io_uring: move struct io_kiocb from task_struct to io_uring_task

Rather than store the task_struct itself in struct io_kiocb, store
the io_uring specific task_struct. The life times are the same in terms
of io_uring, and this avoids doing some dereferences through the
task_struct. For the hot path of putting local task references, we can
deref req->tctx instead, which we'll need anyway in that function
regardless of whether it's local or remote references.

This is mostly straight forward, except the original task PF_EXITING
check needs a bit of tweaking. task_work is _always_ run from the
originating task, except in the fallback case, where it's run from a
kernel thread. Replace the potentially racy (in case of fallback work)
checks for req->task->flags with current->flags. It's either the still
the original task, in which case PF_EXITING will be sane, or it has
PF_KTHREAD set, in which case it's fallback work. Both cases should
prevent moving forward with the given request.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 6 insertions, 4 deletions

diff --git a/io_uring/timeout.c b/io_uring/timeout.c
index 18286cb53a69..5b12bd6a804c 100644
--- a/io_uring/timeout.c
+++ b/io_uring/timeout.c
@@ -300,16 +300,18 @@ static void io_req_task_link_timeout(struct io_kiocb *req, struct io_tw_state *t
 {
 	struct io_timeout *timeout = io_kiocb_to_cmd(req, struct io_timeout);
 	struct io_kiocb *prev = timeout->prev;
-	int ret = -ENOENT;
+	int ret;
 
 	if (prev) {
-		if (!(req->task->flags & PF_EXITING)) {
+		if (!io_should_terminate_tw()) {
 			struct io_cancel_data cd = {
 				.ctx		= req->ctx,
 				.data		= prev->cqe.user_data,
 			};
 
-			ret = io_try_cancel(req->task->io_uring, &cd, 0);
+			ret = io_try_cancel(req->tctx, &cd, 0);
+		} else {
+			ret = -ECANCELED;
 		}
 		io_req_set_res(req, ret ?: -ETIME, 0);
 		io_req_task_complete(req, ts);
@@ -643,7 +645,7 @@ static bool io_match_task(struct io_kiocb *head, struct io_uring_task *tctx,
 {
 	struct io_kiocb *req;
 
-	if (tctx && head->task->io_uring != tctx)
+	if (tctx && head->tctx != tctx)
 		return false;
 	if (cancel_all)
 		return true;