mm/rmap: use rmap_walk() in page_referenced()

Now, we have an infrastructure in rmap_walk() to handle difference from
variants of rmap traversing functions.

So, just use it in page_referenced().

In this patch, I change following things.

1. remove some variants of rmap traversing functions.
	cf> page_referenced_ksm, page_referenced_anon,
	page_referenced_file

2. introduce new struct page_referenced_arg and pass it to
   page_referenced_one(), main function of rmap_walk, in order to count
   reference, to store vm_flags and to check finish condition.

3. mechanical change to use rmap_walk() in page_referenced().

[liwanp@linux.vnet.ibm.com: fix BUG at rmap_walk]
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 80 insertions, 194 deletions

diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index 91b9719722c3..3be6bb18562d 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -73,8 +73,6 @@ static inline void set_page_stable_node(struct page *page,
 struct page *ksm_might_need_to_copy(struct page *page,
                         struct vm_area_struct *vma, unsigned long address);
 
-int page_referenced_ksm(struct page *page,
-                        struct mem_cgroup *memcg, unsigned long *vm_flags);
 int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc);
 void ksm_migrate_page(struct page *newpage, struct page *oldpage);
 
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 2462458708cd..1da693d51255 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -184,7 +184,7 @@ static inline void page_dup_rmap(struct page *page)
 int page_referenced(struct page *, int is_locked,
                         struct mem_cgroup *memcg, unsigned long *vm_flags);
 int page_referenced_one(struct page *, struct vm_area_struct *,
-        unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
+        unsigned long address, void *arg);
 
 #define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
 
diff --git a/mm/ksm.c b/mm/ksm.c
index 646d45a6b6c8..3df141e5f3e0 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1891,61 +1891,6 @@ struct page *ksm_might_need_to_copy(struct page *page,
         return new_page;
 }
 
-int page_referenced_ksm(struct page *page, struct mem_cgroup *memcg,
-                        unsigned long *vm_flags)
-{
-        struct stable_node *stable_node;
-        struct rmap_item *rmap_item;
-        unsigned int mapcount = page_mapcount(page);
-        int referenced = 0;
-        int search_new_forks = 0;
-
-        VM_BUG_ON(!PageKsm(page));
-        VM_BUG_ON(!PageLocked(page));
-
-        stable_node = page_stable_node(page);
-        if (!stable_node)
-                return 0;
-again:
-        hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) {
-                struct anon_vma *anon_vma = rmap_item->anon_vma;
-                struct anon_vma_chain *vmac;
-                struct vm_area_struct *vma;
-
-                anon_vma_lock_read(anon_vma);
-                anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root,
-                                               0, ULONG_MAX) {
-                        vma = vmac->vma;
-                        if (rmap_item->address < vma->vm_start ||
-                            rmap_item->address >= vma->vm_end)
-                                continue;
-                        /*
-                         * Initially we examine only the vma which covers this
-                         * rmap_item; but later, if there is still work to do,
-                         * we examine covering vmas in other mms: in case they
-                         * were forked from the original since ksmd passed.
-                         */
-                        if ((rmap_item->mm == vma->vm_mm) == search_new_forks)
-                                continue;
-
-                        if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
-                                continue;
-
-                        referenced += page_referenced_one(page, vma,
-                                rmap_item->address, &mapcount, vm_flags);
-                        if (!search_new_forks || !mapcount)
-                                break;
-                }
-                anon_vma_unlock_read(anon_vma);
-                if (!mapcount)
-                        goto out;
-        }
-        if (!search_new_forks++)
-                goto again;
-out:
-        return referenced;
-}
-
 int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc)
 {
         struct stable_node *stable_node;
@@ -1954,6 +1899,11 @@ int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc)
         int search_new_forks = 0;
 
         VM_BUG_ON(!PageKsm(page));
+
+        /*
+         * Rely on the page lock to protect against concurrent modifications
+         * to that page's node of the stable tree.
+         */
         VM_BUG_ON(!PageLocked(page));
 
         stable_node = page_stable_node(page);
diff --git a/mm/rmap.c b/mm/rmap.c
index c73e0c645d09..080413036406 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -660,17 +660,22 @@ int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
         return 1;
 }
 
