mpw = {
-		.vma = vma,
-	};
-	struct mm_walk munlock_page_walk = {
-		.pmd_entry = __munlock_pmd_handler,
-		.pte_entry = __munlock_pte_handler,
-		.private = &mpw,
-		.mm = mm,
-	};
-
-	VM_BUG_ON(start & ~PAGE_MASK || end & ~PAGE_MASK);
-	VM_BUG_ON((!rwsem_is_locked(&mm->mmap_sem)) &&
-		  (atomic_read(&mm->mm_users) != 0));
-	VM_BUG_ON(start < vma->vm_start);
-	VM_BUG_ON(end > vma->vm_end);
-
-	lru_add_drain_all();	/* push cached pages to LRU */
-	walk_page_range(start, end, &munlock_page_walk);
-	lru_add_drain_all();	/* to update stats */
-}
-
 #else /* CONFIG_UNEVICTABLE_LRU */
 
 /*
  * Just make pages present if VM_LOCKED.  No-op if unlocking.
  */
 static int __mlock_vma_pages_range(struct vm_area_struct *vma,
-			unsigned long start, unsigned long end)
+				   unsigned long start, unsigned long end,
+				   int mlock)
 {
-	if (vma->vm_flags & VM_LOCKED)
+	if (mlock && (vma->vm_flags & VM_LOCKED))
 		make_pages_present(start, end);
 	return 0;
 }
-
-/*
- * munlock a range of pages in the vma -- no-op.
- */
-static void __munlock_vma_pages_range(struct vm_area_struct *vma,
-			      unsigned long start, unsigned long end)
-{
-}
 #endif /* CONFIG_UNEVICTABLE_LRU */
 
 /*
@@ -357,7 +275,7 @@ int mlock_vma_pages_range(struct vm_area
 			is_vm_hugetlb_page(vma) ||
 			vma == get_gate_vma(current))) {
 		downgrade_write(&mm->mmap_sem);
-		nr_pages = __mlock_vma_pages_range(vma, start, end);
+		nr_pages = __mlock_vma_pages_range(vma, start, end, 1);
 
 		up_read(&mm->mmap_sem);
 		/* vma can change or disappear */
@@ -392,7 +310,7 @@ void munlock_vma_pages_range(struct vm_a
 			   unsigned long start, unsigned long end)
 {
 	vma->vm_flags &= ~VM_LOCKED;
-	__munlock_vma_pages_range(vma, start, end);
+	__mlock_vma_pages_range(vma, start, end, 0);
 }
 
 /*
@@ -469,7 +387,7 @@ success:
 		 */
 		downgrade_write(&mm->mmap_sem);
 
-		ret = __mlock_vma_pages_range(vma, start, end);
+		ret = __mlock_vma_pages_range(vma, start, end, 1);
 		if (ret > 0) {
 			mm->locked_vm -= ret;
 			ret = 0;
@@ -495,7 +413,7 @@ success:
 		 * while.  Should we downgrade the semaphore for both lock
 		 * AND unlock ?
 		 */
-		__munlock_vma_pages_range(vma, start, end);
+		__mlock_vma_pages_range(vma, start, end, 0);
 	}
 
 out:

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Re: [-mm][splitlru][PATCH 2/3] split LRU: munlock rework

[Rik van Riel]

On Sat, 19 Jul 2008 17:42:15 +0900
kosaki.motohiro@jp.fujitsu.com wrote:

> current munlock processing use to pagewalk.
> its cause two problems.
>   - build error on nommu machine
>   - runtime error on HIGHPTE machine.
> 
> This patch fixes it.
> 
> 
> 
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

Acked-by: Rik van Riel <riel@redhat.com>

-- 
All rights reversed.

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[-mm][splitlru][PATCH 3/3] revert to unevictable-lru-infrastructure-kconfig-fix.patch

[kosaki.motohiro]

[-- Attachment #1: revert-kconfig.patch --]
[-- Type: text/plain, Size: 2187 bytes --]

CONFIG_UNEVICTABLE_LRU automatically turn on CONFIG_PAGE_WALKER.
it cause build error on nommu machine.

Now, it is unnecessary because munlock was rewritten.


Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Li Zefan <lizf@cn.fujitsu.com>
CC: Hugh Dickins <hugh@veritas.com>
CC: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
CC: Rik van Riel <riel@redhat.com>

---
 init/Kconfig |    1 -
 mm/Kconfig   |    5 -----
 mm/Makefile  |    2 +-
 3 files changed, 1 insertion(+), 7 deletions(-)

Index: b/init/Kconfig
===================================================================
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -803,7 +803,6 @@ source "arch/Kconfig"
 config PROC_PAGE_MONITOR
  	default y
 	depends on PROC_FS && MMU
-	select PAGE_WALKER
 	bool "Enable /proc page monitoring" if EMBEDDED
  	help
 	  Various /proc files exist to monitor process memory utilization:
Index: b/mm/Kconfig
===================================================================
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -209,14 +209,9 @@ config VIRT_TO_BUS
 	def_bool y
 	depends on !ARCH_NO_VIRT_TO_BUS
 
-# automatically selected by UNEVICTABLE_LRU or PROC_PAGE_MONITOR
-config PAGE_WALKER
-	def_bool n
-
 config UNEVICTABLE_LRU
 	bool "Add LRU list to track non-evictable pages"
 	default y
-	select PAGE_WALKER
 	help
 	  Keeps unevictable pages off of the active and inactive pageout
 	  lists, so kswapd will not waste CPU time or have its balancing
Index: b/mm/Makefile
===================================================================
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -13,7 +13,7 @@ obj-y			:= bootmem.o filemap.o mempool.o
 			   prio_tree.o util.o mmzone.o vmstat.o backing-dev.o \
 			   page_isolation.o $(mmu-y)
 
-obj-$(CONFIG_PAGE_WALKER) += pagewalk.o
+obj-$(CONFIG_PROC_PAGE_MONITOR) += pagewalk.o
 obj-$(CONFIG_BOUNCE)	+= bounce.o
 obj-$(CONFIG_SWAP)	+= page_io.o swap_state.o swapfile.o thrash.o
 obj-$(CONFIG_HAS_DMA)	+= dmapool.o

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Re: [-mm][splitlru][PATCH 3/3] revert to unevictable-lru-infrastructure-kconfig-fix.patch

[Rik van Riel]

On Sat, 19 Jul 2008 17:42:16 +0900
kosaki.motohiro@jp.fujitsu.com wrote:

> CONFIG_UNEVICTABLE_LRU automatically turn on CONFIG_PAGE_WALKER.
> it cause build error on nommu machine.
> 
> Now, it is unnecessary because munlock was rewritten.
> 
> 
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

Acked-by: Rik van Riel <riel@redhat.com>

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All rights reversed.

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Re: [-mm][splitlru][PATCH 0/3] munlock rework

[Li Zefan]

kosaki.motohiro@jp.fujitsu.com D'uA:
> old munlock processing of unevictable-lru use pagewalk.
> because get_user_pages() can't grab PROT_NONE page.
> 
> then, current -mm has two problem.
>   - build error on nommu machine
>   - runtime error on HIGHPTE machine.
> 
> So, I hope rework below concept
> 
> 	Old implementation
> 	   - use pagewalk
> 
> 	New implementation
> 	   - use __get_user_pages()
> 
> 
> I tested this patch on
>   IA64:                 >24H stress workload
>   x86_64:               ditto
>   x86_32 with HIGHPTE:  only half hour
> 
> 
> 
> Li-san, Could you please try to this patch on your 32bit machine?

I've tested this patchset, the bug disappeared and it survived the
ltp tests :) .

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