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io_uring: add support for IORING_SETUP_CLAMP

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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: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2019-12-28 15:39:54 -07:00
parent c6ca97b30c
commit 8110c1a621
2 changed files with 15 additions and 3 deletions
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17
fs/io_uring.c
View File

@ -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);

1
include/uapi/linux/io_uring.h
View File

@ -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,