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linux/io_uring/register.c
Jens Axboe 7cc2a6eadc io_uring: add IORING_REGISTER_COPY_BUFFERS method 
Buffers can get registered with io_uring, which allows to skip the
repeated pin_pages, unpin/unref pages for each O_DIRECT operation. This
reduces the overhead of O_DIRECT IO.

However, registrering buffers can take some time. Normally this isn't an
issue as it's done at initialization time (and hence less critical), but
for cases where rings can be created and destroyed as part of an IO
thread pool, registering the same buffers for multiple rings become a
more time sensitive proposition. As an example, let's say an application
has an IO memory pool of 500G. Initial registration takes:

Got 500 huge pages (each 1024MB)
Registered 500 pages in 409 msec

or about 0.4 seconds. If we go higher to 900 1GB huge pages being
registered:

Registered 900 pages in 738 msec

which is, as expected, a fully linear scaling.

Rather than have each ring pin/map/register the same buffer pool,
provide an io_uring_register(2) opcode to simply duplicate the buffers
that are registered with another ring. Adding the same 900GB of
registered buffers to the target ring can then be accomplished in:

Copied 900 pages in 17 usec

While timing differs a bit, this provides around a 25,000-40,000x
speedup for this use case.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-09-12 10:14:15 -06:00

618 lines
14 KiB
C
Raw Blame History

// SPDX-License-Identifier: GPL-2.0
/*
* Code related to the io_uring_register() syscall
*
* Copyright (C) 2023 Jens Axboe
*/
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/syscalls.h>
#include <linux/refcount.h>
#include <linux/bits.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/nospec.h>
#include <linux/compat.h>
#include <linux/io_uring.h>
#include <linux/io_uring_types.h>
#include "io_uring.h"
#include "opdef.h"
#include "tctx.h"
#include "rsrc.h"
#include "sqpoll.h"
#include "register.h"
#include "cancel.h"
#include "kbuf.h"
#include "napi.h"
#include "eventfd.h"
#define IORING_MAX_RESTRICTIONS (IORING_RESTRICTION_LAST + \
IORING_REGISTER_LAST + IORING_OP_LAST)
static __cold int io_probe(struct io_ring_ctx *ctx, void __user *arg,
unsigned nr_args)
{
struct io_uring_probe *p;
size_t size;
int i, ret;
if (nr_args > IORING_OP_LAST)
nr_args = IORING_OP_LAST;
size = struct_size(p, ops, nr_args);
p = kzalloc(size, GFP_KERNEL);
if (!p)
return -ENOMEM;
ret = -EFAULT;
if (copy_from_user(p, arg, size))
goto out;
ret = -EINVAL;
if (memchr_inv(p, 0, size))
goto out;
p->last_op = IORING_OP_LAST - 1;
for (i = 0; i < nr_args; i++) {
p->ops[i].op = i;
if (io_uring_op_supported(i))
p->ops[i].flags = IO_URING_OP_SUPPORTED;
}
p->ops_len = i;
ret = 0;
if (copy_to_user(arg, p, size))
ret = -EFAULT;
out:
kfree(p);
return ret;
}
int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id)
{
const struct cred *creds;
creds = xa_erase(&ctx->personalities, id);
if (creds) {
put_cred(creds);
return 0;
}
return -EINVAL;
}
static int io_register_personality(struct io_ring_ctx *ctx)
{
const struct cred *creds;
u32 id;
int ret;
creds = get_current_cred();
ret = xa_alloc_cyclic(&ctx->personalities, &id, (void *)creds,
XA_LIMIT(0, USHRT_MAX), &ctx->pers_next, GFP_KERNEL);
if (ret < 0) {
put_cred(creds);
return ret;
}
return id;
}
static __cold int io_register_restrictions(struct io_ring_ctx *ctx,
void __user *arg, unsigned int nr_args)
{
struct io_uring_restriction *res;
size_t size;
int i, ret;
/* Restrictions allowed only if rings started disabled */
if (!(ctx->flags & IORING_SETUP_R_DISABLED))
