pagewalk: separate function pointers from iterator data

The mm_walk structure currently mixed data and code.  Split out the
operations vectors into a new mm_walk_ops structure, and while we are
changing the API also declare the mm_walk structure inside the
walk_page_range and walk_page_vma functions.

Based on patch from Linus Torvalds.

Link: https://lore.kernel.org/r/20190828141955.22210-3-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

8 files changed, 140 insertions, 148 deletions

diff --git a/mm/hmm.c b/mm/hmm.c
index 26916ff6c8df2d..902f5fa6bf93ad 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -852,6 +852,13 @@ void hmm_range_unregister(struct hmm_range *range)
 }
 EXPORT_SYMBOL(hmm_range_unregister);
 
+static const struct mm_walk_ops hmm_walk_ops = {
+	.pud_entry	= hmm_vma_walk_pud,
+	.pmd_entry	= hmm_vma_walk_pmd,
+	.pte_hole	= hmm_vma_walk_hole,
+	.hugetlb_entry	= hmm_vma_walk_hugetlb_entry,
+};
+
 /**
  * hmm_range_fault - try to fault some address in a virtual address range
  * @range:	range being faulted
@@ -887,7 +894,6 @@ long hmm_range_fault(struct hmm_range *range, unsigned int flags)
 	struct hmm_vma_walk hmm_vma_walk;
 	struct hmm *hmm = range->hmm;
 	struct vm_area_struct *vma;
-	struct mm_walk mm_walk;
 	int ret;
 
 	lockdep_assert_held(&hmm->mmu_notifier.mm->mmap_sem);
@@ -916,21 +922,14 @@ long hmm_range_fault(struct hmm_range *range, unsigned int flags)
 		hmm_vma_walk.last = start;
 		hmm_vma_walk.flags = flags;
 		hmm_vma_walk.range = range;
-		mm_walk.private = &hmm_vma_walk;
 		end = min(range->end, vma->vm_end);
 
-		mm_walk.vma = vma;
-		mm_walk.mm = vma->vm_mm;
-		mm_walk.pte_entry = NULL;
-		mm_walk.test_walk = NULL;
-		mm_walk.hugetlb_entry = NULL;
-		mm_walk.pud_entry = hmm_vma_walk_pud;
-		mm_walk.pmd_entry = hmm_vma_walk_pmd;
-		mm_walk.pte_hole = hmm_vma_walk_hole;
-		mm_walk.hugetlb_entry = hmm_vma_walk_hugetlb_entry;
+		walk_page_range(vma->vm_mm, start, end, &hmm_walk_ops,
+				&hmm_vma_walk);
 
 		do {
-			ret = walk_page_range(start, end, &mm_walk);
+			ret = walk_page_range(vma->vm_mm, start, end,
+					&hmm_walk_ops, &hmm_vma_walk);
 			start = hmm_vma_walk.last;
 
 			/* Keep trying while the range is valid. */
diff --git a/mm/madvise.c b/mm/madvise.c
index 80a78bb16782d5..afe2b015ea58a3 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -226,19 +226,9 @@ static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
 	return 0;
 }
 
-static void force_swapin_readahead(struct vm_area_struct *vma,
-		unsigned long start, unsigned long end)
-{
-	struct mm_walk walk = {
-		.mm = vma->vm_mm,
-		.pmd_entry = swapin_walk_pmd_entry,
-		.private = vma,
-	};
-
-	walk_page_range(start, end, &walk);
-
-	lru_add_drain();	/* Push any new pages onto the LRU now */
-}
+static const struct mm_walk_ops swapin_walk_ops = {
+	.pmd_entry		= swapin_walk_pmd_entry,
+};
 
 static void force_shm_swapin_readahead(struct vm_area_struct *vma,
 		unsigned long start, unsigned long end,
@@ -280,7 +270,8 @@ static long madvise_willneed(struct vm_area_struct *vma,
 	*prev = vma;
 #ifdef CONFIG_SWAP
 	if (!file) {
-		force_swapin_readahead(vma, start, end);
+		walk_page_range(vma->vm_mm, start, end, &swapin_walk_ops, vma);
+		lru_add_drain(); /* Push any new pages onto the LRU now */
 		return 0;
 	}
 
