fs: Convert namespace IDAs to new API

We don't need to keep track of the starting value; the IDA is efficient.
Signed-off-by: Matthew Wilcox <willy@infradead.org>

fs/namespace.c

@@ -61,9 +61,6 @@ __setup("mphash_entries=", set_mphash_entries);
 static u64 event;
 static DEFINE_IDA(mnt_id_ida);
 static DEFINE_IDA(mnt_group_ida);
-static DEFINE_SPINLOCK(mnt_id_lock);
-static int mnt_id_start = 0;
-static int mnt_group_start = 1;
 
 static struct hlist_head *mount_hashtable __read_mostly;
 static struct hlist_head *mountpoint_hashtable __read_mostly;
@@ -101,50 +98,30 @@ static inline struct hlist_head *mp_hash(struct dentry *dentry)
 
 static int mnt_alloc_id(struct mount *mnt)
 {
-	int res;
+	int res = ida_alloc(&mnt_id_ida, GFP_KERNEL);
 
-retry:
-	ida_pre_get(&mnt_id_ida, GFP_KERNEL);
-	spin_lock(&mnt_id_lock);
-	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(&mnt_id_lock);
-	if (res == -EAGAIN)
-		goto retry;
-
-	return res;
+	if (res < 0)
+		return res;
+	mnt->mnt_id = res;
+	return 0;
 }
 
 static void mnt_free_id(struct mount *mnt)
 {
-	int id = mnt->mnt_id;
-	spin_lock(&mnt_id_lock);
-	ida_remove(&mnt_id_ida, id);
-	if (mnt_id_start > id)
-		mnt_id_start = id;
-	spin_unlock(&mnt_id_lock);
+	ida_free(&mnt_id_ida, mnt->mnt_id);
 }
 
 /*
  * Allocate a new peer group ID
- *
- * mnt_group_ida is protected by namespace_sem
  */
 static int mnt_alloc_group_id(struct mount *mnt)
 {
-	int res;
+	int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL);
 
-	if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
-		return -ENOMEM;
-
-	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;
+	if (res < 0)
+		return res;
+	mnt->mnt_group_id = res;
+	return 0;
 }
 
 /*
@@ -152,10 +129,7 @@ static int mnt_alloc_group_id(struct mount *mnt)
  */
 void mnt_release_group_id(struct mount *mnt)
 {
-	int id = mnt->mnt_group_id;
-	ida_remove(&mnt_group_ida, id);
-	if (mnt_group_start > id)
-		mnt_group_start = id;
+	ida_free(&mnt_group_ida, mnt->mnt_group_id);
 	mnt->mnt_group_id = 0;
 }