return -EBADFD;
/* We allow only a single restrictions registration */
if (ctx->restrictions.registered)
return -EBUSY;
if (!arg || nr_args > IORING_MAX_RESTRICTIONS)
return -EINVAL;
size = array_size(nr_args, sizeof(*res));
if (size == SIZE_MAX)
return -EOVERFLOW;
res = memdup_user(arg, size);
if (IS_ERR(res))
return PTR_ERR(res);
ret = 0;
for (i = 0; i < nr_args; i++) {
switch (res[i].opcode) {
case IORING_RESTRICTION_REGISTER_OP:
if (res[i].register_op >= IORING_REGISTER_LAST) {
ret = -EINVAL;
goto out;
}
__set_bit(res[i].register_op,
ctx->restrictions.register_op);
break;
case IORING_RESTRICTION_SQE_OP:
if (res[i].sqe_op >= IORING_OP_LAST) {
ret = -EINVAL;
goto out;
}
__set_bit(res[i].sqe_op, ctx->restrictions.sqe_op);
break;
case IORING_RESTRICTION_SQE_FLAGS_ALLOWED:
ctx->restrictions.sqe_flags_allowed = res[i].sqe_flags;
break;
case IORING_RESTRICTION_SQE_FLAGS_REQUIRED:
ctx->restrictions.sqe_flags_required = res[i].sqe_flags;
break;
default:
ret = -EINVAL;
goto out;
}
}
out:
/* Reset all restrictions if an error happened */
if (ret != 0)
memset(&ctx->restrictions, 0, sizeof(ctx->restrictions));
else
ctx->restrictions.registered = true;
kfree(res);
return ret;
}
static int io_register_enable_rings(struct io_ring_ctx *ctx)
{
if (!(ctx->flags & IORING_SETUP_R_DISABLED))
return -EBADFD;
if (ctx->flags & IORING_SETUP_SINGLE_ISSUER && !ctx->submitter_task) {
WRITE_ONCE(ctx->submitter_task, get_task_struct(current));
/*
* Lazy activation attempts would fail if it was polled before
* submitter_task is set.
*/
if (wq_has_sleeper(&ctx->poll_wq))
io_activate_pollwq(ctx);
}
if (ctx->restrictions.registered)
ctx->restricted = 1;
ctx->flags &= ~IORING_SETUP_R_DISABLED;
if (ctx->sq_data && wq_has_sleeper(&ctx->sq_data->wait))
wake_up(&ctx->sq_data->wait);
return 0;
}
static __cold int __io_register_iowq_aff(struct io_ring_ctx *ctx,
cpumask_var_t new_mask)
{
int ret;
if (!(ctx->flags & IORING_SETUP_SQPOLL)) {
ret = io_wq_cpu_affinity(current->io_uring, new_mask);
} else {
mutex_unlock(&ctx->uring_lock);
ret = io_sqpoll_wq_cpu_affinity(ctx, new_mask);
mutex_lock(&ctx->uring_lock);
}
return ret;
}
static __cold int io_register_iowq_aff(struct io_ring_ctx *ctx,
void __user *arg, unsigned len)
{
cpumask_var_t new_mask;
int ret;
if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
return -ENOMEM;
cpumask_clear(new_mask);
if (len > cpumask_size())
len = cpumask_size();
#ifdef CONFIG_COMPAT
if (in_compat_syscall())
ret = compat_get_bitmap(cpumask_bits(new_mask),
(const compat_ulong_t __user *)arg,
len * 8 /* CHAR_BIT */);
else
#endif
ret = copy_from_user(new_mask, arg, len);
if (ret) {
free_cpumask_var(new_mask);
return -EFAULT;
}
ret = __io_register_iowq_aff(ctx, new_mask);
free_cpumask_var(new_mask);
return ret;
}
static __cold int io_unregister_iowq_aff(struct io_ring_ctx *ctx)
{
return __io_register_iowq_aff(ctx, NULL);
}
static __cold int io_register_iowq_max_workers(struct io_ring_ctx *ctx,
void __user *arg)
__must_hold(&ctx->uring_lock)
{
struct io_tctx_node *node;
struct io_uring_task *tctx = NULL;
struct io_sq_data *sqd = NULL;
__u32 new_count[2];
int i, ret;
if (copy_from_user(new_count, arg, sizeof(new_count)))
return -EFAULT;
for (i = 0; i < ARRAY_SIZE(new_count); i++)
if (new_count[i] > INT_MAX)
return -EINVAL;
if (ctx->flags & IORING_SETUP_SQPOLL) {
sqd = ctx->sq_data;
if (sqd) {
/*
* Observe the correct sqd->lock -> ctx->uring_lock
* ordering. Fine to drop uring_lock here, we hold
* a ref to the ctx.
*/
refcount_inc(&sqd->refs);
mutex_unlock(&ctx->uring_lock);
mutex_lock(&sqd->lock);
mutex_lock(&ctx->uring_lock);
if (sqd->thread)
