1 files changed, 36 insertions, 15 deletions

diff --git a/fs/super.c b/fs/super.c
index 938119ab8dcb..9674ab2c8718 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -305,8 +305,13 @@ retry:
 			if (s) {
 				up_write(&s->s_umount);
 				destroy_super(s);
+				s = NULL;
 			}
 			down_write(&old->s_umount);
+			if (unlikely(!(old->s_flags & MS_BORN))) {
+				deactivate_locked_super(old);
+				goto retry;
+			}
 			return old;
 		}
 	}
@@ -358,10 +363,10 @@ EXPORT_SYMBOL(drop_super);
  */
 void sync_supers(void)
 {
-	struct super_block *sb, *n;
+	struct super_block *sb, *p = NULL;
 
 	spin_lock(&sb_lock);
-	list_for_each_entry_safe(sb, n, &super_blocks, s_list) {
+	list_for_each_entry(sb, &super_blocks, s_list) {
 		if (list_empty(&sb->s_instances))
 			continue;
 		if (sb->s_op->write_super && sb->s_dirt) {
@@ -374,11 +379,13 @@ void sync_supers(void)
 			up_read(&sb->s_umount);
 
 			spin_lock(&sb_lock);
-			/* lock was dropped, must reset next */
-			list_safe_reset_next(sb, n, s_list);
-			__put_super(sb);
+			if (p)
+				__put_super(p);
+			p = sb;
 		}
 	}
+	if (p)
+		__put_super(p);
 	spin_unlock(&sb_lock);
 }
 
@@ -392,10 +399,10 @@ void sync_supers(void)
  */
 void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
 {
-	struct super_block *sb, *n;
+	struct super_block *sb, *p = NULL;
 
 	spin_lock(&sb_lock);
-	list_for_each_entry_safe(sb, n, &super_blocks, s_list) {
+	list_for_each_entry(sb, &super_blocks, s_list) {
 		if (list_empty(&sb->s_instances))
 			continue;
 		sb->s_count++;
@@ -407,10 +414,12 @@ void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
 		up_read(&sb->s_umount);
 
 		spin_lock(&sb_lock);
-		/* lock was dropped, must reset next */
-		list_safe_reset_next(sb, n, s_list);
-		__put_super(sb);
+		if (p)
+			__put_super(p);
+		p = sb;
 	}
+	if (p)
+		__put_super(p);
 	spin_unlock(&sb_lock);
 }
 
@@ -572,10 +581,10 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 
 static void do_emergency_remount(struct work_struct *work)
 {
-	struct super_block *sb, *n;
+	struct super_block *sb, *p = NULL;
 
 	spin_lock(&sb_lock);
-	list_for_each_entry_safe(sb, n, &super_blocks, s_list) {
+	list_for_each_entry(sb, &super_blocks, s_list) {
 		if (list_empty(&sb->s_instances))
 			continue;
 		sb->s_count++;
@@ -589,10 +598,12 @@ static void do_emergency_remount(struct work_struct *work)
 		}
 		up_write(&sb->s_umount);
 		spin_lock(&sb_lock);
-		/* lock was dropped, must reset next */
-		list_safe_reset_next(sb, n, s_list);
-		__put_super(sb);
+		if (p)
+			__put_super(p);
+		p = sb;
 	}
+	if (p)
+		__put_super(p);
 	spin_unlock(&sb_lock);
 	kfree(work);
 	printk("Emergency Remount complete\n");
@@ -773,7 +784,16 @@ int get_sb_bdev(struct file_system_type *fs_type,
 			goto error_bdev;
 		}
 
+		/*
+		 * s_umount nests inside bd_mutex during
+		 * __invalidate_device().  close_bdev_exclusive()
+		 * acquires bd_mutex and can't be called under
+		 * s_umount.  Drop s_umount temporarily.  This is safe
+		 * as we're holding an active reference.
+		 */
+		up_write(&s->s_umount);
 		close_bdev_exclusive(bdev, mode);
+		down_write(&s->s_umount);
 	} else {
 		char b[BDEVNAME_SIZE];
 
@@ -909,6 +929,7 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
 		goto out_free_secdata;
 	BUG_ON(!mnt->mnt_sb);
 	WARN_ON(!mnt->mnt_sb->s_bdi);
+	mnt->mnt_sb->s_flags |= MS_BORN;
 
 	error = security_sb_kern_mount(mnt->mnt_sb, flags, secdata);
 	if (error)