73 lines
2.1 KiB
Diff
73 lines
2.1 KiB
Diff
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Jens Axboe <axboe@kernel.dk>
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Date: Tue, 31 Aug 2021 13:53:00 -0600
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Subject: [PATCH] io-wq: fix queue stalling race
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We need to set the stalled bit early, before we drop the lock for adding
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us to the stall hash queue. If not, then we can race with new work being
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queued between adding us to the stall hash and io_worker_handle_work()
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marking us stalled.
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Signed-off-by: Jens Axboe <axboe@kernel.dk>
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[backport]
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Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
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---
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fs/io-wq.c | 15 +++++++--------
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1 file changed, 7 insertions(+), 8 deletions(-)
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diff --git a/fs/io-wq.c b/fs/io-wq.c
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index 6612d0aa497e..33678185f3bc 100644
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--- a/fs/io-wq.c
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+++ b/fs/io-wq.c
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@@ -437,8 +437,7 @@ static bool io_worker_can_run_work(struct io_worker *worker,
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}
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static struct io_wq_work *io_get_next_work(struct io_wqe *wqe,
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- struct io_worker *worker,
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- bool *stalled)
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+ struct io_worker *worker)
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__must_hold(wqe->lock)
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{
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struct io_wq_work_node *node, *prev;
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@@ -476,10 +475,14 @@ static struct io_wq_work *io_get_next_work(struct io_wqe *wqe,
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}
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if (stall_hash != -1U) {
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+ /*
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+ * Set this before dropping the lock to avoid racing with new
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+ * work being added and clearing the stalled bit.
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+ */
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+ wqe->flags |= IO_WQE_FLAG_STALLED;
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raw_spin_unlock(&wqe->lock);
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io_wait_on_hash(wqe, stall_hash);
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raw_spin_lock(&wqe->lock);
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- *stalled = true;
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}
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return NULL;
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@@ -519,7 +522,6 @@ static void io_worker_handle_work(struct io_worker *worker)
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do {
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struct io_wq_work *work;
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- bool stalled;
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get_next:
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/*
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* If we got some work, mark us as busy. If we didn't, but
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@@ -528,12 +530,9 @@ static void io_worker_handle_work(struct io_worker *worker)
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* can't make progress, any work completion or insertion will
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* clear the stalled flag.
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*/
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- stalled = false;
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- work = io_get_next_work(wqe, worker, &stalled);
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+ work = io_get_next_work(wqe, worker);
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if (work)
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__io_worker_busy(wqe, worker, work);
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- else if (stalled)
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- wqe->flags |= IO_WQE_FLAG_STALLED;
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raw_spin_unlock_irq(&wqe->lock);
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if (!work)
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--
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2.30.2
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