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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
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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)