io_uring/uring_cmd: avoid double indirect call in task work dispatch

io_uring task work dispatch makes an indirect call to struct io_kiocb's
io_task_work.func field to allow running arbitrary task work functions.
In the uring_cmd case, this calls io_uring_cmd_work(), which immediately
makes another indirect call to struct io_uring_cmd's task_work_cb field.
Change the uring_cmd task work callbacks to functions whose signatures
match io_req_tw_func_t. Add a function io_uring_cmd_from_tw() to convert
from the task work's struct io_tw_req argument to struct io_uring_cmd *.
Define a constant IO_URING_CMD_TASK_WORK_ISSUE_FLAGS to avoid
manufacturing issue_flags in the uring_cmd task work callbacks. Now
uring_cmd task work dispatch makes a single indirect call to the
uring_cmd implementation's callback. This also allows removing the
task_work_cb field from struct io_uring_cmd, freeing up 8 bytes for
future storage.
Since fuse_uring_send_in_task() now has access to the io_tw_token_t,
check its cancel field directly instead of relying on the
IO_URING_F_TASK_DEAD issue flag.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 2 insertions, 16 deletions

diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index c09b99e91c86..197474911f04 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -113,21 +113,8 @@ void io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
 }
 EXPORT_SYMBOL_GPL(io_uring_cmd_mark_cancelable);
 
-static void io_uring_cmd_work(struct io_tw_req tw_req, io_tw_token_t tw)
-{
-	struct io_kiocb *req = tw_req.req;
-	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
-	unsigned int flags = IO_URING_F_COMPLETE_DEFER;
-
-	if (unlikely(tw.cancel))
-		flags |= IO_URING_F_TASK_DEAD;
-
-	/* task_work executor checks the deffered list completion */
-	ioucmd->task_work_cb(ioucmd, flags);
-}
-
 void __io_uring_cmd_do_in_task(struct io_uring_cmd *ioucmd,
-			io_uring_cmd_tw_t task_work_cb,
+			io_req_tw_func_t task_work_cb,
 			unsigned flags)
 {
 	struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
@@ -135,8 +122,7 @@ void __io_uring_cmd_do_in_task(struct io_uring_cmd *ioucmd,
 	if (WARN_ON_ONCE(req->flags & REQ_F_APOLL_MULTISHOT))
 		return;
 
-	ioucmd->task_work_cb = task_work_cb;
-	req->io_task_work.func = io_uring_cmd_work;
+	req->io_task_work.func = task_work_cb;
 	__io_req_task_work_add(req, flags);
 }
 EXPORT_SYMBOL_GPL(__io_uring_cmd_do_in_task);