linux-kernel - [PATCH 1/2] NOMMU: There is no mlock() for NOMMU, so don't provide the bits

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Date:	Fri, 13 Mar 2009 17:33:48 +0000
From:	David Howells <dhowells@...hat.com>
To:	kosaki.motohiro@...fujitsu.com, minchan.kim@...il.com
Cc:	dhowells@...hat.com, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, peterz@...radead.org,
	nrik.Berkhan@...com, uclinux-dev@...inux.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	hannes@...xchg.org, riel@...riel.com, lee.schermerhorn@...com
Subject: [PATCH 1/2] NOMMU: There is no mlock() for NOMMU,
	so don't provide the bits

The mlock() facility does not exist for NOMMU since all mappings are
effectively locked anyway, so we don't make the bits available when they're
not useful.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 include/linux/page-flags.h |   20 +++++++++++++-------
 mm/Kconfig                 |    8 ++++++++
 mm/internal.h              |    8 +++++---
 3 files changed, 26 insertions(+), 10 deletions(-)


diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 219a523..61df177 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -96,6 +96,8 @@ enum pageflags {
 	PG_swapbacked,		/* Page is backed by RAM/swap */
 #ifdef CONFIG_UNEVICTABLE_LRU
 	PG_unevictable,		/* Page is "unevictable"  */
+#endif
+#ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 	PG_mlocked,		/* Page is vma mlocked */
 #endif
 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
@@ -234,20 +236,20 @@ PAGEFLAG_FALSE(SwapCache)
 #ifdef CONFIG_UNEVICTABLE_LRU
 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
 	TESTCLEARFLAG(Unevictable, unevictable)
+#else
+PAGEFLAG_FALSE(Unevictable) TESTCLEARFLAG_FALSE(Unevictable)
+	SETPAGEFLAG_NOOP(Unevictable) CLEARPAGEFLAG_NOOP(Unevictable)
+	__CLEARPAGEFLAG_NOOP(Unevictable)
+#endif
 
+#ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 #define MLOCK_PAGES 1
 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
 	TESTSCFLAG(Mlocked, mlocked)
-
 #else
-
 #define MLOCK_PAGES 0
 PAGEFLAG_FALSE(Mlocked)
 	SETPAGEFLAG_NOOP(Mlocked) TESTCLEARFLAG_FALSE(Mlocked)
-
-PAGEFLAG_FALSE(Unevictable) TESTCLEARFLAG_FALSE(Unevictable)
-	SETPAGEFLAG_NOOP(Unevictable) CLEARPAGEFLAG_NOOP(Unevictable)
-	__CLEARPAGEFLAG_NOOP(Unevictable)
 #endif
 
 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
@@ -367,9 +369,13 @@ static inline void __ClearPageTail(struct page *page)
 
 #ifdef CONFIG_UNEVICTABLE_LRU
 #define __PG_UNEVICTABLE	(1 << PG_unevictable)
-#define __PG_MLOCKED		(1 << PG_mlocked)
 #else
 #define __PG_UNEVICTABLE	0
+#endif
+
+#ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
+#define __PG_MLOCKED		(1 << PG_mlocked)
+#else
 #define __PG_MLOCKED		0
 #endif
 
diff --git a/mm/Kconfig b/mm/Kconfig
index a5b7781..8c89597 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -214,5 +214,13 @@ config UNEVICTABLE_LRU
 	  will use one page flag and increase the code size a little,
 	  say Y unless you know what you are doing.
 
+config HAVE_MLOCK
+	bool
+	default y if MMU=y
+
+config HAVE_MLOCKED_PAGE_BIT
+	bool
+	default y if HAVE_MLOCK=y && UNEVICTABLE_LRU=y
+
 config MMU_NOTIFIER
 	bool
diff --git a/mm/internal.h b/mm/internal.h
index 478223b..987bb03 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -63,6 +63,7 @@ static inline unsigned long page_order(struct page *page)
 	return page_private(page);
 }
 
+#ifdef CONFIG_HAVE_MLOCK
 extern long mlock_vma_pages_range(struct vm_area_struct *vma,
 			unsigned long start, unsigned long end);
 extern void munlock_vma_pages_range(struct vm_area_struct *vma,
@@ -71,6 +72,7 @@ static inline void munlock_vma_pages_all(struct vm_area_struct *vma)
 {
 	munlock_vma_pages_range(vma, vma->vm_start, vma->vm_end);
 }
+#endif
 
 #ifdef CONFIG_UNEVICTABLE_LRU
 /*
@@ -90,7 +92,7 @@ static inline void unevictable_migrate_page(struct page *new, struct page *old)
 }
 #endif
 
-#ifdef CONFIG_UNEVICTABLE_LRU
+#ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 /*
  * Called only in fault path via page_evictable() for a new page
  * to determine if it's being mapped into a LOCKED vma.
@@ -165,7 +167,7 @@ static inline void free_page_mlock(struct page *page)
 	}
 }
 
-#else /* CONFIG_UNEVICTABLE_LRU */
+#else /* CONFIG_HAVE_MLOCKED_PAGE_BIT */
 static inline int is_mlocked_vma(struct vm_area_struct *v, struct page *p)
 {
 	return 0;
@@ -175,7 +177,7 @@ static inline void mlock_vma_page(struct page *page) { }
 static inline void mlock_migrate_page(struct page *new, struct page *old) { }
 static inline void free_page_mlock(struct page *page) { }
 
-#endif /* CONFIG_UNEVICTABLE_LRU */
+#endif /* CONFIG_HAVE_MLOCKED_PAGE_BIT */
 
 /*
  * Return the mem_map entry representing the 'offset' subpage within

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