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, 1 insertions, 1 deletions

diff --git a/io_uring/waitid.c b/io_uring/waitid.c
index 9b7c23f96c47..daef5dd644f0 100644
--- a/io_uring/waitid.c
+++ b/io_uring/waitid.c
@@ -331,7 +331,7 @@ int io_waitid(struct io_kiocb *req, unsigned int issue_flags)
 	hlist_add_head(&req->hash_node, &ctx->waitid_list);
 
 	init_waitqueue_func_entry(&iwa->wo.child_wait, io_waitid_wait);
-	iwa->wo.child_wait.private = req->task;
+	iwa->wo.child_wait.private = req->tctx->task;
 	iw->head = &current->signal->wait_chldexit;
 	add_wait_queue(iw->head, &iwa->wo.child_wait);