+struct page_referenced_arg {
+        int mapcount;
+        int referenced;
+        unsigned long vm_flags;
+        struct mem_cgroup *memcg;
+};
 /*
- * Subfunctions of page_referenced: page_referenced_one called
- * repeatedly from either page_referenced_anon or page_referenced_file.
+ * arg: page_referenced_arg will be passed
  */
 int page_referenced_one(struct page *page, struct vm_area_struct *vma,
-                        unsigned long address, unsigned int *mapcount,
-                        unsigned long *vm_flags)
+                        unsigned long address, void *arg)
 {
         struct mm_struct *mm = vma->vm_mm;
         spinlock_t *ptl;
         int referenced = 0;
+        struct page_referenced_arg *pra = arg;
 
         if (unlikely(PageTransHuge(page))) {
                 pmd_t *pmd;
@@ -682,13 +687,12 @@ int page_referenced_one(struct page *page, struct vm_area_struct *vma,
                 pmd = page_check_address_pmd(page, mm, address,
                                              PAGE_CHECK_ADDRESS_PMD_FLAG, &ptl);
                 if (!pmd)
-                        goto out;
+                        return SWAP_AGAIN;
 
                 if (vma->vm_flags & VM_LOCKED) {
                         spin_unlock(ptl);
-                        *mapcount = 0;  /* break early from loop */
-                        *vm_flags |= VM_LOCKED;
-                        goto out;
+                        pra->vm_flags |= VM_LOCKED;
+                        return SWAP_FAIL; /* To break the loop */
                 }
 
                 /* go ahead even if the pmd is pmd_trans_splitting() */
@@ -704,13 +708,12 @@ int page_referenced_one(struct page *page, struct vm_area_struct *vma,
                  */
                 pte = page_check_address(page, mm, address, &ptl, 0);
                 if (!pte)
-                        goto out;
+                        return SWAP_AGAIN;
 
                 if (vma->vm_flags & VM_LOCKED) {
                         pte_unmap_unlock(pte, ptl);
-                        *mapcount = 0;  /* break early from loop */
-                        *vm_flags |= VM_LOCKED;
-                        goto out;
+                        pra->vm_flags |= VM_LOCKED;
+                        return SWAP_FAIL; /* To break the loop */
                 }
 
                 if (ptep_clear_flush_young_notify(vma, address, pte)) {
@@ -727,113 +730,27 @@ int page_referenced_one(struct page *page, struct vm_area_struct *vma,
                 pte_unmap_unlock(pte, ptl);
         }
 
-        (*mapcount)--;
-
-        if (referenced)
-                *vm_flags |= vma->vm_flags;
-out:
-        return referenced;
-}
-
-static int page_referenced_anon(struct page *page,
-                                struct mem_cgroup *memcg,
-                                unsigned long *vm_flags)
-{
-        unsigned int mapcount;
-        struct anon_vma *anon_vma;
-        pgoff_t pgoff;
-        struct anon_vma_chain *avc;
-        int referenced = 0;
-
-        anon_vma = page_lock_anon_vma_read(page);
-        if (!anon_vma)
-                return referenced;
-
-        mapcount = page_mapcount(page);
-        pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
-        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);
-                /*
-                 * If we are reclaiming on behalf of a cgroup, skip
-                 * counting on behalf of references from different
-                 * cgroups
-                 */
-                if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
-                        continue;
-                referenced += page_referenced_one(page, vma, address,
-                                                  &mapcount, vm_flags);
-                if (!mapcount)
-                        break;
+        if (referenced) {
+                pra->referenced++;
+                pra->vm_flags |= vma->vm_flags;
         }
 
-        page_unlock_anon_vma_read(anon_vma);
-        return referenced;
+        pra->mapcount--;
+        if (!pra->mapcount)
+                return SWAP_SUCCESS; /* To break the loop */
+
+        return SWAP_AGAIN;
 }
 
-/**
- * page_referenced_file - referenced check for object-based rmap
- * @page: the page we're checking references on.
- * @memcg: target memory control group
- * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
- *
- * For an object-based mapped page, find all the places it is mapped and
- * check/clear the referenced flag.  This is done by following the page->mapping
- * pointer, then walking the chain of vmas it holds.  It returns the number
- * of references it found.
- *
- * This function is only called from page_referenced for object-based pages.
- */
-static int page_referenced_file(struct page *page,
-                                struct mem_cgroup *memcg,
-                                unsigned long *vm_flags)
+static bool invalid_page_referenced_vma(struct vm_area_struct *vma, void *arg)
 {
-        unsigned int mapcount;
-        struct address_space *mapping = page->mapping;
-        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
-        struct vm_area_struct *vma;
-        int referenced = 0;
-
-        /*
-         * The caller's checks on page->mapping and !PageAnon have made
-         * sure that this is a file page: the check for page->mapping
-         * excludes the case just before it gets set on an anon page.
-         */
-        BUG_ON(PageAnon(page));
+        struct page_referenced_arg *pra = arg;
+        struct mem_cgroup *memcg = pra->memcg;
 