@@ -441,20 +432,9 @@ next:
 	return 0;
 }
 
-static void madvise_free_page_range(struct mmu_gather *tlb,
-			     struct vm_area_struct *vma,
-			     unsigned long addr, unsigned long end)
-{
-	struct mm_walk free_walk = {
-		.pmd_entry = madvise_free_pte_range,
-		.mm = vma->vm_mm,
-		.private = tlb,
-	};
-
-	tlb_start_vma(tlb, vma);
-	walk_page_range(addr, end, &free_walk);
-	tlb_end_vma(tlb, vma);
-}
+static const struct mm_walk_ops madvise_free_walk_ops = {
+	.pmd_entry		= madvise_free_pte_range,
+};
 
 static int madvise_free_single_vma(struct vm_area_struct *vma,
 			unsigned long start_addr, unsigned long end_addr)
@@ -481,7 +461,10 @@ static int madvise_free_single_vma(struct vm_area_struct *vma,
 	update_hiwater_rss(mm);
 
 	mmu_notifier_invalidate_range_start(&range);
-	madvise_free_page_range(&tlb, vma, range.start, range.end);
+	tlb_start_vma(&tlb, vma);
+	walk_page_range(vma->vm_mm, range.start, range.end,
+			&madvise_free_walk_ops, &tlb);
+	tlb_end_vma(&tlb, vma);
 	mmu_notifier_invalidate_range_end(&range);
 	tlb_finish_mmu(&tlb, range.start, range.end);
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4c3af5d71ab113..9b2516a76be234 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5283,17 +5283,16 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
 	return 0;
 }
 
+static const struct mm_walk_ops precharge_walk_ops = {
+	.pmd_entry	= mem_cgroup_count_precharge_pte_range,
+};
+
 static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm)
 {
 	unsigned long precharge;
 
-	struct mm_walk mem_cgroup_count_precharge_walk = {
-		.pmd_entry = mem_cgroup_count_precharge_pte_range,
-		.mm = mm,
-	};
 	down_read(&mm->mmap_sem);
-	walk_page_range(0, mm->highest_vm_end,
-			&mem_cgroup_count_precharge_walk);
+	walk_page_range(mm, 0, mm->highest_vm_end, &precharge_walk_ops, NULL);
 	up_read(&mm->mmap_sem);
 
 	precharge = mc.precharge;
@@ -5562,13 +5561,12 @@ put:			/* get_mctgt_type() gets the page */
 	return ret;
 }
 
+static const struct mm_walk_ops charge_walk_ops = {
+	.pmd_entry	= mem_cgroup_move_charge_pte_range,
+};
+
 static void mem_cgroup_move_charge(void)
 {
-	struct mm_walk mem_cgroup_move_charge_walk = {
-		.pmd_entry = mem_cgroup_move_charge_pte_range,
-		.mm = mc.mm,
-	};
-
 	lru_add_drain_all();
 	/*
 	 * Signal lock_page_memcg() to take the memcg's move_lock
@@ -5594,7 +5592,8 @@ retry:
 	 * When we have consumed all precharges and failed in doing
 	 * additional charge, the page walk just aborts.
 	 */
-	walk_page_range(0, mc.mm->highest_vm_end, &mem_cgroup_move_charge_walk);
+	walk_page_range(mc.mm, 0, mc.mm->highest_vm_end, &charge_walk_ops,
+			NULL);
 
 	up_read(&mc.mm->mmap_sem);
 	atomic_dec(&mc.from->moving_account);
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 3a96def1e796dd..f000771558d882 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -655,6 +655,12 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end,
 	return 1;
 }
 
+static const struct mm_walk_ops queue_pages_walk_ops = {
+	.hugetlb_entry		= queue_pages_hugetlb,
+	.pmd_entry		= queue_pages_pte_range,
+	.test_walk		= queue_pages_test_walk,
+};
+
 /*
  * Walk through page tables and collect pages to be migrated.
  *
@@ -679,15 +685,8 @@ queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end,
 		.nmask = nodes,
 		.prev = NULL,
 	};
-	struct mm_walk queue_pages_walk = {
-		.hugetlb_entry = queue_pages_hugetlb,
-		.pmd_entry = queue_pages_pte_range,
-		.test_walk = queue_pages_test_walk,
-		.mm = mm,
-		.private = &qp,
-	};
 
