Re: [PATCH 1/2] Export get_user_pages_fast

[Nick Piggin]

On Thursday 31 July 2008 17:02, Andrew Morton wrote:
> On Thu, 31 Jul 2008 09:43:59 +0300 Avi Kivity <avi@xxxxxxxxxxxx> wrote:

> > Surprised.  Why not an out-of-line function?  Would eliminate the
> > present discussion as well.
>
> Excellent question!

Like this?
Index: linux-2.6/include/linux/mm.h
===================================================================
--- linux-2.6.orig/include/linux/mm.h	2008-07-31 17:59:04.000000000 +1000
+++ linux-2.6/include/linux/mm.h	2008-07-31 18:01:51.000000000 +1000
@@ -834,7 +834,6 @@ extern int mprotect_fixup(struct vm_area
 			  struct vm_area_struct **pprev, unsigned long start,
 			  unsigned long end, unsigned long newflags);
 
-#ifdef CONFIG_HAVE_GET_USER_PAGES_FAST
 /*
  * get_user_pages_fast provides equivalent functionality to get_user_pages,
  * operating on current and current->mm (force=0 and doesn't return any vmas).
@@ -848,25 +847,6 @@ extern int mprotect_fixup(struct vm_area
 int get_user_pages_fast(unsigned long start, int nr_pages, int write,
 			struct page **pages);
 
-#else
-/*
- * Should probably be moved to asm-generic, and architectures can include it if
- * they don't implement their own get_user_pages_fast.
- */
-#define get_user_pages_fast(start, nr_pages, write, pages)	\
-({								\
-	struct mm_struct *mm = current->mm;			\
-	int ret;						\
-								\
-	down_read(&mm->mmap_sem);				\
-	ret = get_user_pages(current, mm, start, nr_pages,	\
-					write, 0, pages, NULL);	\
-	up_read(&mm->mmap_sem);					\
-								\
-	ret;							\
-})
-#endif
-
 /*
  * A callback you can register to apply pressure to ageable caches.
  *
Index: linux-2.6/mm/memory.c
===================================================================
--- linux-2.6.orig/mm/memory.c	2008-07-31 17:59:26.000000000 +1000
+++ linux-2.6/mm/memory.c	2008-07-31 18:01:25.000000000 +1000
@@ -1270,6 +1270,21 @@ int get_user_pages(struct task_struct *t
 }
 EXPORT_SYMBOL(get_user_pages);
 
+int __attribute__((weak)) get_user_pages_fast(unsigned long start,
+				int nr_pages, int write, struct page **pages)
+{
+	struct mm_struct *mm = current->mm;
+	int ret;
+
+	down_read(&mm->mmap_sem);
+	ret = get_user_pages(current, mm, start, nr_pages,
+					write, 0, pages, NULL);
+	up_read(&mm->mmap_sem);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(get_user_pages_fast);
+
 pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
 			spinlock_t **ptl)
 {
Index: linux-2.6/arch/x86/Kconfig
===================================================================
--- linux-2.6.orig/arch/x86/Kconfig	2008-07-31 18:08:35.000000000 +1000
+++ linux-2.6/arch/x86/Kconfig	2008-07-31 18:08:53.000000000 +1000
@@ -22,7 +22,6 @@ config X86
 	select HAVE_IDE
 	select HAVE_OPROFILE
 	select HAVE_IOREMAP_PROT
-	select HAVE_GET_USER_PAGES_FAST
 	select HAVE_KPROBES
 	select ARCH_WANT_OPTIONAL_GPIOLIB
 	select HAVE_KRETPROBES
Index: linux-2.6/arch/x86/mm/Makefile
===================================================================
--- linux-2.6.orig/arch/x86/mm/Makefile	2008-07-31 18:08:58.000000000 +1000
+++ linux-2.6/arch/x86/mm/Makefile	2008-07-31 18:09:07.000000000 +1000
@@ -1,7 +1,6 @@
 obj-y	:=  init_$(BITS).o fault.o ioremap.o extable.o pageattr.o mmap.o \
-	    pat.o pgtable.o
+	    pat.o pgtable.o gup.o
 
-obj-$(CONFIG_HAVE_GET_USER_PAGES_FAST) += gup.o
 obj-$(CONFIG_X86_32)		+= pgtable_32.o
 
 obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o