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io_uring: allow events and user_data update of running poll requests

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This adds two new POLL_ADD flags, IORING_POLL_UPDATE_EVENTS and
IORING_POLL_UPDATE_USER_DATA. As with the other POLL_ADD flag, these are
masked into sqe->len. If set, the POLL_ADD will have the following
behavior:

- sqe->addr must contain the the user_data of the poll request that
  needs to be modified. This field is otherwise invalid for a POLL_ADD
  command.

- If IORING_POLL_UPDATE_EVENTS is set, sqe->poll_events must contain the
  new mask for the existing poll request. There are no checks for whether
  these are identical or not, if a matching poll request is found, then it
  is re-armed with the new mask.

- If IORING_POLL_UPDATE_USER_DATA is set, sqe->off must contain the new
  user_data for the existing poll request.

A POLL_ADD with any of these flags set may complete with any of the
following results:

1) 0, which means that we successfully found the existing poll request
   specified, and performed the re-arm procedure. Any error from that
   re-arm will be exposed as a completion event for that original poll
   request, not for the update request.
2) -ENOENT, if no existing poll request was found with the given
   user_data.
3) -EALREADY, if the existing poll request was already in the process of
   being removed/canceled/completing.
4) -EACCES, if an attempt was made to modify an internal poll request
   (eg not one originally issued ass IORING_OP_POLL_ADD).

The usual -EINVAL cases apply as well, if any invalid fields are set
in the sqe for this command type.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-03-17 08:37:41 -06:00
parent b2cb805f6d
commit b69de288e9
2 changed files with 92 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

95
fs/io_uring.c
View file

@ -486,7 +486,15 @@ struct io_poll_iocb {
__poll_t events;
bool done;
bool canceled;
struct wait_queue_entry wait;
bool update_events;
bool update_user_data;
union {
struct wait_queue_entry wait;
struct {
u64 old_user_data;
u64 new_user_data;
};
};
};
struct io_poll_remove {
@ -4911,8 +4919,9 @@ static bool io_poll_complete(struct io_kiocb *req, __poll_t mask, int error)
}
if (!error)
error = mangle_poll(mask);
if (!__io_cqring_fill_event(req, error, flags) ||
(req->poll.events & EPOLLONESHOT)) {
if (req->poll.events & EPOLLONESHOT)
flags = 0;
if (!__io_cqring_fill_event(req, error, flags)) {
io_poll_remove_waitqs(req);
req->poll.done = true;
flags = 0;
@ -4992,6 +5001,7 @@ static void io_init_poll_iocb(struct io_poll_iocb *poll, __poll_t events,
poll->head = NULL;
poll->done = false;
poll->canceled = false;
poll->update_events = poll->update_user_data = false;
#define IO_POLL_UNMASK (EPOLLERR|EPOLLHUP|EPOLLNVAL|EPOLLRDHUP)
/* mask in events that we always want/need */
poll->events = events | IO_POLL_UNMASK;
@ -5370,24 +5380,36 @@ static int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
return -EINVAL;
if (sqe->addr || sqe->ioprio || sqe->off || sqe->buf_index)
if (sqe->ioprio || sqe->buf_index)
return -EINVAL;
flags = READ_ONCE(sqe->len);
if (flags & ~IORING_POLL_ADD_MULTI)
if (flags & ~(IORING_POLL_ADD_MULTI | IORING_POLL_UPDATE_EVENTS |
IORING_POLL_UPDATE_USER_DATA))
return -EINVAL;
events = READ_ONCE(sqe->poll32_events);
#ifdef __BIG_ENDIAN
events = swahw32(events);
#endif
if (!flags)
if (!(flags & IORING_POLL_ADD_MULTI))
events |= EPOLLONESHOT;
poll->update_events = poll->update_user_data = false;
if (flags & IORING_POLL_UPDATE_EVENTS) {
poll->update_events = true;
poll->old_user_data = READ_ONCE(sqe->addr);
}
if (flags & IORING_POLL_UPDATE_USER_DATA) {
poll->update_user_data = true;
poll->new_user_data = READ_ONCE(sqe->off);
}
if (!(poll->update_events || poll->update_user_data) &&
(sqe->off || sqe->addr))
return -EINVAL;
poll->events = demangle_poll(events) |
(events & (EPOLLEXCLUSIVE|EPOLLONESHOT));
return 0;
}
static int io_poll_add(struct io_kiocb *req, unsigned int issue_flags)
static int __io_poll_add(struct io_kiocb *req)
{
struct io_poll_iocb *poll = &req->poll;
struct io_ring_ctx *ctx = req->ctx;
@ -5413,6 +5435,63 @@ static int io_poll_add(struct io_kiocb *req, unsigned int issue_flags)
return ipt.error;
}
static int io_poll_update(struct io_kiocb *req)
{
struct io_ring_ctx *ctx = req->ctx;
struct io_kiocb *preq;
int ret;
spin_lock_irq(&ctx->completion_lock);
preq = io_poll_find(ctx, req->poll.old_user_data);
if (!preq) {
ret = -ENOENT;
goto err;
} else if (preq->opcode != IORING_OP_POLL_ADD) {
/* don't allow internal poll updates */
ret = -EACCES;
goto err;
}
if (!__io_poll_remove_one(preq, &preq->poll)) {
/* in process of completing/removal */
ret = -EALREADY;
goto err;
}
/* we now have a detached poll request. reissue. */
ret = 0;
err:
spin_unlock_irq(&ctx->completion_lock);
if (ret < 0) {
req_set_fail_links(req);
io_req_complete(req, ret);
return 0;
}
/* only mask one event flags, keep behavior flags */
if (req->poll.update_events) {
preq->poll.events &= ~0xffff;
preq->poll.events |= req->poll.events & 0xffff;
preq->poll.events |= IO_POLL_UNMASK;
}
if (req->poll.update_user_data)
preq->user_data = req->poll.new_user_data;
/* complete update request, we're done with it */
io_req_complete(req, ret);
ret = __io_poll_add(preq);
if (ret < 0) {
req_set_fail_links(preq);
io_req_complete(preq, ret);
}
return 0;
}
static int io_poll_add(struct io_kiocb *req, unsigned int issue_flags)
{
if (!req->poll.update_events && !req->poll.update_user_data)
return __io_poll_add(req);
return io_poll_update(req);
}
static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
{
struct io_timeout_data *data = container_of(timer,

5
include/uapi/linux/io_uring.h
View file

@ -166,8 +166,13 @@ enum {
* IORING_POLL_ADD_MULTI Multishot poll. Sets IORING_CQE_F_MORE if
* the poll handler will continue to report
* CQEs on behalf of the same SQE.
*
* IORING_POLL_UPDATE Update existing poll request, matching
* sqe->addr as the old user_data field.
*/
#define IORING_POLL_ADD_MULTI (1U << 0)
#define IORING_POLL_UPDATE_EVENTS (1U << 1)
#define IORING_POLL_UPDATE_USER_DATA (1U << 2)
/*
* IO completion data structure (Completion Queue Entry)