-	return walk_page_range(start, end, &queue_pages_walk);
+	return walk_page_range(mm, start, end, &queue_pages_walk_ops, &qp);
 }
 
 /*
diff --git a/mm/migrate.c b/mm/migrate.c
index c9c73a35aca76d..9f4ed4e985c1fe 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2320,6 +2320,11 @@ next:
 	return 0;
 }
 
+static const struct mm_walk_ops migrate_vma_walk_ops = {
+	.pmd_entry		= migrate_vma_collect_pmd,
+	.pte_hole		= migrate_vma_collect_hole,
+};
+
 /*
  * migrate_vma_collect() - collect pages over a range of virtual addresses
  * @migrate: migrate struct containing all migration information
@@ -2331,21 +2336,15 @@ next:
 static void migrate_vma_collect(struct migrate_vma *migrate)
 {
 	struct mmu_notifier_range range;
-	struct mm_walk mm_walk = {
-		.pmd_entry = migrate_vma_collect_pmd,
-		.pte_hole = migrate_vma_collect_hole,
-		.vma = migrate->vma,
-		.mm = migrate->vma->vm_mm,
-		.private = migrate,
-	};
 
-	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm_walk.mm,
-				migrate->start,
-				migrate->end);
+	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL,
+			migrate->vma->vm_mm, migrate->start, migrate->end);
 	mmu_notifier_invalidate_range_start(&range);
-	walk_page_range(migrate->start, migrate->end, &mm_walk);
-	mmu_notifier_invalidate_range_end(&range);
 
+	walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
+			&migrate_vma_walk_ops, migrate);
+
+	mmu_notifier_invalidate_range_end(&range);
 	migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
 }
 
diff --git a/mm/mincore.c b/mm/mincore.c
index 3b051b6ab3fec6..f9a9dbe8cd3301 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -193,6 +193,12 @@ static inline bool can_do_mincore(struct vm_area_struct *vma)
 		inode_permission(file_inode(vma->vm_file), MAY_WRITE) == 0;
 }
 
+static const struct mm_walk_ops mincore_walk_ops = {
+	.pmd_entry		= mincore_pte_range,
+	.pte_hole		= mincore_unmapped_range,
+	.hugetlb_entry		= mincore_hugetlb,
+};
+
 /*
  * Do a chunk of "sys_mincore()". We've already checked
  * all the arguments, we hold the mmap semaphore: we should
@@ -203,12 +209,6 @@ static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *v
 	struct vm_area_struct *vma;
 	unsigned long end;
 	int err;
-	struct mm_walk mincore_walk = {
-		.pmd_entry = mincore_pte_range,
-		.pte_hole = mincore_unmapped_range,
-		.hugetlb_entry = mincore_hugetlb,
-		.private = vec,
-	};
 
 	vma = find_vma(current->mm, addr);
 	if (!vma || addr < vma->vm_start)
@@ -219,8 +219,7 @@ static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *v
 		memset(vec, 1, pages);
 		return pages;
 	}
-	mincore_walk.mm = vma->vm_mm;
-	err = walk_page_range(addr, end, &mincore_walk);
+	err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec);
 	if (err < 0)
 		return err;
 	return (end - addr) >> PAGE_SHIFT;
diff --git a/mm/mprotect.c b/mm/mprotect.c
index cc73318dbc2592..675e5d34a50773 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -329,20 +329,11 @@ static int prot_none_test(unsigned long addr, unsigned long next,
 	return 0;
 }
 
