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/rw.c b/io_uring/rw.c
index 144730344c0f..e368b9afde03 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -435,7 +435,7 @@ static bool io_rw_should_reissue(struct io_kiocb *req)
 	 * Play it safe and assume not safe to re-import and reissue if we're
 	 * not in the original thread group (or in task context).
 	 */
-	if (!same_thread_group(req->task, current) || !in_task())
+	if (!same_thread_group(req->tctx->task, current) || !in_task())
 		return false;
 	return true;
 }