linux-stable/io_uring/tctx.c
Josh Triplett 6e76ac5958 io_uring: Add io_uring_setup flag to pre-register ring fd and never install it
With IORING_REGISTER_USE_REGISTERED_RING, an application can register
the ring fd and use it via registered index rather than installed fd.
This allows using a registered ring for everything *except* the initial
mmap.

With IORING_SETUP_NO_MMAP, io_uring_setup uses buffers allocated by the
user, rather than requiring a subsequent mmap.

The combination of the two allows a user to operate *entirely* via a
registered ring fd, making it unnecessary to ever install the fd in the
first place. So, add a flag IORING_SETUP_REGISTERED_FD_ONLY to make
io_uring_setup register the fd and return a registered index, without
installing the fd.

This allows an application to avoid touching the fd table at all, and
allows a library to never even momentarily install a file descriptor.

This splits out an io_ring_add_registered_file helper from
io_ring_add_registered_fd, for use by io_uring_setup.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Link: https://lore.kernel.org/r/bc8f431bada371c183b95a83399628b605e978a3.1682699803.git.josh@joshtriplett.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-05-16 08:06:00 -06:00

343 lines
7.4 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/nospec.h>
#include <linux/io_uring.h>
#include <uapi/linux/io_uring.h>
#include "io_uring.h"
#include "tctx.h"
static struct io_wq *io_init_wq_offload(struct io_ring_ctx *ctx,
struct task_struct *task)
{
struct io_wq_hash *hash;
struct io_wq_data data;
unsigned int concurrency;
mutex_lock(&ctx->uring_lock);
hash = ctx->hash_map;
if (!hash) {
hash = kzalloc(sizeof(*hash), GFP_KERNEL);
if (!hash) {
mutex_unlock(&ctx->uring_lock);
return ERR_PTR(-ENOMEM);
}
refcount_set(&hash->refs, 1);
init_waitqueue_head(&hash->wait);
ctx->hash_map = hash;
}
mutex_unlock(&ctx->uring_lock);
data.hash = hash;
data.task = task;
data.free_work = io_wq_free_work;
data.do_work = io_wq_submit_work;
/* Do QD, or 4 * CPUS, whatever is smallest */
concurrency = min(ctx->sq_entries, 4 * num_online_cpus());
return io_wq_create(concurrency, &data);
}
void __io_uring_free(struct task_struct *tsk)
{
struct io_uring_task *tctx = tsk->io_uring;
WARN_ON_ONCE(!xa_empty(&tctx->xa));
WARN_ON_ONCE(tctx->io_wq);
WARN_ON_ONCE(tctx->cached_refs);
percpu_counter_destroy(&tctx->inflight);
kfree(tctx);
tsk->io_uring = NULL;
}
__cold int io_uring_alloc_task_context(struct task_struct *task,
struct io_ring_ctx *ctx)
{
struct io_uring_task *tctx;
int ret;
tctx = kzalloc(sizeof(*tctx), GFP_KERNEL);
if (unlikely(!tctx))
return -ENOMEM;
ret = percpu_counter_init(&tctx->inflight, 0, GFP_KERNEL);
if (unlikely(ret)) {
kfree(tctx);
return ret;
}
tctx->io_wq = io_init_wq_offload(ctx, task);
if (IS_ERR(tctx->io_wq)) {
ret = PTR_ERR(tctx->io_wq);
percpu_counter_destroy(&tctx->inflight);
kfree(tctx);
return ret;
}
xa_init(&tctx->xa);
init_waitqueue_head(&tctx->wait);
atomic_set(&tctx->in_cancel, 0);
atomic_set(&tctx->inflight_tracked, 0);
task->io_uring = tctx;
init_llist_head(&tctx->task_list);
init_task_work(&tctx->task_work, tctx_task_work);
return 0;
}
int __io_uring_add_tctx_node(struct io_ring_ctx *ctx)
{
struct io_uring_task *tctx = current->io_uring;
struct io_tctx_node *node;
int ret;
if (unlikely(!tctx)) {
ret = io_uring_alloc_task_context(current, ctx);
if (unlikely(ret))
return ret;
tctx = current->io_uring;
if (ctx->iowq_limits_set) {
unsigned int limits[2] = { ctx->iowq_limits[0],
ctx->iowq_limits[1], };
ret = io_wq_max_workers(tctx->io_wq, limits);
if (ret)
return ret;
}
}
if (!xa_load(&tctx->xa, (unsigned long)ctx)) {
node = kmalloc(sizeof(*node), GFP_KERNEL);
if (!node)
return -ENOMEM;
node->ctx = ctx;
node->task = current;
ret = xa_err(xa_store(&tctx->xa, (unsigned long)ctx,
node, GFP_KERNEL));
if (ret) {
kfree(node);
return ret;
}
mutex_lock(&ctx->uring_lock);
list_add(&node->ctx_node, &ctx->tctx_list);
mutex_unlock(&ctx->uring_lock);
}
return 0;
}
int __io_uring_add_tctx_node_from_submit(struct io_ring_ctx *ctx)
{
int ret;
if (ctx->flags & IORING_SETUP_SINGLE_ISSUER
&& ctx->submitter_task != current)