-static int prot_none_walk(struct vm_area_struct *vma, unsigned long start,
-			   unsigned long end, unsigned long newflags)
-{
-	pgprot_t new_pgprot = vm_get_page_prot(newflags);
-	struct mm_walk prot_none_walk = {
-		.pte_entry = prot_none_pte_entry,
-		.hugetlb_entry = prot_none_hugetlb_entry,
-		.test_walk = prot_none_test,
-		.mm = current->mm,
-		.private = &new_pgprot,
-	};
-
-	return walk_page_range(start, end, &prot_none_walk);
-}
+static const struct mm_walk_ops prot_none_walk_ops = {
+	.pte_entry		= prot_none_pte_entry,
+	.hugetlb_entry		= prot_none_hugetlb_entry,
+	.test_walk		= prot_none_test,
+};
 
 int
 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
@@ -369,7 +360,10 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
 	if (arch_has_pfn_modify_check() &&
 	    (vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 	    (newflags & (VM_READ|VM_WRITE|VM_EXEC)) == 0) {
-		error = prot_none_walk(vma, start, end, newflags);
+		pgprot_t new_pgprot = vm_get_page_prot(newflags);
+
+		error = walk_page_range(current->mm, start, end,
+				&prot_none_walk_ops, &new_pgprot);
 		if (error)
 			return error;
 	}
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 8a92a961a2ee4a..b8762b673a3d4c 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -9,10 +9,11 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 {
 	pte_t *pte;
 	int err = 0;
+	const struct mm_walk_ops *ops = walk->ops;
 
 	pte = pte_offset_map(pmd, addr);
 	for (;;) {
-		err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
+		err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
 		if (err)
 		       break;
 		addr += PAGE_SIZE;
@@ -30,6 +31,7 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 {
 	pmd_t *pmd;
 	unsigned long next;
+	const struct mm_walk_ops *ops = walk->ops;
 	int err = 0;
 
 	pmd = pmd_offset(pud, addr);
@@ -37,8 +39,8 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 again:
 		next = pmd_addr_end(addr, end);
 		if (pmd_none(*pmd) || !walk->vma) {
-			if (walk->pte_hole)
-				err = walk->pte_hole(addr, next, walk);
+			if (ops->pte_hole)
+				err = ops->pte_hole(addr, next, walk);
 			if (err)
 				break;
 			continue;
@@ -47,8 +49,8 @@ again:
 		 * This implies that each ->pmd_entry() handler
 		 * needs to know about pmd_trans_huge() pmds
 		 */
-		if (walk->pmd_entry)
-			err = walk->pmd_entry(pmd, addr, next, walk);
+		if (ops->pmd_entry)
+			err = ops->pmd_entry(pmd, addr, next, walk);
 		if (err)
 			break;
 
@@ -56,7 +58,7 @@ again:
 		 * Check this here so we only break down trans_huge
 		 * pages when we _need_ to
 		 */
-		if (!walk->pte_entry)
+		if (!ops->pte_entry)
 			continue;
 
 		split_huge_pmd(walk->vma, pmd, addr);
@@ -75,6 +77,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
 {
 	pud_t *pud;
 	unsigned long next;
+	const struct mm_walk_ops *ops = walk->ops;
 	int err = 0;
 
 	pud = pud_offset(p4d, addr);
@@ -82,18 +85,18 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
  again:
 		next = pud_addr_end(addr, end);
 		if (pud_none(*pud) || !walk->vma) {
-			if (walk->pte_hole)
-				err = walk->pte_hole(addr, next, walk);
+			if (ops->pte_hole)
+				err = ops->pte_hole(addr, next, walk);
 			if (err)
 				break;
 			continue;
 		}
 
-		if (walk->pud_entry) {
+		if (ops->pud_entry) {
 			spinlock_t *ptl = pud_trans_huge_lock(pud, walk->vma);
 
 			if (ptl) {
-				err = walk->pud_entry(pud, addr, next, walk);
+				err = ops->pud_entry(pud, addr, next, walk);
 				spin_unlock(ptl);
 				if (err)
 					break;
@@ -105,7 +108,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
 		if (pud_none(*pud))
 			goto again;
 
