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io-wq: max_worker fixes 

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().

Fixes: 2e480058dd ("io-wq: provide a way to limit max number of workers")
Reported-by: Beld Zhang <beldzhang@gmail.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/11f90e6b49410b7d1a88f5d04fb8d95bb86b8cf3.1634671835.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-10-19 20:31:26 +01:00 committed by Jens Axboe
parent 14cfbb7a78
commit bc369921d6
1 changed files with 5 additions and 2 deletions
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7
fs/io-wq.c
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@ -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;
}
@ -1291,15 +1291,18 @@ 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;