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io_uring: add IORING_OP_WAITID support

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This adds support for an async version of waitid(2), in a fully async
version. If an event isn't immediately available, wait for a callback
to trigger a retry.

The format of the sqe is as follows:

sqe->len		The 'which', the idtype being queried/waited for.
sqe->fd			The 'pid' (or id) being waited for.
sqe->file_index		The 'options' being set.
sqe->addr2		A pointer to siginfo_t, if any, being filled in.

buf_index, add3, and waitid_flags are reserved/unused for now.
waitid_flags will be used for options for this request type. One
interesting use case may be to add multi-shot support, so that the
request stays armed and posts a notification every time a monitored
process state change occurs.

Note that this does not support rusage, on Arnd's recommendation.

See the waitid(2) man page for details on the arguments.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2023-07-10 16:14:37 -06:00
parent 2e521a2064
commit f31ecf671d
8 changed files with 410 additions and 1 deletions
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2
include/linux/io_uring_types.h
View File

@ -313,6 +313,8 @@ struct io_ring_ctx {
struct list_head cq_overflow_list;
struct io_hash_table cancel_table;
struct hlist_head waitid_list;
const struct cred *sq_creds; /* cred used for __io_sq_thread() */
struct io_sq_data *sq_data; /* if using sq thread polling */

2
include/uapi/linux/io_uring.h
View File

@ -65,6 +65,7 @@ struct io_uring_sqe {
__u32 xattr_flags;
__u32 msg_ring_flags;
__u32 uring_cmd_flags;
__u32 waitid_flags;
};
__u64 user_data; /* data to be passed back at completion time */
/* pack this to avoid bogus arm OABI complaints */
@ -241,6 +242,7 @@ enum io_uring_op {
IORING_OP_SEND_ZC,
IORING_OP_SENDMSG_ZC,
IORING_OP_READ_MULTISHOT,
IORING_OP_WAITID,
/* this goes last, obviously */
IORING_OP_LAST,

3
io_uring/Makefile
View File

@ -7,5 +7,6 @@ obj-$(CONFIG_IO_URING) += io_uring.o xattr.o nop.o fs.o splice.o \
openclose.o uring_cmd.o epoll.o \
statx.o net.o msg_ring.o timeout.o \
sqpoll.o fdinfo.o tctx.o poll.o \
cancel.o kbuf.o rsrc.o rw.o opdef.o notif.o
cancel.o kbuf.o rsrc.o rw.o opdef.o \
notif.o waitid.o
obj-$(CONFIG_IO_WQ) += io-wq.o

5
io_uring/cancel.c
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@ -15,6 +15,7 @@
#include "tctx.h"
#include "poll.h"
#include "timeout.h"
#include "waitid.h"
#include "cancel.h"
struct io_cancel {
@ -119,6 +120,10 @@ int io_try_cancel(struct io_uring_task *tctx, struct io_cancel_data *cd,
if (ret != -ENOENT)
return ret;
ret = io_waitid_cancel(ctx, cd, issue_flags);
if (ret != -ENOENT)
return ret;
spin_lock(&ctx->completion_lock);
if (!(cd->flags & IORING_ASYNC_CANCEL_FD))
ret = io_timeout_cancel(ctx, cd);

3
io_uring/io_uring.c
View File

@ -92,6 +92,7 @@
#include "cancel.h"
#include "net.h"
#include "notif.h"
#include "waitid.h"
#include "timeout.h"
#include "poll.h"
@ -348,6 +349,7 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
INIT_LIST_HEAD(&ctx->tctx_list);
ctx->submit_state.free_list.next = NULL;
INIT_WQ_LIST(&ctx->locked_free_list);
INIT_HLIST_HEAD(&ctx->waitid_list);
INIT_DELAYED_WORK(&ctx->fallback_work, io_fallback_req_func);
INIT_WQ_LIST(&ctx->submit_state.compl_reqs);
return ctx;
@ -3303,6 +3305,7 @@ static __cold bool io_uring_try_cancel_requests(struct io_ring_ctx *ctx,
ret |= io_cancel_defer_files(ctx, task, cancel_all);
mutex_lock(&ctx->uring_lock);
ret |= io_poll_remove_all(ctx, task, cancel_all);
ret |= io_waitid_remove_all(ctx, task, cancel_all);
mutex_unlock(&ctx->uring_lock);
ret |= io_kill_timeouts(ctx, task, cancel_all);
if (task)

