[PATCH 6.8 106/172] io_uring: refactor DEFER_TASKRUN multishot checks

Greg Kroah-Hartman
2024-04-15T14:28:41Z

From: Pavel Begunkov <asml.silence@gmail.com>

Commit e0e4ab52d17096d96c21a6805ccd424b283c3c6d upstream.

We disallow DEFER_TASKRUN multishots from running by io-wq, which is
checked by individual opcodes in the issue path. We can consolidate all
it in io_wq_submit_work() at the same time moving the checks out of the
hot path.

Suggested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/e492f0f11588bb5aa11d7d24e6f53b7c7628afdb.1709905727.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
io_uring/io_uring.c | 20 ++++++++++++++++++++
io_uring/net.c | 21 ---------------------
io_uring/rw.c | 2 --
3 files changed, 20 insertions(+), 23 deletions(-)

--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -949,6 +949,8 @@ bool io_fill_cqe_req_aux(struct io_kiocb
u64 user_data = req->cqe.user_data;
struct io_uring_cqe *cqe;

+ lockdep_assert(!io_wq_current_is_worker());
+
if (!defer)
return __io_post_aux_cqe(ctx, user_data, res, cflags, false);

@@ -1950,6 +1952,24 @@ fail:
goto fail;
}

+ /*
+ * If DEFER_TASKRUN is set, it's only allowed to post CQEs from the
+ * submitter task context. Final request completions are handed to the
+ * right context, however this is not the case of auxiliary CQEs,
+ * which is the main mean of operation for multishot requests.
+ * Don't allow any multishot execution from io-wq. It's more restrictive
+ * than necessary and also cleaner.
+ */
+ if (req->flags & REQ_F_APOLL_MULTISHOT) {
+ err = -EBADFD;
+ if (!file_can_poll(req->file))
+ goto fail;
+ err = -ECANCELED;
+ if (io_arm_poll_handler(req, issue_flags) != IO_APOLL_OK)
+ goto fail;
+ return;
+ }
+
if (req->flags & REQ_F_FORCE_ASYNC) {
bool opcode_poll = def->pollin || def->pollout;

--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -78,19 +78,6 @@ struct io_sr_msg {
*/
#define MULTISHOT_MAX_RETRY 32

-static inline bool io_check_multishot(struct io_kiocb *req,
- unsigned int issue_flags)
-{
- /*
- * When ->locked_cq is set we only allow to post CQEs from the original
- * task context. Usual request completions will be handled in other
- * generic paths but multipoll may decide to post extra cqes.
- */
- return !(issue_flags & IO_URING_F_IOWQ) ||
- !(req->flags & REQ_F_APOLL_MULTISHOT) ||
- !req->ctx->task_complete;
-}
-
int io_shutdown_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
struct io_shutdown *shutdown = io_kiocb_to_cmd(req, struct io_shutdown);
@@ -837,9 +824,6 @@ int io_recvmsg(struct io_kiocb *req, uns
(sr->flags & IORING_RECVSEND_POLL_FIRST))
return io_setup_async_msg(req, kmsg, issue_flags);

- if (!io_check_multishot(req, issue_flags))
- return io_setup_async_msg(req, kmsg, issue_flags);
-
retry_multishot:
if (io_do_buffer_select(req)) {
void __user *buf;
@@ -935,9 +919,6 @@ int io_recv(struct io_kiocb *req, unsign
(sr->flags & IORING_RECVSEND_POLL_FIRST))
return -EAGAIN;

- if (!io_check_multishot(req, issue_flags))
- return -EAGAIN;
-
sock = sock_from_file(req->file);
if (unlikely(!sock))
return -ENOTSOCK;
@@ -1386,8 +1367,6 @@ int io_accept(struct io_kiocb *req, unsi
struct file *file;
int ret, fd;

- if (!io_check_multishot(req, issue_flags))
- return -EAGAIN;
retry:
if (!fixed) {
fd = __get_unused_fd_flags(accept->flags, accept->nofile);
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -932,8 +932,6 @@ int io_read_mshot(struct io_kiocb *req,
*/
if (!file_can_poll(req->file))
return -EBADFD;
- if (issue_flags & IO_URING_F_IOWQ)
- return -EAGAIN;

ret = __io_read(req, issue_flags);