Commit 7d3fd88d authored by Josh Triplett's avatar Josh Triplett Committed by Jens Axboe
Browse files

io_uring: Support calling io_uring_register with a registered ring fd 



Add a new flag IORING_REGISTER_USE_REGISTERED_RING (set via the high bit
of the opcode) to treat the fd as a registered index rather than a file
descriptor.

This makes it possible for a library to open an io_uring, register the
ring fd, close the ring fd, and subsequently use the ring entirely via
registered index.

Signed-off-by: default avatarJosh Triplett <josh@joshtriplett.org>
Link: https://lore.kernel.org/r/f2396369e638284586b069dbddffb8c992afba95.1676419314.git.josh@joshtriplett.org


[axboe: remove extra high bit clear]
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent fbe870a7

include/uapi/linux/io_uring.h

+5 −1
Original line number Diff line number Diff line
@@ -472,6 +472,7 @@ struct io_uring_params { 
#define IORING_FEAT_RSRC_TAGS		(1U << 10)

#define IORING_FEAT_CQE_SKIP		(1U << 11)

#define IORING_FEAT_LINKED_FILE		(1U << 12)

#define IORING_FEAT_REG_REG_RING	(1U << 13)



/*

 * io_uring_register(2) opcodes and arguments
@@ -519,7 +520,10 @@ enum { 
	IORING_REGISTER_FILE_ALLOC_RANGE	= 25,



	/* this goes last */

	IORING_REGISTER_LAST

	IORING_REGISTER_LAST,



	/* flag added to the opcode to use a registered ring fd */

	IORING_REGISTER_USE_REGISTERED_RING	= 1U << 31

};



/* io-wq worker categories */

io_uring/io_uring.c

+26 −7
Original line number Diff line number Diff line
@@ -3785,7 +3785,7 @@ static __cold int io_uring_create(unsigned entries, struct io_uring_params *p, 
			IORING_FEAT_POLL_32BITS | IORING_FEAT_SQPOLL_NONFIXED |

			IORING_FEAT_EXT_ARG | IORING_FEAT_NATIVE_WORKERS |

			IORING_FEAT_RSRC_TAGS | IORING_FEAT_CQE_SKIP |

			IORING_FEAT_LINKED_FILE;

			IORING_FEAT_LINKED_FILE | IORING_FEAT_REG_REG_RING;



	if (copy_to_user(params, p, sizeof(*p))) {

		ret = -EFAULT;
@@ -4306,17 +4306,36 @@ SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode, 
	struct io_ring_ctx *ctx;

	long ret = -EBADF;

	struct fd f;

	bool use_registered_ring;



	use_registered_ring = !!(opcode & IORING_REGISTER_USE_REGISTERED_RING);

	opcode &= ~IORING_REGISTER_USE_REGISTERED_RING;



	if (opcode >= IORING_REGISTER_LAST)

		return -EINVAL;



	if (use_registered_ring) {

		/*

		 * Ring fd has been registered via IORING_REGISTER_RING_FDS, we

		 * need only dereference our task private array to find it.

		 */

		struct io_uring_task *tctx = current->io_uring;



		if (unlikely(!tctx || fd >= IO_RINGFD_REG_MAX))

			return -EINVAL;

		fd = array_index_nospec(fd, IO_RINGFD_REG_MAX);

		f.file = tctx->registered_rings[fd];

		f.flags = 0;

		if (unlikely(!f.file))

			return -EBADF;

	} else {

		f = fdget(fd);

	if (!f.file)

		if (unlikely(!f.file))

			return -EBADF;



		ret = -EOPNOTSUPP;

		if (!io_is_uring_fops(f.file))

			goto out_fput;

	}



	ctx = f.file->private_data;