[PATCH 5.13 079/151] io-wq: fix IO_WORKER_F_FIXED issue in create_io_worker()

Greg Kroah-Hartman
2021-08-16T13:25:52Z

From: Hao Xu <haoxu@linux.alibaba.com>

[ Upstream commit 47cae0c71f7a126903f930191e6e9f103674aca1 ]

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: 3d4e4face9c1 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/io-wq.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 2c8a9a394884..91b0d1fb90eb 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -130,7 +130,7 @@ 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)
@@ -249,18 +249,20 @@ 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);
}
}

@@ -283,7 +285,7 @@ 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;
@@ -291,12 +293,14 @@ 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);
@@ -642,7 +646,7 @@ 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;
@@ -683,7 +687,7 @@ 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);
--
2.30.2