Re: [PATCH v2 2/2] mm: remove odd HAVE_PTE_SPECIAL

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On 10/04/18 16:25, Laurent Dufour wrote:
Remove the additional define HAVE_PTE_SPECIAL and rely directly on
CONFIG_ARCH_HAS_PTE_SPECIAL.

There is no functional change introduced by this patch

Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
---
  mm/memory.c | 23 ++++++++++-------------
  1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 96910c625daa..53b6344a90d2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -817,19 +817,13 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
   * PFNMAP mappings in order to support COWable mappings.
   *
   */
-#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
-# define HAVE_PTE_SPECIAL 1
-#else
-# define HAVE_PTE_SPECIAL 0
-#endif
  struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
  			     pte_t pte, bool with_public_device)
  {
  	unsigned long pfn = pte_pfn(pte);
- if (HAVE_PTE_SPECIAL) {
-		if (likely(!pte_special(pte)))
-			goto check_pfn;
+#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL

Nit: Couldn't you use IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) within the existing code structure to avoid having to add these #ifdefs?

Robin.

+	if (unlikely(pte_special(pte))) {
  		if (vma->vm_ops && vma->vm_ops->find_special_page)
  			return vma->vm_ops->find_special_page(vma, addr);
  		if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
@@ -862,7 +856,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
  		return NULL;
  	}
- /* !HAVE_PTE_SPECIAL case follows: */
+#else	/* CONFIG_ARCH_HAS_PTE_SPECIAL */
if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
  		if (vma->vm_flags & VM_MIXEDMAP) {
@@ -881,7 +875,8 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
if (is_zero_pfn(pfn))
  		return NULL;
-check_pfn:
+#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
+
  	if (unlikely(pfn > highest_memmap_pfn)) {
  		print_bad_pte(vma, addr, pte, NULL);
  		return NULL;
@@ -891,7 +886,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
  	 * NOTE! We still have PageReserved() pages in the page tables.
  	 * eg. VDSO mappings can cause them to exist.
  	 */
-out:
+out: __maybe_unused
  	return pfn_to_page(pfn);
  }
@@ -904,7 +899,7 @@ struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
  	/*
  	 * There is no pmd_special() but there may be special pmds, e.g.
  	 * in a direct-access (dax) mapping, so let's just replicate the
-	 * !HAVE_PTE_SPECIAL case from vm_normal_page() here.
+	 * !CONFIG_ARCH_HAS_PTE_SPECIAL case from vm_normal_page() here.
  	 */
  	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
  		if (vma->vm_flags & VM_MIXEDMAP) {
@@ -1926,6 +1921,7 @@ static int __vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
track_pfn_insert(vma, &pgprot, pfn); +#ifndef CONFIG_ARCH_HAS_PTE_SPECIAL
  	/*
  	 * If we don't have pte special, then we have to use the pfn_valid()
  	 * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
@@ -1933,7 +1929,7 @@ static int __vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
  	 * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP
  	 * without pte special, it would there be refcounted as a normal page.
  	 */
-	if (!HAVE_PTE_SPECIAL && !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) {
+	if (!pfn_t_devmap(pfn) && pfn_t_valid(pfn)) {
  		struct page *page;
/*
@@ -1944,6 +1940,7 @@ static int __vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
  		page = pfn_to_page(pfn_t_to_pfn(pfn));
  		return insert_page(vma, addr, page, pgprot);
  	}
+#endif
  	return insert_pfn(vma, addr, pfn, pgprot, mkwrite);
  }
--
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