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

[Laurent Dufour]

On 10/04/2018 17:58, Robin Murphy wrote:
> 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 
>> ---
>>   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?

I agree, that would be better. I didn't thought about this option..
Thanks for reporting this.


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

[Robin Murphy]

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 
---
  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, , 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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