In each rmap traverse case, there is some difference so that we need
function pointers and arguments to them in order to handle these
difference properly.

For this purpose, struct rmap_walk_control is introduced in this patch,
and will be extended in following patch. Introducing and extending are
separate, because it clarify changes.

Signed-off-by: Joonsoo Kim <iamjoonsoo....@lge.com>

diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index 45c9b6a..0eef8cb 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -76,8 +76,7 @@ struct page *ksm_might_need_to_copy(struct page *page,
 int page_referenced_ksm(struct page *page,
                        struct mem_cgroup *memcg, unsigned long *vm_flags);
 int try_to_unmap_ksm(struct page *page, enum ttu_flags flags);
-int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page *,
-                 struct vm_area_struct *, unsigned long, void *), void *arg);
+int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc);
 void ksm_migrate_page(struct page *newpage, struct page *oldpage);
 
 #else  /* !CONFIG_KSM */
@@ -120,8 +119,8 @@ static inline int try_to_unmap_ksm(struct page *page, enum 
ttu_flags flags)
        return 0;
 }
 
-static inline int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct 
page*,
-               struct vm_area_struct *, unsigned long, void *), void *arg)
+static inline int rmap_walk_ksm(struct page *page,
+                       struct rmap_walk_control *rwc)
 {
        return 0;
 }
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 6dacb93..0f65686 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -235,11 +235,16 @@ struct anon_vma *page_lock_anon_vma_read(struct page 
*page);
 void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 
+struct rmap_walk_control {
+       int (*main)(struct page *, struct vm_area_struct *,
+                                       unsigned long, void *);
+       void *arg;      /* argument to main function */
+};
+
 /*
  * Called by migrate.c to remove migration ptes, but might be used more later.
  */
-int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
-               struct vm_area_struct *, unsigned long, void *), void *arg);
+int rmap_walk(struct page *page, struct rmap_walk_control *rwc);
 
 #else  /* !CONFIG_MMU */
 
diff --git a/mm/ksm.c b/mm/ksm.c
index 175fff7..c42ec30 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1997,8 +1997,7 @@ out:
 }
 
 #ifdef CONFIG_MIGRATION
-int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page *,
-                 struct vm_area_struct *, unsigned long, void *), void *arg)
+int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc)
 {
        struct stable_node *stable_node;
        struct rmap_item *rmap_item;
@@ -2033,7 +2032,8 @@ again:
                        if ((rmap_item->mm == vma->vm_mm) == search_new_forks)
                                continue;
 
-                       ret = rmap_one(page, vma, rmap_item->address, arg);
+                       ret = rwc->main(page, vma,
+                                       rmap_item->address, rwc->arg);
                        if (ret != SWAP_AGAIN) {
                                anon_vma_unlock_read(anon_vma);
                                goto out;
diff --git a/mm/migrate.c b/mm/migrate.c
index bb94004..c47425b 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -198,7 +198,12 @@ out:
  */
 static void remove_migration_ptes(struct page *old, struct page *new)
 {
-       rmap_walk(new, remove_migration_pte, old);
+       struct rmap_walk_control rwc;
+
+       memset(&rwc, 0, sizeof(rwc));
+       rwc.main = remove_migration_pte;
+       rwc.arg = old;
+       rmap_walk(new, &rwc);
 }
 
 /*
diff --git a/mm/rmap.c b/mm/rmap.c
index 916f2ed..5933488 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1705,8 +1705,7 @@ static struct anon_vma *rmap_walk_anon_lock(struct page 
*page)
  * rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file():
  * Called by migrate.c to remove migration ptes, but might be used more later.
  */
-static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
-               struct vm_area_struct *, unsigned long, void *), void *arg)
+static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc)
 {
        struct anon_vma *anon_vma;
        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
@@ -1720,7 +1719,7 @@ static int rmap_walk_anon(struct page *page, int 
(*rmap_one)(struct page *,
        anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
                struct vm_area_struct *vma = avc->vma;
                unsigned long address = vma_address(page, vma);
-               ret = rmap_one(page, vma, address, arg);
+               ret = rwc->main(page, vma, address, rwc->arg);
                if (ret != SWAP_AGAIN)
                        break;
        }
@@ -1728,8 +1727,7 @@ static int rmap_walk_anon(struct page *page, int 
(*rmap_one)(struct page *,
        return ret;
 }
 
-static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *,
-               struct vm_area_struct *, unsigned long, void *), void *arg)
+static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
 {
        struct address_space *mapping = page->mapping;
        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
@@ -1745,7 +1743,7 @@ static int rmap_walk_file(struct page *page, int 
(*rmap_one)(struct page *,
        mutex_lock(&mapping->i_mmap_mutex);
        vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
                unsigned long address = vma_address(page, vma);
-               ret = rmap_one(page, vma, address, arg);
+               ret = rwc->main(page, vma, address, rwc->arg);
                if (ret != SWAP_AGAIN)
                        break;
        }
@@ -1758,17 +1756,16 @@ static int rmap_walk_file(struct page *page, int 
(*rmap_one)(struct page *,
        return ret;
 }
 
-int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
-               struct vm_area_struct *, unsigned long, void *), void *arg)
+int rmap_walk(struct page *page, struct rmap_walk_control *rwc)
 {
        VM_BUG_ON(!PageLocked(page));
 
        if (unlikely(PageKsm(page)))
-               return rmap_walk_ksm(page, rmap_one, arg);
+               return rmap_walk_ksm(page, rwc);
        else if (PageAnon(page))
-               return rmap_walk_anon(page, rmap_one, arg);
+               return rmap_walk_anon(page, rwc);
        else
-               return rmap_walk_file(page, rmap_one, arg);
+               return rmap_walk_file(page, rwc);
 }
 #endif /* CONFIG_MIGRATION */
 
-- 
1.7.9.5

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