From 0242f6426ea78fbe3933b44f8c55ae93ec37f6cc Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 31 Aug 2021 13:53:00 -0600 Subject: io-wq: fix queue stalling race We need to set the stalled bit early, before we drop the lock for adding us to the stall hash queue. If not, then we can race with new work being queued between adding us to the stall hash and io_worker_handle_work() marking us stalled. Signed-off-by: Jens Axboe --- fs/io-wq.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/fs/io-wq.c b/fs/io-wq.c index a94060b72f84..aa9656eb832e 100644 --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -436,8 +436,7 @@ static bool io_worker_can_run_work(struct io_worker *worker, } static struct io_wq_work *io_get_next_work(struct io_wqe *wqe, - struct io_worker *worker, - bool *stalled) + struct io_worker *worker) __must_hold(wqe->lock) { struct io_wq_work_node *node, *prev; @@ -475,10 +474,14 @@ static struct io_wq_work *io_get_next_work(struct io_wqe *wqe, } if (stall_hash != -1U) { + /* + * Set this before dropping the lock to avoid racing with new + * work being added and clearing the stalled bit. + */ + wqe->flags |= IO_WQE_FLAG_STALLED; raw_spin_unlock(&wqe->lock); io_wait_on_hash(wqe, stall_hash); raw_spin_lock(&wqe->lock); - *stalled = true; } return NULL; @@ -518,7 +521,6 @@ static void io_worker_handle_work(struct io_worker *worker) do { struct io_wq_work *work; - bool stalled; get_next: /* * If we got some work, mark us as busy. If we didn't, but @@ -527,12 +529,9 @@ get_next: * can't make progress, any work completion or insertion will * clear the stalled flag. */ - stalled = false; - work = io_get_next_work(wqe, worker, &stalled); + work = io_get_next_work(wqe, worker); if (work) __io_worker_busy(wqe, worker, work); - else if (stalled) - wqe->flags |= IO_WQE_FLAG_STALLED; raw_spin_unlock(&wqe->lock); if (!work) -- cgit v1.2.3