Remove internal use of 'write_access' in mm/memory.c

The fault handling routines really want more fine-grained flags than a
single "was it a write fault" boolean - the callers will want to set
flags like "you can return a retry error" etc.

And that's actually how the VM works internally, but right now the
top-level fault handling functions in mm/memory.c all pass just the
'write_access' boolean around.

This switches them over to pass around the FAULT_FLAG_xyzzy 'flags'
variable instead.  The 'write_access' calling convention still exists
for the exported 'handle_mm_fault()' function, but that is next.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/memory.c

@@ -2496,7 +2496,7 @@ int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end)
  */
 static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		unsigned long address, pte_t *page_table, pmd_t *pmd,
-		int write_access, pte_t orig_pte)
+		unsigned int flags, pte_t orig_pte)
 {
 	spinlock_t *ptl;
 	struct page *page;
@@ -2572,9 +2572,9 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
 
 	inc_mm_counter(mm, anon_rss);
 	pte = mk_pte(page, vma->vm_page_prot);
-	if (write_access && reuse_swap_page(page)) {
+	if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
 		pte = maybe_mkwrite(pte_mkdirty(pte), vma);
-		write_access = 0;
+		flags &= ~FAULT_FLAG_WRITE;
 	}
 	flush_icache_page(vma, page);
 	set_pte_at(mm, address, page_table, pte);
@@ -2587,7 +2587,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		try_to_free_swap(page);
 	unlock_page(page);
 
-	if (write_access) {
+	if (flags & FAULT_FLAG_WRITE) {
 		ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
 		if (ret & VM_FAULT_ERROR)
 			ret &= VM_FAULT_ERROR;
@@ -2616,7 +2616,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
  */
 static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		unsigned long address, pte_t *page_table, pmd_t *pmd,
-		int write_access)
+		unsigned int flags)
 {
 	struct page *page;
 	spinlock_t *ptl;
@@ -2776,7 +2776,7 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	 * due to the bad i386 page protection. But it's valid
 	 * for other architectures too.
 	 *
-	 * Note that if write_access is true, we either now have
+	 * Note that if FAULT_FLAG_WRITE is set, we either now have
 	 * an exclusive copy of the page, or this is a shared mapping,
 	 * so we can make it writable and dirty to avoid having to
 	 * handle that later.
@@ -2847,11 +2847,10 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 
 static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		unsigned long address, pte_t *page_table, pmd_t *pmd,
-		int write_access, pte_t orig_pte)
+		unsigned int flags, pte_t orig_pte)
 {
 	pgoff_t pgoff = (((address & PAGE_MASK)
 			- vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
-	unsigned int flags = (write_access ? FAULT_FLAG_WRITE : 0);
 
 	pte_unmap(page_table);
 	return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
@@ -2868,12 +2867,12 @@ static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
  */
 static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		unsigned long address, pte_t *page_table, pmd_t *pmd,
-		int write_access, pte_t orig_pte)
+		unsigned int flags, pte_t orig_pte)
 {
-	unsigned int flags = FAULT_FLAG_NONLINEAR |
-				(write_access ? FAULT_FLAG_WRITE : 0);
 	pgoff_t pgoff;
 
+	flags |= FAULT_FLAG_NONLINEAR;
+
 	if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
 		return 0;
 
@@ -2904,7 +2903,7 @@ static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
  */
 static inline int handle_pte_fault(struct mm_struct *mm,
 		struct vm_area_struct *vma, unsigned long address,
-		pte_t *pte, pmd_t *pmd, int write_access)
+		pte_t *pte, pmd_t *pmd, unsigned int flags)
 {
 	pte_t entry;
 	spinlock_t *ptl;
@@ -2915,30 +2914,30 @@ static inline int handle_pte_fault(struct mm_struct *mm,
 			if (vma->vm_ops) {
 				if (likely(vma->vm_ops->fault))
 					return do_linear_fault(mm, vma, address,
-						pte, pmd, write_access, entry);
+						pte, pmd, flags, entry);
 			}
 			return do_anonymous_page(mm, vma, address,
-						 pte, pmd, write_access);
+						 pte, pmd, flags);
 		}
 		if (pte_file(entry))
 			return do_nonlinear_fault(mm, vma, address,
-					pte, pmd, write_access, entry);
+					pte, pmd, flags, entry);
 		return do_swap_page(mm, vma, address,
-					pte, pmd, write_access, entry);
+					pte, pmd, flags, entry);
 	}
 
 	ptl = pte_lockptr(mm, pmd);
 	spin_lock(ptl);
 	if (unlikely(!pte_same(*pte, entry)))
 		goto unlock;
-	if (write_access) {
+	if (flags & FAULT_FLAG_WRITE) {
 		if (!pte_write(entry))
 			return do_wp_page(mm, vma, address,
 					pte, pmd, ptl, entry);
 		entry = pte_mkdirty(entry);
 	}
 	entry = pte_mkyoung(entry);
-	if (ptep_set_access_flags(vma, address, pte, entry, write_access)) {
+	if (ptep_set_access_flags(vma, address, pte, entry, flags & FAULT_FLAG_WRITE)) {
 		update_mmu_cache(vma, address, entry);
 	} else {
 		/*
@@ -2947,7 +2946,7 @@ static inline int handle_pte_fault(struct mm_struct *mm,
 		 * This still avoids useless tlb flushes for .text page faults
 		 * with threads.
 		 */
-		if (write_access)
+		if (flags & FAULT_FLAG_WRITE)
 			flush_tlb_page(vma, address);
 	}
 unlock:
@@ -2965,13 +2964,14 @@ int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;
+	unsigned int flags = write_access ? FAULT_FLAG_WRITE : 0;
 
 	__set_current_state(TASK_RUNNING);
 
 	count_vm_event(PGFAULT);
 
 	if (unlikely(is_vm_hugetlb_page(vma)))
-		return hugetlb_fault(mm, vma, address, write_access);
+		return hugetlb_fault(mm, vma, address, flags);
 
 	pgd = pgd_offset(mm, address);
 	pud = pud_alloc(mm, pgd, address);
@@ -2984,7 +2984,7 @@ int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	if (!pte)
 		return VM_FAULT_OOM;
 
-	return handle_pte_fault(mm, vma, address, pte, pmd, write_access);
+	return handle_pte_fault(mm, vma, address, pte, pmd, flags);
 }
 
 #ifndef __PAGETABLE_PUD_FOLDED