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io-wq: fix IO_WORKER_F_FIXED issue in create_io_worker()

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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: 3d4e4face9 ("io-wq: fix no lock protection of acct->nr_worker")
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20210808135434.68667-3-haoxu@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Hao Xu 2021-08-08 21:54:34 +08:00 committed by Jens Axboe
parent 49e7f0c789
commit 47cae0c71f
1 changed files with 11 additions and 7 deletions
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18
fs/io-wq.c
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@ -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 @@ fail:
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);