9
io_uring/opdef.c
View File

@ -33,6 +33,7 @@
#include "poll.h"
#include "cancel.h"
#include "rw.h"
#include "waitid.h"
static int io_no_issue(struct io_kiocb *req, unsigned int issue_flags)
{
@ -439,6 +440,10 @@ const struct io_issue_def io_issue_defs[] = {
.prep = io_read_mshot_prep,
.issue = io_read_mshot,
},
[IORING_OP_WAITID] = {
.prep = io_waitid_prep,
.issue = io_waitid,
},
};
const struct io_cold_def io_cold_defs[] = {
@ -661,6 +666,10 @@ const struct io_cold_def io_cold_defs[] = {
[IORING_OP_READ_MULTISHOT] = {
.name = "READ_MULTISHOT",
},
[IORING_OP_WAITID] = {
.name = "WAITID",
.async_size = sizeof(struct io_waitid_async),
},
};
const char *io_uring_get_opcode(u8 opcode)

372
io_uring/waitid.c Normal file
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@ -0,0 +1,372 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Support for async notification of waitid
*/
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/compat.h>
#include <linux/io_uring.h>
#include <uapi/linux/io_uring.h>
#include "io_uring.h"
#include "cancel.h"
#include "waitid.h"
#include "../kernel/exit.h"
static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state *ts);
#define IO_WAITID_CANCEL_FLAG BIT(31)
#define IO_WAITID_REF_MASK GENMASK(30, 0)
struct io_waitid {
struct file *file;
int which;
pid_t upid;
int options;
atomic_t refs;
struct wait_queue_head *head;
struct siginfo __user *infop;
struct waitid_info info;
};
static void io_waitid_free(struct io_kiocb *req)
{
struct io_waitid_async *iwa = req->async_data;
put_pid(iwa->wo.wo_pid);
kfree(req->async_data);
req->async_data = NULL;
req->flags &= ~REQ_F_ASYNC_DATA;
}
#ifdef CONFIG_COMPAT
static bool io_waitid_compat_copy_si(struct io_waitid *iw, int signo)
{
struct compat_siginfo __user *infop;
bool ret;
infop = (struct compat_siginfo __user *) iw->infop;
if (!user_write_access_begin(infop, sizeof(*infop)))
return false;
unsafe_put_user(signo, &infop->si_signo, Efault);
unsafe_put_user(0, &infop->si_errno, Efault);
unsafe_put_user(iw->info.cause, &infop->si_code, Efault);
unsafe_put_user(iw->info.pid, &infop->si_pid, Efault);
unsafe_put_user(iw->info.uid, &infop->si_uid, Efault);
unsafe_put_user(iw->info.status, &infop->si_status, Efault);
ret = true;
done:
user_write_access_end();
return ret;
Efault:
ret = false;
goto done;
}
#endif
static bool io_waitid_copy_si(struct io_kiocb *req, int signo)
{
struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
bool ret;
if (!iw->infop)
return true;
#ifdef CONFIG_COMPAT
if (req->ctx->compat)
return io_waitid_compat_copy_si(iw, signo);
#endif
if (!user_write_access_begin(iw->infop, sizeof(*iw->infop)))
return false;
unsafe_put_user(signo, &iw->infop->si_signo, Efault);
unsafe_put_user(0, &iw->infop->si_errno, Efault);
unsafe_put_user(iw->info.cause, &iw->infop->si_code, Efault);
unsafe_put_user(iw->info.pid, &iw->infop->si_pid, Efault);
unsafe_put_user(iw->info.uid, &iw->infop->si_uid, Efault);
unsafe_put_user(iw->info.status, &iw->infop->si_status, Efault);
ret = true;
done:
user_write_access_end();
return ret;
Efault:
ret = false;
goto done;
}
static int io_waitid_finish(struct io_kiocb *req, int ret)
{
int signo = 0;
if (ret > 0) {
signo = SIGCHLD;
ret = 0;
}
if (!io_waitid_copy_si(req, signo))
ret = -EFAULT;
io_waitid_free(req);
return ret;
}
static void io_waitid_complete(struct io_kiocb *req, int ret)
{
struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
struct io_tw_state ts = { .locked = true };
/* anyone completing better be holding a reference */
WARN_ON_ONCE(!(atomic_read(&iw->refs) & IO_WAITID_REF_MASK));
lockdep_assert_held(&req->ctx->uring_lock);
/*
* Did cancel find it meanwhile?
*/
if (hlist_unhashed(&req->hash_node))
return;
hlist_del_init(&req->hash_node);
ret = io_waitid_finish(req, ret);
if (ret < 0)
req_set_fail(req);
io_req_set_res(req, ret, 0);
io_req_task_complete(req, &ts);
}
static bool __io_waitid_cancel(struct io_ring_ctx *ctx, struct io_kiocb *req)
{
struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
struct io_waitid_async *iwa = req->async_data;
/*
* Mark us canceled regardless of ownership. This will prevent a
* potential retry from a spurious wakeup.
*/
atomic_or(IO_WAITID_CANCEL_FLAG, &iw->refs);
/* claim ownership */
if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)
return false;
spin_lock_irq(&iw->head->lock);
list_del_init(&iwa->wo.child_wait.entry);
spin_unlock_irq(&iw->head->lock);
io_waitid_complete(req, -ECANCELED);
return true;
}
int io_waitid_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
unsigned int issue_flags)
{
struct hlist_node *tmp;
struct io_kiocb *req;
int nr = 0;
if (cd->flags & (IORING_ASYNC_CANCEL_FD|IORING_ASYNC_CANCEL_FD_FIXED))
return -ENOENT;
io_ring_submit_lock(ctx, issue_flags);
hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) {
if (req->cqe.user_data != cd->data &&
!(cd->flags & IORING_ASYNC_CANCEL_ANY))
continue;
if (__io_waitid_cancel(ctx, req))
nr++;
if (!(cd->flags & IORING_ASYNC_CANCEL_ALL))
break;
}
io_ring_submit_unlock(ctx, issue_flags);
if (nr)
return nr;
return -ENOENT;
}
bool io_waitid_remove_all(struct io_ring_ctx *ctx, struct task_struct *task,
bool cancel_all)
{
struct hlist_node *tmp;
struct io_kiocb *req;
bool found = false;
lockdep_assert_held(&ctx->uring_lock);
hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) {
if (!io_match_task_safe(req, task, cancel_all))
continue;
__io_waitid_cancel(ctx, req);
found = true;
}
return found;
}
static inline bool io_waitid_drop_issue_ref(struct io_kiocb *req)
{
struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
struct io_waitid_async *iwa = req->async_data;
if (!atomic_sub_return(1, &iw->refs))
return false;
/*
* Wakeup triggered, racing with us. It was prevented from
* completing because of that, queue up the tw to do that.
*/
req->io_task_work.func = io_waitid_cb;
io_req_task_work_add(req);
remove_wait_queue(iw->head, &iwa->wo.child_wait);
return true;
}
static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state *ts)
{
struct io_waitid_async *iwa = req->async_data;
struct io_ring_ctx *ctx = req->ctx;
int ret;
io_tw_lock(ctx, ts);
ret = __do_wait(&iwa->wo);
/*
* If we get -ERESTARTSYS here, we need to re-arm and check again
* to ensure we get another callback. If the retry works, then we can
* just remove ourselves from the waitqueue again and finish the
* request.
*/
if (unlikely(ret == -ERESTARTSYS)) {
struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
/* Don't retry if cancel found it meanwhile */
ret = -ECANCELED;
if (!(atomic_read(&iw->refs) & IO_WAITID_CANCEL_FLAG)) {
iw->head = &current->signal->wait_chldexit;
add_wait_queue(iw->head, &iwa->wo.child_wait);
ret = __do_wait(&iwa->wo);
if (ret == -ERESTARTSYS) {
/* retry armed, drop our ref */
