On 10/19/21 20:31, Pavel Begunkov wrote:
First, fix nr_workers checks against max_workers, with max_worker registration, it may pretty easily happen that nr_workers > max_workers. Also, synchronise writing to acct->max_worker with wqe->lock. It's not an actual problem, but as we don't care about io_wqe_create_worker(), it's better than WRITE_ONCE()/READ_ONCE().
Jens, can you add Reported-by: Beld Zhang <beldzhang@xxxxxxxxx>
Fixes: 2e480058ddc2 ("io-wq: provide a way to limit max number of workers") Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx> --- fs/io-wq.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/io-wq.c b/fs/io-wq.c index 811299ac9684..cdf1719f6be6 100644 --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -253,7 +253,7 @@ static bool io_wqe_create_worker(struct io_wqe *wqe, struct io_wqe_acct *acct) pr_warn_once("io-wq is not configured for unbound workers");raw_spin_lock(&wqe->lock);- if (acct->nr_workers == acct->max_workers) { + if (acct->nr_workers >= acct->max_workers) { raw_spin_unlock(&wqe->lock); return true; } @@ -1290,15 +1290,18 @@ int io_wq_max_workers(struct io_wq *wq, int *new_count)rcu_read_lock();for_each_node(node) { + struct io_wqe *wqe = wq->wqes[node]; struct io_wqe_acct *acct;+ raw_spin_lock(&wqe->lock);for (i = 0; i < IO_WQ_ACCT_NR; i++) { - acct = &wq->wqes[node]->acct[i]; + acct = &wqe->acct[i]; prev = max_t(int, acct->max_workers, prev); if (new_count[i]) acct->max_workers = new_count[i]; new_count[i] = prev; } + raw_spin_unlock(&wqe->lock); } rcu_read_unlock(); return 0;
-- Pavel Begunkov
