[PATCH 5/6] io-wq: add support for uncancellable work

Jens Axboe
2020-01-07T17:06:44Z

Not all work can be cancelled, some of it we may need to guarantee
that it runs to completion. Allow the caller to set IO_WQ_WORK_NO_CANCEL
on work that must not be cancelled. Note that the caller work function
must also check for IO_WQ_WORK_NO_CANCEL on work that is marked
IO_WQ_WORK_CANCEL.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
fs/io-wq.c | 8 +++++++-
fs/io-wq.h | 1 +
fs/io_uring.c | 5 ++++-
3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 541c8a3e0bbb..2f94170eeb89 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -452,6 +452,10 @@ static void io_worker_handle_work(struct io_worker *worker)
}
if (!worker->creds)
worker->creds = override_creds(wq->creds);
+ /*
+ * OK to set IO_WQ_WORK_CANCEL even for uncancellable work,
+ * the worker function will do the right thing.
+ */
if (test_bit(IO_WQ_BIT_CANCEL, &wq->state))
work->flags |= IO_WQ_WORK_CANCEL;
if (worker->mm)
@@ -824,6 +828,7 @@ static bool io_work_cancel(struct io_worker *worker, void *cancel_data)
*/
spin_lock_irqsave(&worker->lock, flags);
if (worker->cur_work &&
+ !(worker->cur_work->flags & IO_WQ_WORK_NO_CANCEL) &&
data->cancel(worker->cur_work, data->caller_data)) {
send_sig(SIGINT, worker->task, 1);
ret = true;
@@ -898,7 +903,8 @@ static bool io_wq_worker_cancel(struct io_worker *worker, void *data)
return false;

spin_lock_irqsave(&worker->lock, flags);
- if (worker->cur_work == work) {
+ if (worker->cur_work == work &&
+ !(worker->cur_work->flags & IO_WQ_WORK_NO_CANCEL)) {
send_sig(SIGINT, worker->task, 1);
ret = true;
}
diff --git a/fs/io-wq.h b/fs/io-wq.h
index 3f5e356de980..04d60ad38dfc 100644
--- a/fs/io-wq.h
+++ b/fs/io-wq.h
@@ -12,6 +12,7 @@ enum {
IO_WQ_WORK_UNBOUND = 32,
IO_WQ_WORK_INTERNAL = 64,
IO_WQ_WORK_CB = 128,
+ IO_WQ_WORK_NO_CANCEL = 256,

IO_WQ_HASH_SHIFT = 24, /* upper 8 bits are used for hash key */
};
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 53ff67ab5c4b..e12b1545468d 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3457,8 +3457,11 @@ static void io_wq_submit_work(struct io_wq_work **workptr)
struct io_kiocb *nxt = NULL;
int ret = 0;

- if (work->flags & IO_WQ_WORK_CANCEL)
+ /* if NO_CANCEL is set, we must still run the work */
+ if ((work->flags & (IO_WQ_WORK_CANCEL|IO_WQ_WORK_NO_CANCEL)) ==
+ IO_WQ_WORK_CANCEL) {
ret = -ECANCELED;
+ }

if (!ret) {
req->has_user = (work->flags & IO_WQ_WORK_HAS_MM) != 0;
--
2.24.1