io_waitid_drop_issue_ref(req);
return;
}
remove_wait_queue(iw->head, &iwa->wo.child_wait);
}
}
io_waitid_complete(req, ret);
}
static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode,
int sync, void *key)
{
struct wait_opts *wo = container_of(wait, struct wait_opts, child_wait);
struct io_waitid_async *iwa = container_of(wo, struct io_waitid_async, wo);
struct io_kiocb *req = iwa->req;
struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
struct task_struct *p = key;
if (!pid_child_should_wake(wo, p))
return 0;
/* cancel is in progress */
if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)
return 1;
req->io_task_work.func = io_waitid_cb;
io_req_task_work_add(req);
list_del_init(&wait->entry);
return 1;
}
int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
if (sqe->addr || sqe->buf_index || sqe->addr3 || sqe->waitid_flags)
return -EINVAL;
iw->which = READ_ONCE(sqe->len);
iw->upid = READ_ONCE(sqe->fd);
iw->options = READ_ONCE(sqe->file_index);
iw->infop = u64_to_user_ptr(READ_ONCE(sqe->addr2));
return 0;
}
int io_waitid(struct io_kiocb *req, unsigned int issue_flags)
{
struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
struct io_ring_ctx *ctx = req->ctx;
struct io_waitid_async *iwa;
int ret;
if (io_alloc_async_data(req))
return -ENOMEM;
iwa = req->async_data;
iwa->req = req;
ret = kernel_waitid_prepare(&iwa->wo, iw->which, iw->upid, &iw->info,
iw->options, NULL);
if (ret)
goto done;
/*
* Mark the request as busy upfront, in case we're racing with the
* wakeup. If we are, then we'll notice when we drop this initial
* reference again after arming.
*/
atomic_set(&iw->refs, 1);
/*
* Cancel must hold the ctx lock, so there's no risk of cancelation
* finding us until a) we remain on the list, and b) the lock is
* dropped. We only need to worry about racing with the wakeup
* callback.
*/
io_ring_submit_lock(ctx, issue_flags);
hlist_add_head(&req->hash_node, &ctx->waitid_list);
init_waitqueue_func_entry(&iwa->wo.child_wait, io_waitid_wait);
iwa->wo.child_wait.private = req->task;
iw->head = &current->signal->wait_chldexit;
add_wait_queue(iw->head, &iwa->wo.child_wait);
ret = __do_wait(&iwa->wo);
if (ret == -ERESTARTSYS) {
/*
* Nobody else grabbed a reference, it'll complete when we get
* a waitqueue callback, or if someone cancels it.
*/
if (!io_waitid_drop_issue_ref(req)) {
io_ring_submit_unlock(ctx, issue_flags);
return IOU_ISSUE_SKIP_COMPLETE;
}
/*
* Wakeup triggered, racing with us. It was prevented from
* completing because of that, queue up the tw to do that.
*/
io_ring_submit_unlock(ctx, issue_flags);
return IOU_ISSUE_SKIP_COMPLETE;
}
hlist_del_init(&req->hash_node);
remove_wait_queue(iw->head, &iwa->wo.child_wait);
ret = io_waitid_finish(req, ret);
io_ring_submit_unlock(ctx, issue_flags);
done:
if (ret < 0)
req_set_fail(req);
io_req_set_res(req, ret, 0);
return IOU_OK;
}

15
io_uring/waitid.h Normal file
View File

@ -0,0 +1,15 @@
// SPDX-License-Identifier: GPL-2.0
#include "../kernel/exit.h"
struct io_waitid_async {
struct io_kiocb *req;
struct wait_opts wo;
};
int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
int io_waitid(struct io_kiocb *req, unsigned int issue_flags);
int io_waitid_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
unsigned int issue_flags);
bool io_waitid_remove_all(struct io_ring_ctx *ctx, struct task_struct *task,
bool cancel_all);