Re: [PATCH 13 of 66] export maybe_mkwrite

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Andrea Arcangeli wrote:
From: Andrea Arcangeli <aarcange@xxxxxxxxxx>

huge_memory.c needs it too when it fallbacks in copying hugepages into regular
fragmented pages if hugepage allocation fails during COW.

Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Acked-by: Mel Gorman <mel@xxxxxxxxx>

It wasn't good idea to do it. mm/memory.c is used only for system with MMU. System without MMU are broken.

Not sure what the right fix is but anyway I think use one ifdef make sense (git patch in attachment).

Regards,
Michal


diff --git a/include/linux/mm.h b/include/linux/mm.h
index 956a355..f6385fc 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -470,6 +470,7 @@ static inline void set_compound_order(struct page *page, unsigned long order)
 	page[1].lru.prev = (void *)order;
 }

+#ifdef CONFIG_MMU
 /*
  * Do pte_mkwrite, but only if the vma says VM_WRITE.  We do this when
  * servicing faults for write access.  In the normal case, do always want
@@ -482,6 +483,7 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
 		pte = pte_mkwrite(pte);
 	return pte;
 }
+#endif

 /*
  * Multiple processes may "see" the same page. E.g. for untouched


---

diff --git a/include/linux/mm.h b/include/linux/mm.h
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -416,6 +416,19 @@ static inline void set_compound_order(st
 }
/*
+ * Do pte_mkwrite, but only if the vma says VM_WRITE.  We do this when
+ * servicing faults for write access.  In the normal case, do always want
+ * pte_mkwrite.  But get_user_pages can cause write faults for mappings
+ * that do not have writing enabled, when used by access_process_vm.
+ */
+static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
+{
+	if (likely(vma->vm_flags & VM_WRITE))
+		pte = pte_mkwrite(pte);
+	return pte;
+}
+
+/*
  * Multiple processes may "see" the same page. E.g. for untouched
  * mappings of /dev/null, all processes see the same page full of
  * zeroes, and text pages of executables and shared libraries have
diff --git a/mm/memory.c b/mm/memory.c
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2048,19 +2048,6 @@ static inline int pte_unmap_same(struct return same;
 }
-/*
- * Do pte_mkwrite, but only if the vma says VM_WRITE.  We do this when
- * servicing faults for write access.  In the normal case, do always want
- * pte_mkwrite.  But get_user_pages can cause write faults for mappings
- * that do not have writing enabled, when used by access_process_vm.
- */
-static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
-{
-	if (likely(vma->vm_flags & VM_WRITE))
-		pte = pte_mkwrite(pte);
-	return pte;
-}
-
 static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
 {
 	/*
--
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--
Michal Simek, Ing. (M.Eng)
PetaLogix - Linux Solutions for a Reconfigurable World
w: www.petalogix.com p: +61-7-30090663,+42-0-721842854 f: +61-7-30090663
>From 9d09534daec636eafed279352c6b34d3b47c3a09 Mon Sep 17 00:00:00 2001
From: Michal Simek <monstr@xxxxxxxxx>
Date: Mon, 17 Jan 2011 15:09:36 +0100
Subject: [PATCH] mm: System without MMU do not need pte_mkwrite

The patch "thp: export maybe_mkwrite"
(sha1 14fd403f2146f740942d78af4e0ee59396ad8eab)
break systems without MMU.

Signed-off-by: Michal Simek <monstr@xxxxxxxxx>
---
 include/linux/mm.h |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 956a355..f6385fc 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -470,6 +470,7 @@ static inline void set_compound_order(struct page *page, unsigned long order)
 	page[1].lru.prev = (void *)order;
 }
 
+#ifdef CONFIG_MMU
 /*
  * Do pte_mkwrite, but only if the vma says VM_WRITE.  We do this when
  * servicing faults for write access.  In the normal case, do always want
@@ -482,6 +483,7 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
 		pte = pte_mkwrite(pte);
 	return pte;
 }
+#endif
 
 /*
  * Multiple processes may "see" the same page. E.g. for untouched
-- 
1.5.5.6


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