-        /*
-         * The page lock not only makes sure that page->mapping cannot
-         * suddenly be NULLified by truncation, it makes sure that the
-         * structure at mapping cannot be freed and reused yet,
-         * so we can safely take mapping->i_mmap_mutex.
-         */
-        BUG_ON(!PageLocked(page));
-
-        mutex_lock(&mapping->i_mmap_mutex);
-
-        /*
-         * i_mmap_mutex does not stabilize mapcount at all, but mapcount
-         * is more likely to be accurate if we note it after spinning.
-         */
-        mapcount = page_mapcount(page);
-
-        vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
-                unsigned long address = vma_address(page, vma);
-                /*
-                 * If we are reclaiming on behalf of a cgroup, skip
-                 * counting on behalf of references from different
-                 * cgroups
-                 */
-                if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
-                        continue;
-                referenced += page_referenced_one(page, vma, address,
-                                                  &mapcount, vm_flags);
-                if (!mapcount)
-                        break;
-        }
+        if (!mm_match_cgroup(vma->vm_mm, memcg))
+                return true;
 
-        mutex_unlock(&mapping->i_mmap_mutex);
-        return referenced;
+        return false;
 }
 
 /**
@@ -851,32 +768,47 @@ int page_referenced(struct page *page,
                     struct mem_cgroup *memcg,
                     unsigned long *vm_flags)
 {
-        int referenced = 0;
+        int ret;
         int we_locked = 0;
+        struct page_referenced_arg pra = {
+                .mapcount = page_mapcount(page),
+                .memcg = memcg,
+        };
+        struct rmap_walk_control rwc = {
+                .rmap_one = page_referenced_one,
+                .arg = (void *)&pra,
+                .anon_lock = page_lock_anon_vma_read,
+        };
 
         *vm_flags = 0;
-        if (page_mapped(page) && page_rmapping(page)) {
-                if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
-                        we_locked = trylock_page(page);
-                        if (!we_locked) {
-                                referenced++;
-                                goto out;
-                        }
-                }
-                if (unlikely(PageKsm(page)))
-                        referenced += page_referenced_ksm(page, memcg,
-                                                                vm_flags);
-                else if (PageAnon(page))
-                        referenced += page_referenced_anon(page, memcg,
-                                                                vm_flags);
-                else if (page->mapping)
-                        referenced += page_referenced_file(page, memcg,
-                                                                vm_flags);
-                if (we_locked)
-                        unlock_page(page);
+        if (!page_mapped(page))
+                return 0;
+
+        if (!page_rmapping(page))
+                return 0;
+
+        if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
+                we_locked = trylock_page(page);
+                if (!we_locked)
+                        return 1;
         }
-out:
-        return referenced;
+
+        /*
+         * If we are reclaiming on behalf of a cgroup, skip
+         * counting on behalf of references from different
+         * cgroups
+         */
+        if (memcg) {
+                rwc.invalid_vma = invalid_page_referenced_vma;
+        }
+
+        ret = rmap_walk(page, &rwc);
+        *vm_flags = pra.vm_flags;
+
+        if (we_locked)
+                unlock_page(page);
+
+        return pra.referenced;
 }
 
 static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
@@ -1700,6 +1632,14 @@ static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
         struct vm_area_struct *vma;
         int ret = SWAP_AGAIN;
 
+        /*
+         * The page lock not only makes sure that page->mapping cannot
+         * suddenly be NULLified by truncation, it makes sure that the
+         * structure at mapping cannot be freed and reused yet,
+         * so we can safely take mapping->i_mmap_mutex.
+         */
+        VM_BUG_ON(!PageLocked(page));
+
         if (!mapping)
                 return ret;
         mutex_lock(&mapping->i_mmap_mutex);
@@ -1731,8 +1671,6 @@ done:
 
 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, rwc);
         else if (PageAnon(page))