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, 2 insertions, 2 deletions

diff --git a/io_uring/notif.c b/io_uring/notif.c
index 8dfbb0bd8e4d..ee3a33510b3c 100644
--- a/io_uring/notif.c
+++ b/io_uring/notif.c
@@ -89,7 +89,7 @@ static int io_link_skb(struct sk_buff *skb, struct ubuf_info *uarg)
 
 	/* make sure all noifications can be finished in the same task_work */
 	if (unlikely(notif->ctx != prev_notif->ctx ||
-		     notif->task != prev_notif->task))
+		     notif->tctx != prev_notif->tctx))
 		return -EEXIST;
 
 	nd->head = prev_nd->head;
@@ -115,7 +115,7 @@ struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx)
 	notif->opcode = IORING_OP_NOP;
 	notif->flags = 0;
 	notif->file = NULL;
-	notif->task = current;
+	notif->tctx = current->io_uring;
 	io_get_task_refs(1);
 	notif->file_node = NULL;
 	notif->buf_node = NULL;