... and the same for vfsmount id/mount group id

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namespace.c

@@ -42,6 +42,8 @@ __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
 static int event;
 static DEFINE_IDA(mnt_id_ida);
 static DEFINE_IDA(mnt_group_ida);
+static int mnt_id_start = 0;
+static int mnt_group_start = 1;
 
 static struct list_head *mount_hashtable __read_mostly;
 static struct kmem_cache *mnt_cache __read_mostly;
@@ -69,7 +71,9 @@ static int mnt_alloc_id(struct vfsmount *mnt)
 retry:
 	ida_pre_get(&mnt_id_ida, GFP_KERNEL);
 	spin_lock(&vfsmount_lock);
-	res = ida_get_new(&mnt_id_ida, &mnt->mnt_id);
+	res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
+	if (!res)
+		mnt_id_start = mnt->mnt_id + 1;
 	spin_unlock(&vfsmount_lock);
 	if (res == -EAGAIN)
 		goto retry;
@@ -79,8 +83,11 @@ static int mnt_alloc_id(struct vfsmount *mnt)
 
 static void mnt_free_id(struct vfsmount *mnt)
 {
+	int id = mnt->mnt_id;
 	spin_lock(&vfsmount_lock);
-	ida_remove(&mnt_id_ida, mnt->mnt_id);
+	ida_remove(&mnt_id_ida, id);
+	if (mnt_id_start > id)
+		mnt_id_start = id;
 	spin_unlock(&vfsmount_lock);
 }
 
@@ -91,10 +98,18 @@ static void mnt_free_id(struct vfsmount *mnt)
  */
 static int mnt_alloc_group_id(struct vfsmount *mnt)
 {
+	int res;
+
 	if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
 		return -ENOMEM;
 
-	return ida_get_new_above(&mnt_group_ida, 1, &mnt->mnt_group_id);
+	res = ida_get_new_above(&mnt_group_ida,
+				mnt_group_start,
+				&mnt->mnt_group_id);
+	if (!res)
+		mnt_group_start = mnt->mnt_group_id + 1;
+
+	return res;
 }
 
 /*
@@ -102,7 +117,10 @@ static int mnt_alloc_group_id(struct vfsmount *mnt)
  */
 void mnt_release_group_id(struct vfsmount *mnt)
 {
-	ida_remove(&mnt_group_ida, mnt->mnt_group_id);
+	int id = mnt->mnt_group_id;
+	ida_remove(&mnt_group_ida, id);
+	if (mnt_group_start > id)
+		mnt_group_start = id;
 	mnt->mnt_group_id = 0;
 }
 

fs/super.c

@@ -620,7 +620,8 @@ int set_anon_super(struct super_block *s, void *data)
 		return -ENOMEM;
 	spin_lock(&unnamed_dev_lock);
 	error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);
-	unnamed_dev_start = dev + 1;
+	if (!error)
+		unnamed_dev_start = dev + 1;
 	spin_unlock(&unnamed_dev_lock);
 	if (error == -EAGAIN)
 		/* We raced and lost with another CPU. */
@@ -631,7 +632,8 @@ int set_anon_super(struct super_block *s, void *data)
 	if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
 		spin_lock(&unnamed_dev_lock);
 		ida_remove(&unnamed_dev_ida, dev);
-		unnamed_dev_start = dev;
+		if (unnamed_dev_start > dev)
+			unnamed_dev_start = dev;
 		spin_unlock(&unnamed_dev_lock);
 		return -EMFILE;
 	}