Commit 8110c1a6 authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring: add support for IORING_SETUP_CLAMP 



Some applications like to start small in terms of ring size, and then
ramp up as needed. This is a bit tricky to do currently, since we don't
advertise the max ring size.

This adds IORING_SETUP_CLAMP. If set, and the values for SQ or CQ ring
size exceed what we support, then clamp them at the max values instead
of returning -EINVAL. Since we return the chosen ring sizes after setup,
no further changes are needed on the application side. io_uring already
changes the ring sizes if the application doesn't ask for power-of-two
sizes, for example.

Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent c6ca97b3

fs/io_uring.c

+14 −3
Original line number Diff line number Diff line
@@ -6234,8 +6234,13 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p) 
	bool account_mem;

	int ret;



	if (!entries || entries > IORING_MAX_ENTRIES)

	if (!entries)

		return -EINVAL;

	if (entries > IORING_MAX_ENTRIES) {

		if (!(p->flags & IORING_SETUP_CLAMP))

			return -EINVAL;

		entries = IORING_MAX_ENTRIES;

	}



	/*

	 * Use twice as many entries for the CQ ring. It's possible for the
@@ -6252,8 +6257,13 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p) 
		 * to a power-of-two, if it isn't already. We do NOT impose

		 * any cq vs sq ring sizing.

		 */

		if (p->cq_entries < p->sq_entries || p->cq_entries > IORING_MAX_CQ_ENTRIES)

		if (p->cq_entries < p->sq_entries)

			return -EINVAL;

		if (p->cq_entries > IORING_MAX_CQ_ENTRIES) {

			if (!(p->flags & IORING_SETUP_CLAMP))

				return -EINVAL;

			p->cq_entries = IORING_MAX_CQ_ENTRIES;

		}

		p->cq_entries = roundup_pow_of_two(p->cq_entries);

	} else {

		p->cq_entries = 2 * p->sq_entries;
@@ -6345,7 +6355,8 @@ static long io_uring_setup(u32 entries, struct io_uring_params __user *params) 
	}



	if (p.flags & ~(IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL |

			IORING_SETUP_SQ_AFF | IORING_SETUP_CQSIZE))

			IORING_SETUP_SQ_AFF | IORING_SETUP_CQSIZE |

			IORING_SETUP_CLAMP))

		return -EINVAL;



	ret = io_uring_create(entries, &p);

include/uapi/linux/io_uring.h

+1 −0
Original line number Diff line number Diff line
@@ -61,6 +61,7 @@ struct io_uring_sqe { 
#define IORING_SETUP_SQPOLL	(1U << 1)	/* SQ poll thread */

#define IORING_SETUP_SQ_AFF	(1U << 2)	/* sq_thread_cpu is valid */

#define IORING_SETUP_CQSIZE	(1U << 3)	/* app defines CQ size */

#define IORING_SETUP_CLAMP	(1U << 4)	/* clamp SQ/CQ ring sizes */



enum {

	IORING_OP_NOP,

CRA Git | Maintained and supported by SUSTech CRA and CCSE