return -EEXIST;
ret = __io_uring_add_tctx_node(ctx);
if (ret)
return ret;
current->io_uring->last = ctx;
return 0;
}
/*
* Remove this io_uring_file -> task mapping.
*/
__cold void io_uring_del_tctx_node(unsigned long index)
{
struct io_uring_task *tctx = current->io_uring;
struct io_tctx_node *node;
if (!tctx)
return;
node = xa_erase(&tctx->xa, index);
if (!node)
return;
WARN_ON_ONCE(current != node->task);
WARN_ON_ONCE(list_empty(&node->ctx_node));
mutex_lock(&node->ctx->uring_lock);
list_del(&node->ctx_node);
mutex_unlock(&node->ctx->uring_lock);
if (tctx->last == node->ctx)
tctx->last = NULL;
kfree(node);
}
__cold void io_uring_clean_tctx(struct io_uring_task *tctx)
{
struct io_wq *wq = tctx->io_wq;
struct io_tctx_node *node;
unsigned long index;
xa_for_each(&tctx->xa, index, node) {
io_uring_del_tctx_node(index);
cond_resched();
}
if (wq) {
/*
* Must be after io_uring_del_tctx_node() (removes nodes under
* uring_lock) to avoid race with io_uring_try_cancel_iowq().
*/
io_wq_put_and_exit(wq);
tctx->io_wq = NULL;
}
}
void io_uring_unreg_ringfd(void)
{
struct io_uring_task *tctx = current->io_uring;
int i;
for (i = 0; i < IO_RINGFD_REG_MAX; i++) {
if (tctx->registered_rings[i]) {
fput(tctx->registered_rings[i]);
tctx->registered_rings[i] = NULL;
}
}
}
int io_ring_add_registered_file(struct io_uring_task *tctx, struct file *file,
int start, int end)
{
int offset;
for (offset = start; offset < end; offset++) {
offset = array_index_nospec(offset, IO_RINGFD_REG_MAX);
if (tctx->registered_rings[offset])
continue;
tctx->registered_rings[offset] = file;
return offset;
}
return -EBUSY;
}
static int io_ring_add_registered_fd(struct io_uring_task *tctx, int fd,
int start, int end)
{
struct file *file;
int offset;
file = fget(fd);
if (!file) {
return -EBADF;
} else if (!io_is_uring_fops(file)) {
fput(file);
return -EOPNOTSUPP;
}
offset = io_ring_add_registered_file(tctx, file, start, end);
if (offset < 0)
fput(file);
return offset;
}
/*
* Register a ring fd to avoid fdget/fdput for each io_uring_enter()
* invocation. User passes in an array of struct io_uring_rsrc_update
* with ->data set to the ring_fd, and ->offset given for the desired
* index. If no index is desired, application may set ->offset == -1U
* and we'll find an available index. Returns number of entries
* successfully processed, or < 0 on error if none were processed.
*/
int io_ringfd_register(struct io_ring_ctx *ctx, void __user *__arg,
unsigned nr_args)
{
struct io_uring_rsrc_update __user *arg = __arg;
struct io_uring_rsrc_update reg;
struct io_uring_task *tctx;
int ret, i;
if (!nr_args || nr_args > IO_RINGFD_REG_MAX)
return -EINVAL;
mutex_unlock(&ctx->uring_lock);
ret = __io_uring_add_tctx_node(ctx);
mutex_lock(&ctx->uring_lock);
if (ret)
return ret;
tctx = current->io_uring;
for (i = 0; i < nr_args; i++) {
int start, end;
if (copy_from_user(&reg, &arg[i], sizeof(reg))) {
ret = -EFAULT;
break;
}
if (reg.resv) {
ret = -EINVAL;
break;
}
if (reg.offset == -1U) {
start = 0;
end = IO_RINGFD_REG_MAX;
} else {
if (reg.offset >= IO_RINGFD_REG_MAX) {
ret = -EINVAL;
break;
}
start = reg.offset;
end = start + 1;
}
ret = io_ring_add_registered_fd(tctx, reg.data, start, end);
if (ret < 0)
break;
reg.offset = ret;
if (copy_to_user(&arg[i], &reg, sizeof(reg))) {
fput(tctx->registered_rings[reg.offset]);
tctx->registered_rings[reg.offset] = NULL;
ret = -EFAULT;
break;
}
}
return i ? i : ret;
}
int io_ringfd_unregister(struct io_ring_ctx *ctx, void __user *__arg,
unsigned nr_args)
{
struct io_uring_rsrc_update __user *arg = __arg;
struct io_uring_task *tctx = current->io_uring;
struct io_uring_rsrc_update reg;
int ret = 0, i;
if (!nr_args || nr_args > IO_RINGFD_REG_MAX)
return -EINVAL;
if (!tctx)
return 0;
for (i = 0; i < nr_args; i++) {
if (copy_from_user(&reg, &arg[i], sizeof(reg))) {
ret = -EFAULT;
break;
}
if (reg.resv || reg.data || reg.offset >= IO_RINGFD_REG_MAX) {
ret = -EINVAL;
break;
}
reg.offset = array_index_nospec(reg.offset, IO_RINGFD_REG_MAX);
if (tctx->registered_rings[reg.offset]) {
fput(tctx->registered_rings[reg.offset]);
tctx->registered_rings[reg.offset] = NULL;
}
}
return i ? i : ret;
}