tctx = sqd->thread->io_uring;
}
} else {
tctx = current->io_uring;
}
BUILD_BUG_ON(sizeof(new_count) != sizeof(ctx->iowq_limits));
for (i = 0; i < ARRAY_SIZE(new_count); i++)
if (new_count[i])
ctx->iowq_limits[i] = new_count[i];
ctx->iowq_limits_set = true;
if (tctx && tctx->io_wq) {
ret = io_wq_max_workers(tctx->io_wq, new_count);
if (ret)
goto err;
} else {
memset(new_count, 0, sizeof(new_count));
}
if (sqd) {
mutex_unlock(&ctx->uring_lock);
mutex_unlock(&sqd->lock);
io_put_sq_data(sqd);
mutex_lock(&ctx->uring_lock);
}
if (copy_to_user(arg, new_count, sizeof(new_count)))
return -EFAULT;
/* that's it for SQPOLL, only the SQPOLL task creates requests */
if (sqd)
return 0;
/* now propagate the restriction to all registered users */
list_for_each_entry(node, &ctx->tctx_list, ctx_node) {
tctx = node->task->io_uring;
if (WARN_ON_ONCE(!tctx->io_wq))
continue;
for (i = 0; i < ARRAY_SIZE(new_count); i++)
new_count[i] = ctx->iowq_limits[i];
/* ignore errors, it always returns zero anyway */
(void)io_wq_max_workers(tctx->io_wq, new_count);
}
return 0;
err:
if (sqd) {
mutex_unlock(&ctx->uring_lock);
mutex_unlock(&sqd->lock);
io_put_sq_data(sqd);
mutex_lock(&ctx->uring_lock);
}
return ret;
}
static int io_register_clock(struct io_ring_ctx *ctx,
struct io_uring_clock_register __user *arg)
{
struct io_uring_clock_register reg;
if (copy_from_user(&reg, arg, sizeof(reg)))
return -EFAULT;
if (memchr_inv(&reg.__resv, 0, sizeof(reg.__resv)))
return -EINVAL;
switch (reg.clockid) {
case CLOCK_MONOTONIC:
ctx->clock_offset = 0;
break;
case CLOCK_BOOTTIME:
ctx->clock_offset = TK_OFFS_BOOT;
break;
default:
return -EINVAL;
}
ctx->clockid = reg.clockid;
return 0;
}
static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
void __user *arg, unsigned nr_args)
__releases(ctx->uring_lock)
__acquires(ctx->uring_lock)
{
int ret;
/*
* We don't quiesce the refs for register anymore and so it can't be
* dying as we're holding a file ref here.
*/
if (WARN_ON_ONCE(percpu_ref_is_dying(&ctx->refs)))
return -ENXIO;
if (ctx->submitter_task && ctx->submitter_task != current)
return -EEXIST;
if (ctx->restricted) {
opcode = array_index_nospec(opcode, IORING_REGISTER_LAST);
if (!test_bit(opcode, ctx->restrictions.register_op))
return -EACCES;
}
switch (opcode) {
case IORING_REGISTER_BUFFERS:
ret = -EFAULT;
if (!arg)
break;
ret = io_sqe_buffers_register(ctx, arg, nr_args, NULL);
break;
case IORING_UNREGISTER_BUFFERS:
ret = -EINVAL;
if (arg || nr_args)
break;
ret = io_sqe_buffers_unregister(ctx);
break;
case IORING_REGISTER_FILES:
ret = -EFAULT;
if (!arg)
break;
ret = io_sqe_files_register(ctx, arg, nr_args, NULL);
break;
case IORING_UNREGISTER_FILES:
ret = -EINVAL;
if (arg || nr_args)
break;
ret = io_sqe_files_unregister(ctx);
break;
case IORING_REGISTER_FILES_UPDATE:
ret = io_register_files_update(ctx, arg, nr_args);
break;
case IORING_REGISTER_EVENTFD:
ret = -EINVAL;
if (nr_args != 1)
break;
ret = io_eventfd_register(ctx, arg, 0);
break;
case IORING_REGISTER_EVENTFD_ASYNC:
ret = -EINVAL;
if (nr_args != 1)
break;
ret = io_eventfd_register(ctx, arg, 1);
break;
case IORING_UNREGISTER_EVENTFD:
ret = -EINVAL;
if (arg || nr_args)
break;
ret = io_eventfd_unregister(ctx);
break;
case IORING_REGISTER_PROBE:
ret = -EINVAL;
if (!arg || nr_args > 256)
break;
ret = io_probe(ctx, arg, nr_args);
break;
case IORING_REGISTER_PERSONALITY:
ret = -EINVAL;
if (arg || nr_args)
break;
ret = io_register_personality(ctx);
break;
case IORING_UNREGISTER_PERSONALITY:
ret = -EINVAL;
if (arg)
break;
ret = io_unregister_personality(ctx, nr_args);
break;
case IORING_REGISTER_ENABLE_RINGS:
ret = -EINVAL;
