Commit 2a975d42 authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring/rw: don't allow multishot reads without NOWAIT support 



Supporting multishot reads requires support for NOWAIT, as the
alternative would be always having io-wq execute the work item whenever
the poll readiness triggered. Any fast file type will have NOWAIT
support (eg it understands both O_NONBLOCK and IOCB_NOWAIT). If the
given file type does not, then simply resort to single shot execution.

Cc: stable@vger.kernel.org
Fixes: fc68fcda ("io_uring/rw: add support for IORING_OP_READ_MULTISHOT")
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 39cd87c4

io_uring/rw.c

+8 −1
Original line number Diff line number Diff line
@@ -936,6 +936,13 @@ int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags) 


	ret = __io_read(req, issue_flags);



	/*

	 * If the file doesn't support proper NOWAIT, then disable multishot

	 * and stay in single shot mode.

	 */

	if (!io_file_supports_nowait(req))

		req->flags &= ~REQ_F_APOLL_MULTISHOT;



	/*

	 * If we get -EAGAIN, recycle our buffer and just let normal poll

	 * handling arm it.
@@ -955,7 +962,7 @@ int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags) 
	/*

	 * Any successful return value will keep the multishot read armed.

	 */

	if (ret > 0) {

	if (ret > 0 && req->flags & REQ_F_APOLL_MULTISHOT) {

		/*

		 * Put our buffer and post a CQE. If we fail to post a CQE, then

		 * jump to the termination path. This request is then done.