1 files changed, 41 insertions, 5 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 4aaa53abe302..269d049294ab 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -379,7 +379,7 @@ static int shmem_free_swap(struct address_space *mapping,
 /*
  * Pagevec may contain swap entries, so shuffle up pages before releasing.
  */
-static void shmem_pagevec_release(struct pagevec *pvec)
+static void shmem_deswap_pagevec(struct pagevec *pvec)
 {
         int i, j;
 
@@ -389,7 +389,36 @@ static void shmem_pagevec_release(struct pagevec *pvec)
                         pvec->pages[j++] = page;
         }
         pvec->nr = j;
-        pagevec_release(pvec);
+}
+
+/*
+ * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
+ */
+void shmem_unlock_mapping(struct address_space *mapping)
+{
+        struct pagevec pvec;
+        pgoff_t indices[PAGEVEC_SIZE];
+        pgoff_t index = 0;
+
+        pagevec_init(&pvec, 0);
+        /*
+         * Minor point, but we might as well stop if someone else SHM_LOCKs it.
+         */
+        while (!mapping_unevictable(mapping)) {
+                /*
+                 * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
+                 * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
+                 */
+                pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
+                                        PAGEVEC_SIZE, pvec.pages, indices);
+                if (!pvec.nr)
+                        break;
+                index = indices[pvec.nr - 1] + 1;
+                shmem_deswap_pagevec(&pvec);
+                check_move_unevictable_pages(pvec.pages, pvec.nr);
+                pagevec_release(&pvec);
+                cond_resched();
+        }
 }
 
 /*
@@ -440,7 +469,8 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
                         }
                         unlock_page(page);
                 }
-                shmem_pagevec_release(&pvec);
+                shmem_deswap_pagevec(&pvec);
+                pagevec_release(&pvec);
                 mem_cgroup_uncharge_end();
                 cond_resched();
                 index++;
@@ -470,7 +500,8 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
                         continue;
                 }
                 if (index == start && indices[0] > end) {
-                        shmem_pagevec_release(&pvec);
+                        shmem_deswap_pagevec(&pvec);
+                        pagevec_release(&pvec);
                         break;
                 }
                 mem_cgroup_uncharge_start();
@@ -494,7 +525,8 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
                         }
                         unlock_page(page);
                 }
-                shmem_pagevec_release(&pvec);
+                shmem_deswap_pagevec(&pvec);
+                pagevec_release(&pvec);
                 mem_cgroup_uncharge_end();
                 index++;
         }
@@ -2438,6 +2470,10 @@ int shmem_lock(struct file *file, int lock, struct user_struct *user)
         return 0;
 }
 
+void shmem_unlock_mapping(struct address_space *mapping)
+{
+}
+
 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
 {
         truncate_inode_pages_range(inode->i_mapping, lstart, lend);