if (arg || nr_args)
break;
ret = io_register_enable_rings(ctx);
break;
case IORING_REGISTER_RESTRICTIONS:
ret = io_register_restrictions(ctx, arg, nr_args);
break;
case IORING_REGISTER_FILES2:
ret = io_register_rsrc(ctx, arg, nr_args, IORING_RSRC_FILE);
break;
case IORING_REGISTER_FILES_UPDATE2:
ret = io_register_rsrc_update(ctx, arg, nr_args,
IORING_RSRC_FILE);
break;
case IORING_REGISTER_BUFFERS2:
ret = io_register_rsrc(ctx, arg, nr_args, IORING_RSRC_BUFFER);
break;
case IORING_REGISTER_BUFFERS_UPDATE:
ret = io_register_rsrc_update(ctx, arg, nr_args,
IORING_RSRC_BUFFER);
break;
case IORING_REGISTER_IOWQ_AFF:
ret = -EINVAL;
if (!arg || !nr_args)
break;
ret = io_register_iowq_aff(ctx, arg, nr_args);
break;
case IORING_UNREGISTER_IOWQ_AFF:
ret = -EINVAL;
if (arg || nr_args)
break;
ret = io_unregister_iowq_aff(ctx);
break;
case IORING_REGISTER_IOWQ_MAX_WORKERS:
ret = -EINVAL;
if (!arg || nr_args != 2)
break;
ret = io_register_iowq_max_workers(ctx, arg);
break;
case IORING_REGISTER_RING_FDS:
ret = io_ringfd_register(ctx, arg, nr_args);
break;
case IORING_UNREGISTER_RING_FDS:
ret = io_ringfd_unregister(ctx, arg, nr_args);
break;
case IORING_REGISTER_PBUF_RING:
ret = -EINVAL;
if (!arg || nr_args != 1)
break;
ret = io_register_pbuf_ring(ctx, arg);
break;
case IORING_UNREGISTER_PBUF_RING:
ret = -EINVAL;
if (!arg || nr_args != 1)
break;
ret = io_unregister_pbuf_ring(ctx, arg);
break;
case IORING_REGISTER_SYNC_CANCEL:
ret = -EINVAL;
if (!arg || nr_args != 1)
break;
ret = io_sync_cancel(ctx, arg);
break;
case IORING_REGISTER_FILE_ALLOC_RANGE:
ret = -EINVAL;
if (!arg || nr_args)
break;
ret = io_register_file_alloc_range(ctx, arg);
break;
case IORING_REGISTER_PBUF_STATUS:
ret = -EINVAL;
if (!arg || nr_args != 1)
break;
ret = io_register_pbuf_status(ctx, arg);
break;
case IORING_REGISTER_NAPI:
ret = -EINVAL;
if (!arg || nr_args != 1)
break;
ret = io_register_napi(ctx, arg);
break;
case IORING_UNREGISTER_NAPI:
ret = -EINVAL;
if (nr_args != 1)
break;
ret = io_unregister_napi(ctx, arg);
break;
case IORING_REGISTER_CLOCK:
ret = -EINVAL;
if (!arg || nr_args)
break;
ret = io_register_clock(ctx, arg);
break;
case IORING_REGISTER_COPY_BUFFERS:
ret = -EINVAL;
if (!arg || nr_args != 1)
break;
ret = io_register_copy_buffers(ctx, arg);
break;
default:
ret = -EINVAL;
break;
}
return ret;
}
/*
* Given an 'fd' value, return the ctx associated with if. If 'registered' is
* true, then the registered index is used. Otherwise, the normal fd table.
* Caller must call fput() on the returned file, unless it's an ERR_PTR.
*/
struct file *io_uring_register_get_file(int fd, bool registered)
{
struct file *file;
if (registered) {
/*
* 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 ERR_PTR(-EINVAL);
fd = array_index_nospec(fd, IO_RINGFD_REG_MAX);
file = tctx->registered_rings[fd];
} else {
file = fget(fd);
}
if (unlikely(!file))
return ERR_PTR(-EBADF);
if (io_is_uring_fops(file))
return file;
fput(file);
return ERR_PTR(-EOPNOTSUPP);
}
SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode,
void __user *, arg, unsigned int, nr_args)
{
struct io_ring_ctx *ctx;
long ret = -EBADF;
struct file *file;
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;
file = io_uring_register_get_file(fd, use_registered_ring);
if (IS_ERR(file))
return PTR_ERR(file);
ctx = file->private_data;
mutex_lock(&ctx->uring_lock);
ret = __io_uring_register(ctx, opcode, arg, nr_args);
mutex_unlock(&ctx->uring_lock);
trace_io_uring_register(ctx, opcode, ctx->nr_user_files, ctx->nr_user_bufs, ret);
if (!use_registered_ring)
fput(file);
return ret;
}
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