Commit 47cae0c7 authored by Hao Xu's avatar Hao Xu Committed by Jens Axboe
Browse files

io-wq: fix IO_WORKER_F_FIXED issue in create_io_worker() 



There may be cases like:
        A                                 B
spin_lock(wqe->lock)
nr_workers is 0
nr_workers++
spin_unlock(wqe->lock)
                                     spin_lock(wqe->lock)
                                     nr_wokers is 1
                                     nr_workers++
                                     spin_unlock(wqe->lock)
create_io_worker()
  acct->worker is 1
                                     create_io_worker()
                                       acct->worker is 1

There should be one worker marked IO_WORKER_F_FIXED, but no one is.
Fix this by introduce a new agrument for create_io_worker() to indicate
if it is the first worker.

Fixes: 3d4e4fac ("io-wq: fix no lock protection of acct->nr_worker")
Signed-off-by: default avatarHao Xu <haoxu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20210808135434.68667-3-haoxu@linux.alibaba.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 49e7f0c7

fs/io-wq.c

+11 −7
Original line number Diff line number Diff line
@@ -129,7 +129,7 @@ struct io_cb_cancel_data { 
	bool cancel_all;

};



static void create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index);

static void create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index, bool first);

static void io_wqe_dec_running(struct io_worker *worker);



static bool io_worker_get(struct io_worker *worker)
@@ -248,18 +248,20 @@ static void io_wqe_wake_worker(struct io_wqe *wqe, struct io_wqe_acct *acct) 
	rcu_read_unlock();



	if (!ret) {

		bool do_create = false;

		bool do_create = false, first = false;



		raw_spin_lock_irq(&wqe->lock);

		if (acct->nr_workers < acct->max_workers) {

			atomic_inc(&acct->nr_running);

			atomic_inc(&wqe->wq->worker_refs);

			if (!acct->nr_workers)

				first = true;

			acct->nr_workers++;

			do_create = true;

		}

		raw_spin_unlock_irq(&wqe->lock);

		if (do_create)

			create_io_worker(wqe->wq, wqe, acct->index);

			create_io_worker(wqe->wq, wqe, acct->index, first);

	}

}
@@ -282,7 +284,7 @@ static void create_worker_cb(struct callback_head *cb) 
	struct io_wq *wq;

	struct io_wqe *wqe;

	struct io_wqe_acct *acct;

	bool do_create = false;

	bool do_create = false, first = false;



	cwd = container_of(cb, struct create_worker_data, work);

	wqe = cwd->wqe;
@@ -290,12 +292,14 @@ static void create_worker_cb(struct callback_head *cb) 
	acct = &wqe->acct[cwd->index];

	raw_spin_lock_irq(&wqe->lock);

	if (acct->nr_workers < acct->max_workers) {

		if (!acct->nr_workers)

			first = true;

		acct->nr_workers++;

		do_create = true;

	}

	raw_spin_unlock_irq(&wqe->lock);

	if (do_create) {

		create_io_worker(wq, cwd->wqe, cwd->index);

		create_io_worker(wq, wqe, cwd->index, first);

	} else {

		atomic_dec(&acct->nr_running);

		io_worker_ref_put(wq);
@@ -637,7 +641,7 @@ void io_wq_worker_sleeping(struct task_struct *tsk) 
	raw_spin_unlock_irq(&worker->wqe->lock);

}



static void create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index)

static void create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index, bool first)

{

	struct io_wqe_acct *acct = &wqe->acct[index];

	struct io_worker *worker;
@@ -678,7 +682,7 @@ static void create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index) 
	worker->flags |= IO_WORKER_F_FREE;

	if (index == IO_WQ_ACCT_BOUND)

		worker->flags |= IO_WORKER_F_BOUND;

	if ((acct->nr_workers == 1) && (worker->flags & IO_WORKER_F_BOUND))

	if (first && (worker->flags & IO_WORKER_F_BOUND))

		worker->flags |= IO_WORKER_F_FIXED;

	raw_spin_unlock_irq(&wqe->lock);

	wake_up_new_task(tsk);