rmap: add exclusive page to private anon_vma on swapin

On swapin it is fairly common for a page to be owned exclusively by one
process.  In that case we want to add the page to the anon_vma of that
process's VMA, instead of to the root anon_vma.

This will reduce the amount of rmap searching that the swapout code needs
to do.

Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 15 insertions, 2 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 6b0c37dcfd16..6bc039486e9f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2628,6 +2628,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
         swp_entry_t entry;
         pte_t pte;
         struct mem_cgroup *ptr = NULL;
+        int exclusive = 0;
         int ret = 0;
 
         if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
@@ -2722,10 +2723,11 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
         if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
                 pte = maybe_mkwrite(pte_mkdirty(pte), vma);
                 flags &= ~FAULT_FLAG_WRITE;
+                exclusive = 1;
         }
         flush_icache_page(vma, page);
         set_pte_at(mm, address, page_table, pte);
-        page_add_anon_rmap(page, vma, address);
+        do_page_add_anon_rmap(page, vma, address, exclusive);
         /* It's better to call commit-charge after rmap is established */
         mem_cgroup_commit_charge_swapin(page, ptr);
 
diff --git a/mm/rmap.c b/mm/rmap.c
index 4d152a6d3a89..a7d0f5482634 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -830,6 +830,17 @@ static void __page_check_anon_rmap(struct page *page,
 void page_add_anon_rmap(struct page *page,
         struct vm_area_struct *vma, unsigned long address)
 {
+        do_page_add_anon_rmap(page, vma, address, 0);
+}
+
+/*
+ * Special version of the above for do_swap_page, which often runs
+ * into pages that are exclusively owned by the current process.
+ * Everybody else should continue to use page_add_anon_rmap above.
+ */
+void do_page_add_anon_rmap(struct page *page,
+        struct vm_area_struct *vma, unsigned long address, int exclusive)
+{
         int first = atomic_inc_and_test(&page->_mapcount);
         if (first)
                 __inc_zone_page_state(page, NR_ANON_PAGES);
@@ -839,7 +850,7 @@ void page_add_anon_rmap(struct page *page,
         VM_BUG_ON(!PageLocked(page));
         VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
         if (first)
-                __page_set_anon_rmap(page, vma, address, 0);
+                __page_set_anon_rmap(page, vma, address, exclusive);
         else
                 __page_check_anon_rmap(page, vma, address);
 }