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>

13 files changed, 251 insertions, 244 deletions

diff --git a/arch/openrisc/kernel/dma.c b/arch/openrisc/kernel/dma.c
index c7812e6effa2..4d5b8bd1d795 100644
--- a/arch/openrisc/kernel/dma.c
+++ b/arch/openrisc/kernel/dma.c
@@ -44,6 +44,10 @@ page_set_nocache(pte_t *pte, unsigned long addr,
         return 0;
 }
 
+static const struct mm_walk_ops set_nocache_walk_ops = {
+        .pte_entry              = page_set_nocache,
+};
+
 static int
 page_clear_nocache(pte_t *pte, unsigned long addr,
                    unsigned long next, struct mm_walk *walk)
@@ -59,6 +63,10 @@ page_clear_nocache(pte_t *pte, unsigned long addr,
         return 0;
 }
 
+static const struct mm_walk_ops clear_nocache_walk_ops = {
+        .pte_entry              = page_clear_nocache,
+};
+
 /*
  * Alloc "coherent" memory, which for OpenRISC means simply uncached.
  *
@@ -81,10 +89,6 @@ arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 {
         unsigned long va;
         void *page;
-        struct mm_walk walk = {
-                .pte_entry = page_set_nocache,
-                .mm = &init_mm
-        };
 
         page = alloc_pages_exact(size, gfp | __GFP_ZERO);
         if (!page)
@@ -99,7 +103,8 @@ arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
          * We need to iterate through the pages, clearing the dcache for
          * them and setting the cache-inhibit bit.
          */
-        if (walk_page_range(va, va + size, &walk)) {
+        if (walk_page_range(&init_mm, va, va + size, &set_nocache_walk_ops,
+                        NULL)) {
                 free_pages_exact(page, size);
                 return NULL;
         }
@@ -112,13 +117,10 @@ arch_dma_free(struct device *dev, size_t size, void *vaddr,
                 dma_addr_t dma_handle, unsigned long attrs)
 {
         unsigned long va = (unsigned long)vaddr;
-        struct mm_walk walk = {
-                .pte_entry = page_clear_nocache,
-                .mm = &init_mm
-        };
 
         /* walk_page_range shouldn't be able to fail here */
-        WARN_ON(walk_page_range(va, va + size, &walk));
+        WARN_ON(walk_page_range(&init_mm, va, va + size,
+                        &clear_nocache_walk_ops, NULL));
 
         free_pages_exact(vaddr, size);
 }
diff --git a/arch/powerpc/mm/book3s64/subpage_prot.c b/arch/powerpc/mm/book3s64/subpage_prot.c
index 236f0a861ecc..2ef24a53f4c9 100644
--- a/arch/powerpc/mm/book3s64/subpage_prot.c
+++ b/arch/powerpc/mm/book3s64/subpage_prot.c
@@ -139,14 +139,14 @@ static int subpage_walk_pmd_entry(pmd_t *pmd, unsigned long addr,
         return 0;
 }
 
+static const struct mm_walk_ops subpage_walk_ops = {
+        .pmd_entry      = subpage_walk_pmd_entry,
+};
+
 static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,
                                     unsigned long len)
 {
         struct vm_area_struct *vma;
-        struct mm_walk subpage_proto_walk = {
-                .mm = mm,
-                .pmd_entry = subpage_walk_pmd_entry,
-        };
 
         /*
          * We don't try too hard, we just mark all the vma in that range
@@ -163,7 +163,7 @@ static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,
                 if (vma->vm_start >= (addr + len))
                         break;
                 vma->vm_flags |= VM_NOHUGEPAGE;
-                walk_page_vma(vma, &subpage_proto_walk);
+                walk_page_vma(vma, &subpage_walk_ops, NULL);
                 vma = vma->vm_next;
         }
 }
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index cf80feae970d..bd78d504fdad 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2521,13 +2521,9 @@ static int __zap_zero_pages(pmd_t *pmd, unsigned long start,
         return 0;
 }
 
-static inline void zap_zero_pages(struct mm_struct *mm)
-{
-        struct mm_walk walk = { .pmd_entry = __zap_zero_pages };
-
-        walk.mm = mm;
-        walk_page_range(0, TASK_SIZE, &walk);
-}
+static const struct mm_walk_ops zap_zero_walk_ops = {
+        .pmd_entry      = __zap_zero_pages,
+};
 
