From bb20f408662c7bea717fb2c3721e58704e7735d2 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@google.com>
Date: Fri, 20 Jan 2012 14:34:19 -0800
Subject: [PATCH] --- yaml --- r: 286605 b: refs/heads/master c:
 85046579bde15e532983438f86b36856e358f417 h: refs/heads/master i:   286603:
 e7a8d639cd6679fedb457875b9f7dfc0e98e5cd7 v: v3

---
 [refs]            |  2 +-
 trunk/ipc/shm.c   | 37 ++++++++++++++++++++++---------------
 trunk/mm/shmem.c  |  7 -------
 trunk/mm/vmscan.c | 12 +++++++++++-
 4 files changed, 34 insertions(+), 24 deletions(-)

diff --git a/[refs] b/[refs]
index 900c153b928a..ad291fb7f3a0 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: cb78edfdcef5259ac9e9088bd63810d21299928d
+refs/heads/master: 85046579bde15e532983438f86b36856e358f417
diff --git a/trunk/ipc/shm.c b/trunk/ipc/shm.c
index 02ecf2c078fc..854ab58e5f6e 100644
--- a/trunk/ipc/shm.c
+++ b/trunk/ipc/shm.c
@@ -870,9 +870,7 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
 	case SHM_LOCK:
 	case SHM_UNLOCK:
 	{
-		struct file *uninitialized_var(shm_file);
-
-		lru_add_drain_all();  /* drain pagevecs to lru lists */
+		struct file *shm_file;
 
 		shp = shm_lock_check(ns, shmid);
 		if (IS_ERR(shp)) {
@@ -895,22 +893,31 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
 		err = security_shm_shmctl(shp, cmd);
 		if (err)
 			goto out_unlock;
-		
-		if(cmd==SHM_LOCK) {
+
+		shm_file = shp->shm_file;
+		if (is_file_hugepages(shm_file))
+			goto out_unlock;
+
+		if (cmd == SHM_LOCK) {
 			struct user_struct *user = current_user();
-			if (!is_file_hugepages(shp->shm_file)) {
-				err = shmem_lock(shp->shm_file, 1, user);
-				if (!err && !(shp->shm_perm.mode & SHM_LOCKED)){
-					shp->shm_perm.mode |= SHM_LOCKED;
-					shp->mlock_user = user;
-				}
+			err = shmem_lock(shm_file, 1, user);
+			if (!err && !(shp->shm_perm.mode & SHM_LOCKED)) {
+				shp->shm_perm.mode |= SHM_LOCKED;
+				shp->mlock_user = user;
 			}
-		} else if (!is_file_hugepages(shp->shm_file)) {
-			shmem_lock(shp->shm_file, 0, shp->mlock_user);
-			shp->shm_perm.mode &= ~SHM_LOCKED;
-			shp->mlock_user = NULL;
+			goto out_unlock;
 		}
+
+		/* SHM_UNLOCK */
+		if (!(shp->shm_perm.mode & SHM_LOCKED))
+			goto out_unlock;
+		shmem_lock(shm_file, 0, shp->mlock_user);
+		shp->shm_perm.mode &= ~SHM_LOCKED;
+		shp->mlock_user = NULL;
+		get_file(shm_file);
 		shm_unlock(shp);
+		scan_mapping_unevictable_pages(shm_file->f_mapping);
+		fput(shm_file);
 		goto out;
 	}
 	case IPC_RMID:
diff --git a/trunk/mm/shmem.c b/trunk/mm/shmem.c
index feead1943d92..4aaa53abe302 100644
--- a/trunk/mm/shmem.c
+++ b/trunk/mm/shmem.c
@@ -1068,13 +1068,6 @@ int shmem_lock(struct file *file, int lock, struct user_struct *user)
 		user_shm_unlock(inode->i_size, user);
 		info->flags &= ~VM_LOCKED;
 		mapping_clear_unevictable(file->f_mapping);
-		/*
-		 * Ensure that a racing putback_lru_page() can see
-		 * the pages of this mapping are evictable when we
-		 * skip them due to !PageLRU during the scan.
-		 */
-		smp_mb__after_clear_bit();
-		scan_mapping_unevictable_pages(file->f_mapping);
 	}
 	retval = 0;
 
diff --git a/trunk/mm/vmscan.c b/trunk/mm/vmscan.c
index 2880396f7953..e097c1026b58 100644
--- a/trunk/mm/vmscan.c
+++ b/trunk/mm/vmscan.c
@@ -3499,6 +3499,7 @@ int page_evictable(struct page *page, struct vm_area_struct *vma)
 	return 1;
 }
 
+#ifdef CONFIG_SHMEM
 /**
  * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
  * @page: page to check evictability and move to appropriate lru list
@@ -3509,6 +3510,8 @@ int page_evictable(struct page *page, struct vm_area_struct *vma)
  *
  * Restrictions: zone->lru_lock must be held, page must be on LRU and must
  * have PageUnevictable set.
+ *
+ * This function is only used for SysV IPC SHM_UNLOCK.
  */
 static void check_move_unevictable_page(struct page *page, struct zone *zone)
 {
@@ -3545,6 +3548,8 @@ static void check_move_unevictable_page(struct page *page, struct zone *zone)
  *
  * Scan all pages in mapping.  Check unevictable pages for
  * evictability and move them to the appropriate zone lru list.
+ *
+ * This function is only used for SysV IPC SHM_UNLOCK.
  */
 void scan_mapping_unevictable_pages(struct address_space *mapping)
 {
@@ -3590,9 +3595,14 @@ void scan_mapping_unevictable_pages(struct address_space *mapping)
 		pagevec_release(&pvec);
 
 		count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
+		cond_resched();
 	}
-
 }
+#else
+void scan_mapping_unevictable_pages(struct address_space *mapping)
+{
+}
+#endif /* CONFIG_SHMEM */
 
 static void warn_scan_unevictable_pages(void)
 {