[PATCH 3/9] io-wq: add infra data structure for fixed workers

[Hao Xu <haoxu.linux@xxxxxxxxx>]

From: Hao Xu <howeyxu@xxxxxxxxxxx>

Add data sttructure and basic initialization for fixed worker.

Signed-off-by: Hao Xu <howeyxu@xxxxxxxxxxx>
---
 fs/io-wq.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 87 insertions(+), 11 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 35ce622f77ba..ac8faf1f7a0a 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -26,6 +26,7 @@ enum {
 	IO_WORKER_F_RUNNING	= 2,	/* account as running */
 	IO_WORKER_F_FREE	= 4,	/* worker on free list */
 	IO_WORKER_F_BOUND	= 8,	/* is doing bounded work */
+	IO_WORKER_F_FIXED	= 16,	/* is a fixed worker */
 	IO_WORKER_F_EXIT	= 32,	/* worker is exiting */
 };
 
@@ -37,6 +38,61 @@ enum {
 	IO_ACCT_STALLED_BIT	= 0,	/* stalled on hash */
 };
 
+struct io_wqe_acct {
+	/*
+	 * union {
+	 *	1) for normal worker
+	 *	struct {
+	 *		unsigned nr_workers;
+	 *		unsigned max_workers;
+	 *		struct io_wq_work_list work_list;
+	 *	};
+	 *	2) for fixed worker
+	 *	struct {
+	 *		unsigned nr_workers; // not meaningful
+	 *		unsigned max_workers; // not meaningful
+	 *		unsigned nr_fixed;
+	 *		unsigned max_works;
+	 *		struct io_worker **fixed_workers;
+	 *	};
+	 *	3) for fixed worker's private acct
+	 *	struct {
+	 *		unsigned nr_works;
+	 *		unsigned max_works;
+	 *		struct io_wq_work_list work_list;
+	 *	};
+	 *};
+	 */
+	union {
+		unsigned nr_workers;
+		unsigned nr_works;
+	};
+	unsigned max_workers;
+	unsigned nr_fixed;
+	unsigned max_works;
+	union {
+		struct io_wq_work_list work_list;
+		struct io_worker **fixed_workers;
+	};
+	/*
+	 * nr_running is not meaningful for fixed worker
+	 * but still keep the same logic for it for the
+	 * convinence for now. So do nr_workers and
+	 * max_workers.
+	 */
+	atomic_t nr_running;
+	/*
+	 * For 1), it protects the work_list, the other two member nr_workers
+	 * and max_workers are protected by wqe->lock.
+	 * For 2), it protects nr_fixed, max_works, fixed_workers
+	 * For 3), it protects nr_works, max_works and work_list.
+	 */
+	raw_spinlock_t lock;
+	int index;
+	unsigned long flags;
+	bool fixed_worker_registered;
+};
+
 /*
  * One for each thread in a wqe pool
  */
@@ -62,6 +118,8 @@ struct io_worker {
 		struct rcu_head rcu;
 		struct work_struct work;
 	};
+	int index;
+	struct io_wqe_acct acct;
 };
 
 #if BITS_PER_LONG == 64
@@ -72,16 +130,6 @@ struct io_worker {
 
 #define IO_WQ_NR_HASH_BUCKETS	(1u << IO_WQ_HASH_ORDER)
 
-struct io_wqe_acct {
-	unsigned nr_workers;
-	unsigned max_workers;
-	int index;
-	atomic_t nr_running;
-	raw_spinlock_t lock;
-	struct io_wq_work_list work_list;
-	unsigned long flags;
-};
-
 enum {
 	IO_WQ_ACCT_BOUND,
 	IO_WQ_ACCT_UNBOUND,
@@ -94,6 +142,7 @@ enum {
 struct io_wqe {
 	raw_spinlock_t lock;
 	struct io_wqe_acct acct[IO_WQ_ACCT_NR];
+	struct io_wqe_acct fixed_acct[IO_WQ_ACCT_NR];
 
 	int node;
 
@@ -1205,6 +1254,31 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 			atomic_set(&acct->nr_running, 0);
 			INIT_WQ_LIST(&acct->work_list);
 			raw_spin_lock_init(&acct->lock);
+
+			acct = &wqe->fixed_acct[i];
+			acct->index = i;
+			INIT_WQ_LIST(&acct->work_list);
+			raw_spin_lock_init(&acct->lock);
+			/*
+			 * nr_running for a fixed worker is meaningless
+			 * for now, init it to 1 to wround around the
+			 * io_wqe_dec_running logic
+			 */
+			atomic_set(&acct->nr_running, 1);
+			/*
+			 * max_workers for a fixed worker is meaningless
+			 * for now, init it so since number of fixed workers
+			 * should be controlled by users.
+			 */
+			acct->max_workers = task_rlimit(current, RLIMIT_NPROC);
+			raw_spin_lock_init(&acct->lock);
+			/*
+			 * For fixed worker, not necessary
+			 * but do it explicitly for clearity
+			 */
+			acct->nr_fixed = 0;
+			acct->max_works = 0;
+			acct->fixed_workers = NULL;
 		}
 		wqe->wq = wq;
 		raw_spin_lock_init(&wqe->lock);
@@ -1287,7 +1361,7 @@ static void io_wq_exit_workers(struct io_wq *wq)
 
 static void io_wq_destroy(struct io_wq *wq)
 {
-	int node;
+	int i, node;
 
 	cpuhp_state_remove_instance_nocalls(io_wq_online, &wq->cpuhp_node);
 
@@ -1299,6 +1373,8 @@ static void io_wq_destroy(struct io_wq *wq)
 		};
 		io_wqe_cancel_pending_work(wqe, &match);
 		free_cpumask_var(wqe->cpu_mask);
+		for (i = 0; i < IO_WQ_ACCT_NR; i++)
+			kfree(wqe->fixed_acct[i].fixed_workers);
 		kfree(wqe);
 	}
 	io_wq_put_hash(wq->hash);
-- 
2.36.0