 /*
  * switch on pgstes for its userspace process (for kvm)
@@ -2546,7 +2542,7 @@ int s390_enable_sie(void)
         mm->context.has_pgste = 1;
         /* split thp mappings and disable thp for future mappings */
         thp_split_mm(mm);
-        zap_zero_pages(mm);
+        walk_page_range(mm, 0, TASK_SIZE, &zap_zero_walk_ops, NULL);
         up_write(&mm->mmap_sem);
         return 0;
 }
@@ -2589,12 +2585,13 @@ static int __s390_enable_skey_hugetlb(pte_t *pte, unsigned long addr,
         return 0;
 }
 
+static const struct mm_walk_ops enable_skey_walk_ops = {
+        .hugetlb_entry          = __s390_enable_skey_hugetlb,
+        .pte_entry              = __s390_enable_skey_pte,
+};
+
 int s390_enable_skey(void)
 {
-        struct mm_walk walk = {
-                .hugetlb_entry = __s390_enable_skey_hugetlb,
-                .pte_entry = __s390_enable_skey_pte,
-        };
         struct mm_struct *mm = current->mm;
         struct vm_area_struct *vma;
         int rc = 0;
@@ -2614,8 +2611,7 @@ int s390_enable_skey(void)
         }
         mm->def_flags &= ~VM_MERGEABLE;
 
-        walk.mm = mm;
-        walk_page_range(0, TASK_SIZE, &walk);
+        walk_page_range(mm, 0, TASK_SIZE, &enable_skey_walk_ops, NULL);
 
 out_up:
         up_write(&mm->mmap_sem);
@@ -2633,13 +2629,14 @@ static int __s390_reset_cmma(pte_t *pte, unsigned long addr,
         return 0;
 }
 
+static const struct mm_walk_ops reset_cmma_walk_ops = {
+        .pte_entry              = __s390_reset_cmma,
+};
+
 void s390_reset_cmma(struct mm_struct *mm)
 {
-        struct mm_walk walk = { .pte_entry = __s390_reset_cmma };
-
         down_write(&mm->mmap_sem);
-        walk.mm = mm;
-        walk_page_range(0, TASK_SIZE, &walk);
+        walk_page_range(mm, 0, TASK_SIZE, &reset_cmma_walk_ops, NULL);
         up_write(&mm->mmap_sem);
 }
 EXPORT_SYMBOL_GPL(s390_reset_cmma);
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8857da830b86..bf43d1d60059 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -513,7 +513,9 @@ static int smaps_pte_hole(unsigned long addr, unsigned long end,
 
         return 0;
 }
-#endif
+#else
+#define smaps_pte_hole          NULL
+#endif /* CONFIG_SHMEM */
 
 static void smaps_pte_entry(pte_t *pte, unsigned long addr,
                 struct mm_walk *walk)
@@ -729,21 +731,24 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
         }
         return 0;
 }
+#else
+#define smaps_hugetlb_range     NULL
 #endif /* HUGETLB_PAGE */
 
+static const struct mm_walk_ops smaps_walk_ops = {
+        .pmd_entry              = smaps_pte_range,
+        .hugetlb_entry          = smaps_hugetlb_range,
+};
+
+static const struct mm_walk_ops smaps_shmem_walk_ops = {
+        .pmd_entry              = smaps_pte_range,
+        .hugetlb_entry          = smaps_hugetlb_range,
+        .pte_hole               = smaps_pte_hole,
+};
+
 static void smap_gather_stats(struct vm_area_struct *vma,
                              struct mem_size_stats *mss)
 {
-        struct mm_walk smaps_walk = {
-                .pmd_entry = smaps_pte_range,
-#ifdef CONFIG_HUGETLB_PAGE
-                .hugetlb_entry = smaps_hugetlb_range,
-#endif
-                .mm = vma->vm_mm,
-        };
-
-        smaps_walk.private = mss;
-
 #ifdef CONFIG_SHMEM
         /* In case of smaps_rollup, reset the value from previous vma */
         mss->check_shmem_swap = false;
@@ -765,12 +770,13 @@ static void smap_gather_stats(struct vm_area_struct *vma,
                         mss->swap += shmem_swapped;
                 } else {
                         mss->check_shmem_swap = true;
-                        smaps_walk.pte_hole = smaps_pte_hole;
+                        walk_page_vma(vma, &smaps_shmem_walk_ops, mss);
+                        return;
                 }
         }
 #endif
         /* mmap_sem is held in m_start */
-        walk_page_vma(vma, &smaps_walk);
+        walk_page_vma(vma, &smaps_walk_ops, mss);
 }
 
