mm, hugetlbfs: Allow an arch to always use generic versions of get_unmapped_area functions

Unlike most architectures, powerpc can only define at runtime
if it is going to use the generic arch_get_unmapped_area() or not.

Today, powerpc has a copy of the generic arch_get_unmapped_area()
because when selection HAVE_ARCH_UNMAPPED_AREA the generic
arch_get_unmapped_area() is not available.

Rename it generic_get_unmapped_area() and make it independent of
HAVE_ARCH_UNMAPPED_AREA.

Do the same for arch_get_unmapped_area_topdown() versus
HAVE_ARCH_UNMAPPED_AREA_TOPDOWN.

Do the same for hugetlb_get_unmapped_area() versus
HAVE_ARCH_HUGETLB_UNMAPPED_AREA.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/77f9d3e592f1c8511df9381aa1c4e754651da4d1.1649523076.git.christophe.leroy@csgroup.eu

fs/hugetlbfs/inode.c

@@ -195,7 +195,6 @@ out:
  * Called under mmap_write_lock(mm).
  */
 
-#ifndef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
 static unsigned long
 hugetlb_get_unmapped_area_bottomup(struct file *file, unsigned long addr,
 		unsigned long len, unsigned long pgoff, unsigned long flags)
@@ -244,9 +243,10 @@ hugetlb_get_unmapped_area_topdown(struct file *file, unsigned long addr,
 	return addr;
 }
 
-static unsigned long
-hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
-		unsigned long len, unsigned long pgoff, unsigned long flags)
+unsigned long
+generic_hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+				  unsigned long len, unsigned long pgoff,
+				  unsigned long flags)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
@@ -283,6 +283,15 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 	return hugetlb_get_unmapped_area_bottomup(file, addr, len,
 			pgoff, flags);
 }
+
+#ifndef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
+static unsigned long
+hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+			  unsigned long len, unsigned long pgoff,
+			  unsigned long flags)
+{
+	return generic_hugetlb_get_unmapped_area(file, addr, len, pgoff, flags);
+}
 #endif
 
 static size_t

include/linux/hugetlb.h

@@ -519,6 +519,11 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 					unsigned long flags);
 #endif /* HAVE_ARCH_HUGETLB_UNMAPPED_AREA */
 
+unsigned long
+generic_hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+				  unsigned long len, unsigned long pgoff,
+				  unsigned long flags);
+
 /*
  * huegtlb page specific state flags.  These flags are located in page.private
  * of the hugetlb head page.  Functions created via the below macros should be

include/linux/sched/mm.h

@@ -153,6 +153,15 @@ extern unsigned long
 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
 			  unsigned long len, unsigned long pgoff,
 			  unsigned long flags);
+
+unsigned long
+generic_get_unmapped_area(struct file *filp, unsigned long addr,
+			  unsigned long len, unsigned long pgoff,
+			  unsigned long flags);
+unsigned long
+generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
+				  unsigned long len, unsigned long pgoff,
+				  unsigned long flags);
 #else
 static inline void arch_pick_mmap_layout(struct mm_struct *mm,
 					 struct rlimit *rlim_stack) {}

mm/mmap.c

@@ -2128,10 +2128,10 @@ unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info)
  *
  * This function "knows" that -ENOMEM has the bits set.
  */
-#ifndef HAVE_ARCH_UNMAPPED_AREA
 unsigned long
-arch_get_unmapped_area(struct file *filp, unsigned long addr,
-		unsigned long len, unsigned long pgoff, unsigned long flags)
+generic_get_unmapped_area(struct file *filp, unsigned long addr,
+			  unsigned long len, unsigned long pgoff,
+			  unsigned long flags)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma, *prev;
@@ -2161,15 +2161,23 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
 	info.align_offset = 0;
 	return vm_unmapped_area(&info);
 }
+
+#ifndef HAVE_ARCH_UNMAPPED_AREA
+unsigned long
+arch_get_unmapped_area(struct file *filp, unsigned long addr,
+		       unsigned long len, unsigned long pgoff,
+		       unsigned long flags)
+{
+	return generic_get_unmapped_area(filp, addr, len, pgoff, flags);
+}
 #endif
 
 /*
  * This mmap-allocator allocates new areas top-down from below the
  * stack's low limit (the base):
  */
-#ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
 unsigned long
-arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
+generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
 				  unsigned long len, unsigned long pgoff,
 				  unsigned long flags)
 {
@@ -2219,6 +2227,15 @@ arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
 
 	return addr;
 }
+
+#ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
+unsigned long
+arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
+			       unsigned long len, unsigned long pgoff,
+			       unsigned long flags)
+{
+	return generic_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
+}
 #endif
 
 unsigned long