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Commit ac90f249 authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring: expose single mmap capability 



After commit 75b28aff we can get by with just a single mmap to
map both the sq and cq ring. However, userspace doesn't know that.

Add a features variable to io_uring_params, and notify userspace
that the kernel has this ability. This can then be used in liburing
(or in applications directly) to avoid the second mmap.

Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 75b28aff

fs/io_uring.c

+2 −0
Original line number Original line Diff line number Diff line
@@ -3391,6 +3391,8 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p) 
	p->cq_off.ring_entries = offsetof(struct io_rings, cq_ring_entries);

	p->cq_off.ring_entries = offsetof(struct io_rings, cq_ring_entries);

	p->cq_off.overflow = offsetof(struct io_rings, cq_overflow);

	p->cq_off.overflow = offsetof(struct io_rings, cq_overflow);

	p->cq_off.cqes = offsetof(struct io_rings, cqes);

	p->cq_off.cqes = offsetof(struct io_rings, cqes);



	p->features = IORING_FEAT_SINGLE_MMAP;

	return ret;

	return ret;

err:

err:

	io_ring_ctx_wait_and_kill(ctx);

	io_ring_ctx_wait_and_kill(ctx);

include/uapi/linux/io_uring.h

+7 −1
Original line number Original line Diff line number Diff line
@@ -128,11 +128,17 @@ struct io_uring_params { 
	__u32 flags;

	__u32 flags;

	__u32 sq_thread_cpu;

	__u32 sq_thread_cpu;

	__u32 sq_thread_idle;

	__u32 sq_thread_idle;

	__u32 resv[5];

	__u32 features;

	__u32 resv[4];

	struct io_sqring_offsets sq_off;

	struct io_sqring_offsets sq_off;

	struct io_cqring_offsets cq_off;

	struct io_cqring_offsets cq_off;

};

};





/*

 * io_uring_params->features flags

 */

#define IORING_FEAT_SINGLE_MMAP		(1U << 0)



/*

/*

 * io_uring_register(2) opcodes and arguments

 * io_uring_register(2) opcodes and arguments

 */

 */