 #define SEQ_PUT_DEC(str, val) \
@@ -1118,6 +1124,11 @@ static int clear_refs_test_walk(unsigned long start, unsigned long end,
         return 0;
 }
 
+static const struct mm_walk_ops clear_refs_walk_ops = {
+        .pmd_entry              = clear_refs_pte_range,
+        .test_walk              = clear_refs_test_walk,
+};
+
 static ssize_t clear_refs_write(struct file *file, const char __user *buf,
                                 size_t count, loff_t *ppos)
 {
@@ -1151,12 +1162,6 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
                 struct clear_refs_private cp = {
                         .type = type,
                 };
-                struct mm_walk clear_refs_walk = {
-                        .pmd_entry = clear_refs_pte_range,
-                        .test_walk = clear_refs_test_walk,
-                        .mm = mm,
-                        .private = &cp,
-                };
 
                 if (type == CLEAR_REFS_MM_HIWATER_RSS) {
                         if (down_write_killable(&mm->mmap_sem)) {
@@ -1217,7 +1222,8 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
                                                 0, NULL, mm, 0, -1UL);
                         mmu_notifier_invalidate_range_start(&range);
                 }
-                walk_page_range(0, mm->highest_vm_end, &clear_refs_walk);
+                walk_page_range(mm, 0, mm->highest_vm_end, &clear_refs_walk_ops,
+                                &cp);
                 if (type == CLEAR_REFS_SOFT_DIRTY)
                         mmu_notifier_invalidate_range_end(&range);
                 tlb_finish_mmu(&tlb, 0, -1);
@@ -1489,8 +1495,16 @@ static int pagemap_hugetlb_range(pte_t *ptep, unsigned long hmask,
 
         return err;
 }
+#else
+#define pagemap_hugetlb_range   NULL
 #endif /* HUGETLB_PAGE */
 
+static const struct mm_walk_ops pagemap_ops = {
+        .pmd_entry      = pagemap_pmd_range,
+        .pte_hole       = pagemap_pte_hole,
+        .hugetlb_entry  = pagemap_hugetlb_range,
+};
+
 /*
  * /proc/pid/pagemap - an array mapping virtual pages to pfns
  *
@@ -1522,7 +1536,6 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
 {
         struct mm_struct *mm = file->private_data;
         struct pagemapread pm;
-        struct mm_walk pagemap_walk = {};
         unsigned long src;
         unsigned long svpfn;
         unsigned long start_vaddr;
@@ -1550,14 +1563,6 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
         if (!pm.buffer)
                 goto out_mm;
 
-        pagemap_walk.pmd_entry = pagemap_pmd_range;
-        pagemap_walk.pte_hole = pagemap_pte_hole;
-#ifdef CONFIG_HUGETLB_PAGE
-        pagemap_walk.hugetlb_entry = pagemap_hugetlb_range;
-#endif
-        pagemap_walk.mm = mm;
-        pagemap_walk.private = ±
-
         src = *ppos;
         svpfn = src / PM_ENTRY_BYTES;
         start_vaddr = svpfn << PAGE_SHIFT;
@@ -1586,7 +1591,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
                 ret = down_read_killable(&mm->mmap_sem);
                 if (ret)
                         goto out_free;
-                ret = walk_page_range(start_vaddr, end, &pagemap_walk);
+                ret = walk_page_range(mm, start_vaddr, end, &pagemap_ops, &pm);
                 up_read(&mm->mmap_sem);
                 start_vaddr = end;
 
@@ -1798,6 +1803,11 @@ static int gather_hugetlb_stats(pte_t *pte, unsigned long hmask,
 }
 #endif
 
+static const struct mm_walk_ops show_numa_ops = {
+        .hugetlb_entry = gather_hugetlb_stats,
+        .pmd_entry = gather_pte_stats,
+};
+
 /*
  * Display pages allocated per node and memory policy via /proc.
  */
@@ -1809,12 +1819,6 @@ static int show_numa_map(struct seq_file *m, void *v)
         struct numa_maps *md = &numa_priv->md;
         struct file *file = vma->vm_file;
         struct mm_struct *mm = vma->vm_mm;
-        struct mm_walk walk = {
-                .hugetlb_entry = gather_hugetlb_stats,
-                .pmd_entry = gather_pte_stats,
-                .private = md,
-                .mm = mm,
-        };
         struct mempolicy *pol;
         char buffer[64];
         int nid;
@@ -1848,7 +1852,7 @@ static int show_numa_map(struct seq_file *m, void *v)
                 seq_puts(m, " huge");
 