-		if (walk->pmd_entry || walk->pte_entry)
+		if (ops->pmd_entry || ops->pte_entry)
 			err = walk_pmd_range(pud, addr, next, walk);
 		if (err)
 			break;
@@ -119,19 +122,20 @@ static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
 {
 	p4d_t *p4d;
 	unsigned long next;
+	const struct mm_walk_ops *ops = walk->ops;
 	int err = 0;
 
 	p4d = p4d_offset(pgd, addr);
 	do {
 		next = p4d_addr_end(addr, end);
 		if (p4d_none_or_clear_bad(p4d)) {
-			if (walk->pte_hole)
-				err = walk->pte_hole(addr, next, walk);
+			if (ops->pte_hole)
+				err = ops->pte_hole(addr, next, walk);
 			if (err)
 				break;
 			continue;
 		}
-		if (walk->pmd_entry || walk->pte_entry)
+		if (ops->pmd_entry || ops->pte_entry)
 			err = walk_pud_range(p4d, addr, next, walk);
 		if (err)
 			break;
@@ -145,19 +149,20 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
 {
 	pgd_t *pgd;
 	unsigned long next;
+	const struct mm_walk_ops *ops = walk->ops;
 	int err = 0;
 
 	pgd = pgd_offset(walk->mm, addr);
 	do {
 		next = pgd_addr_end(addr, end);
 		if (pgd_none_or_clear_bad(pgd)) {
-			if (walk->pte_hole)
-				err = walk->pte_hole(addr, next, walk);
+			if (ops->pte_hole)
+				err = ops->pte_hole(addr, next, walk);
 			if (err)
 				break;
 			continue;
 		}
-		if (walk->pmd_entry || walk->pte_entry)
+		if (ops->pmd_entry || ops->pte_entry)
 			err = walk_p4d_range(pgd, addr, next, walk);
 		if (err)
 			break;
@@ -183,6 +188,7 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
 	unsigned long hmask = huge_page_mask(h);
 	unsigned long sz = huge_page_size(h);
 	pte_t *pte;
+	const struct mm_walk_ops *ops = walk->ops;
 	int err = 0;
 
 	do {
@@ -190,9 +196,9 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
 		pte = huge_pte_offset(walk->mm, addr & hmask, sz);
 
 		if (pte)
-			err = walk->hugetlb_entry(pte, hmask, addr, next, walk);
-		else if (walk->pte_hole)
-			err = walk->pte_hole(addr, next, walk);
+			err = ops->hugetlb_entry(pte, hmask, addr, next, walk);
+		else if (ops->pte_hole)
+			err = ops->pte_hole(addr, next, walk);
 
 		if (err)
 			break;
@@ -220,9 +226,10 @@ static int walk_page_test(unsigned long start, unsigned long end,
 			struct mm_walk *walk)
 {
 	struct vm_area_struct *vma = walk->vma;
+	const struct mm_walk_ops *ops = walk->ops;
 
-	if (walk->test_walk)
-		return walk->test_walk(start, end, walk);
+	if (ops->test_walk)
+		return ops->test_walk(start, end, walk);
 
 	/*
 	 * vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP
@@ -234,8 +241,8 @@ static int walk_page_test(unsigned long start, unsigned long end,
 	 */
 	if (vma->vm_flags & VM_PFNMAP) {
 		int err = 1;
-		if (walk->pte_hole)
-			err = walk->pte_hole(start, end, walk);
+		if (ops->pte_hole)
+			err = ops->pte_hole(start, end, walk);
 		return err ? err : 1;
 	}
 	return 0;
@@ -248,7 +255,7 @@ static int __walk_page_range(unsigned long start, unsigned long end,
 	struct vm_area_struct *vma = walk->vma;
 
 	if (vma && is_vm_hugetlb_page(vma)) {
-		if (walk->hugetlb_entry)
+		if (walk->ops->hugetlb_entry)
 			err = walk_hugetlb_range(start, end, walk);
 	} else
 		err = walk_pgd_range(start, end, walk);
@@ -258,11 +265,13 @@ static int __walk_page_range(unsigned long start, unsigned long end,
 