         /* mmap_sem is held by m_start */
-        walk_page_vma(vma, &walk);
+        walk_page_vma(vma, &show_numa_ops, md);
 
         if (!md->pages)
                 goto out;
diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h
index df278a94086d..bddd9759bab9 100644
--- a/include/linux/pagewalk.h
+++ b/include/linux/pagewalk.h
@@ -4,31 +4,28 @@
 
 #include <linux/mm.h>
 
+struct mm_walk;
+
 /**
- * mm_walk - callbacks for walk_page_range
- * @pud_entry: if set, called for each non-empty PUD (2nd-level) entry
- *             this handler should only handle pud_trans_huge() puds.
- *             the pmd_entry or pte_entry callbacks will be used for
- *             regular PUDs.
- * @pmd_entry: if set, called for each non-empty PMD (3rd-level) entry
- *             this handler is required to be able to handle
- *             pmd_trans_huge() pmds.  They may simply choose to
- *             split_huge_page() instead of handling it explicitly.
- * @pte_entry: if set, called for each non-empty PTE (4th-level) entry
- * @pte_hole: if set, called for each hole at all levels
- * @hugetlb_entry: if set, called for each hugetlb entry
- * @test_walk: caller specific callback function to determine whether
- *             we walk over the current vma or not. Returning 0
- *             value means "do page table walk over the current vma,"
- *             and a negative one means "abort current page table walk
- *             right now." 1 means "skip the current vma."
- * @mm:        mm_struct representing the target process of page table walk
- * @vma:       vma currently walked (NULL if walking outside vmas)
- * @private:   private data for callbacks' usage
- *
- * (see the comment on walk_page_range() for more details)
+ * mm_walk_ops - callbacks for walk_page_range
+ * @pud_entry:          if set, called for each non-empty PUD (2nd-level) entry
+ *                      this handler should only handle pud_trans_huge() puds.
+ *                      the pmd_entry or pte_entry callbacks will be used for
+ *                      regular PUDs.
+ * @pmd_entry:          if set, called for each non-empty PMD (3rd-level) entry
+ *                      this handler is required to be able to handle
+ *                      pmd_trans_huge() pmds.  They may simply choose to
+ *                      split_huge_page() instead of handling it explicitly.
+ * @pte_entry:          if set, called for each non-empty PTE (4th-level) entry
+ * @pte_hole:           if set, called for each hole at all levels
+ * @hugetlb_entry:      if set, called for each hugetlb entry
+ * @test_walk:          caller specific callback function to determine whether
+ *                      we walk over the current vma or not. Returning 0 means
+ *                      "do page table walk over the current vma", returning
+ *                      a negative value means "abort current page table walk
+ *                      right now" and returning 1 means "skip the current vma"
  */
-struct mm_walk {
+struct mm_walk_ops {
         int (*pud_entry)(pud_t *pud, unsigned long addr,
                          unsigned long next, struct mm_walk *walk);
         int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
@@ -42,13 +39,28 @@ struct mm_walk {
                              struct mm_walk *walk);
         int (*test_walk)(unsigned long addr, unsigned long next,
                         struct mm_walk *walk);
+};
+
+/**
+ * mm_walk - walk_page_range data
+ * @ops:        operation to call during the walk
+ * @mm:         mm_struct representing the target process of page table walk
+ * @vma:        vma currently walked (NULL if walking outside vmas)
+ * @private:    private data for callbacks' usage
+ *
+ * (see the comment on walk_page_range() for more details)
+ */
+struct mm_walk {
+        const struct mm_walk_ops *ops;
         struct mm_struct *mm;
         struct vm_area_struct *vma;
         void *private;
 };
 
-int walk_page_range(unsigned long addr, unsigned long end,
-                struct mm_walk *walk);
-int walk_page_vma(struct vm_area_struct *vma, 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 walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
+                void *private);
 
 #endif /* _LINUX_PAGEWALK_H */
diff --git a/mm/hmm.c b/mm/hmm.c
index 26916ff6c8df..902f5fa6bf93 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 80a78bb16782..afe2b015ea58 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 4c3af5d71ab1..9b2516a76be2 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 3a96def1e796..f000771558d8 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 c9c73a35aca7..9f4ed4e985c1 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 3b051b6ab3fe..f9a9dbe8cd33 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 cc73318dbc25..675e5d34a507 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 8a92a961a2ee..b8762b673a3d 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);
 }