 /**
  * walk_page_range - walk page table with caller specific callbacks
- * @start: start address of the virtual address range
- * @end: end address of the virtual address range
- * @walk: mm_walk structure defining the callbacks and the target address space
+ * @mm:		mm_struct representing the target process of page table walk
+ * @start:	start address of the virtual address range
+ * @end:	end address of the virtual address range
+ * @ops:	operation to call during the walk
+ * @private:	private data for callbacks' usage
  *
- * Recursively walk the page table tree of the process represented by @walk->mm
+ * Recursively walk the page table tree of the process represented by @mm
  * within the virtual address range [@start, @end). During walking, we can do
  * some caller-specific works for each entry, by setting up pmd_entry(),
  * pte_entry(), and/or hugetlb_entry(). If you don't set up for some of these
@@ -278,47 +287,52 @@ static int __walk_page_range(unsigned long start, unsigned long end,
  *
  * Before starting to walk page table, some callers want to check whether
  * they really want to walk over the current vma, typically by checking
- * its vm_flags. walk_page_test() and @walk->test_walk() are used for this
+ * its vm_flags. walk_page_test() and @ops->test_walk() are used for this
  * purpose.
  *
  * struct mm_walk keeps current values of some common data like vma and pmd,
  * which are useful for the access from callbacks. If you want to pass some
- * caller-specific data to callbacks, @walk->private should be helpful.
+ * caller-specific data to callbacks, @private should be helpful.
  *
  * Locking:
- *   Callers of walk_page_range() and walk_page_vma() should hold
- *   @walk->mm->mmap_sem, because these function traverse vma list and/or
- *   access to vma's data.
+ *   Callers of walk_page_range() and walk_page_vma() should hold @mm->mmap_sem,
+ *   because these function traverse vma list and/or access to vma's data.
  */
-int walk_page_range(unsigned long start, unsigned long end,
-		    struct mm_walk *walk)
+int walk_page_range(struct mm_struct *mm, unsigned long start,
+		unsigned long end, const struct mm_walk_ops *ops,
+		void *private)
 {
 	int err = 0;
 	unsigned long next;
 	struct vm_area_struct *vma;
+	struct mm_walk walk = {
+		.ops		= ops,
+		.mm		= mm,
+		.private	= private,
+	};
 
 	if (start >= end)
 		return -EINVAL;
 
-	if (!walk->mm)
+	if (!walk.mm)
 		return -EINVAL;
 
-	VM_BUG_ON_MM(!rwsem_is_locked(&walk->mm->mmap_sem), walk->mm);
+	VM_BUG_ON_MM(!rwsem_is_locked(&walk.mm->mmap_sem), walk.mm);
 
-	vma = find_vma(walk->mm, start);
+	vma = find_vma(walk.mm, start);
 	do {
 		if (!vma) { /* after the last vma */
-			walk->vma = NULL;
+			walk.vma = NULL;
 			next = end;
 		} else if (start < vma->vm_start) { /* outside vma */
-			walk->vma = NULL;
+			walk.vma = NULL;
 			next = min(end, vma->vm_start);
 		} else { /* inside vma */
-			walk->vma = vma;
+			walk.vma = vma;
 			next = min(end, vma->vm_end);
 			vma = vma->vm_next;
 
-			err = walk_page_test(start, next, walk);
+			err = walk_page_test(start, next, &walk);
 			if (err > 0) {
 				/*
 				 * positive return values are purely for
@@ -331,28 +345,34 @@ int walk_page_range(unsigned long start, unsigned long end,
 			if (err < 0)
 				break;
 		}
-		if (walk->vma || walk->pte_hole)
-			err = __walk_page_range(start, next, walk);
+		if (walk.vma || walk.ops->pte_hole)
+			err = __walk_page_range(start, next, &walk);
 		if (err)
 			break;
 	} while (start = next, start < end);
 	return err;
 }
 
-int walk_page_vma(struct vm_area_struct *vma, struct mm_walk *walk)
+int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
+		void *private)
 {
+	struct mm_walk walk = {
+		.ops		= ops,
+		.mm		= vma->vm_mm,
+		.vma		= vma,
+		.private	= private,
+	};
 	int err;
 
-	if (!walk->mm)
+	if (!walk.mm)
 		return -EINVAL;
 
-	VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));
-	VM_BUG_ON(!vma);
-	walk->vma = vma;
-	err = walk_page_test(vma->vm_start, vma->vm_end, walk);
+	VM_BUG_ON(!rwsem_is_locked(&vma->vm_mm->mmap_sem));
+
+	err = walk_page_test(vma->vm_start, vma->vm_end, &walk);
 	if (err > 0)
 		return 0;
 	if (err < 0)
 		return err;
-	return __walk_page_range(vma->vm_start, vma->vm_end, walk);
+	return __walk_page_range(vma->vm_start, vma->vm_end, &walk);
 }