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io_uring/net: simplify zerocopy send user API

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Following user feedback, this patch simplifies zerocopy send API. One of
the main complaints is that the current API is difficult with the
userspace managing notification slots, and then send retries with error
handling make it even worse.

Instead of keeping notification slots change it to the per-request
notifications model, which posts both completion and notification CQEs
for each request when any data has been sent, and only one CQE if it
fails. All notification CQEs will have IORING_CQE_F_NOTIF set and
IORING_CQE_F_MORE in completion CQEs indicates whether to wait a
notification or not.

IOSQE_CQE_SKIP_SUCCESS is disallowed with zerocopy sends for now.

This is less flexible, but greatly simplifies the user API and also the
kernel implementation. We reuse notif helpers in this patch, but in the
future there won't be need for keeping two requests.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/95287640ab98fc9417370afb16e310677c63e6ce.1662027856.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov
2022-09-01 11:54:04 +01:00
committed by Jens Axboe
parent 57f332246a
commit b48c312be0
7 changed files with 47 additions and 76 deletions
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7
include/uapi/linux/io_uring.h
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@@ -71,8 +71,8 @@ struct io_uring_sqe {
__s32 splice_fd_in;
__u32 file_index;
struct {
__u16 notification_idx;
__u16 addr_len;
__u16 __pad3[1];
};
};
union {
@@ -205,7 +205,7 @@ enum io_uring_op {
IORING_OP_GETXATTR,
IORING_OP_SOCKET,
IORING_OP_URING_CMD,
IORING_OP_SENDZC_NOTIF,
IORING_OP_SEND_ZC,
/* this goes last, obviously */
IORING_OP_LAST,
@@ -326,10 +326,13 @@ struct io_uring_cqe {
* IORING_CQE_F_BUFFER If set, the upper 16 bits are the buffer ID
* IORING_CQE_F_MORE If set, parent SQE will generate more CQE entries
* IORING_CQE_F_SOCK_NONEMPTY If set, more data to read after socket recv
* IORING_CQE_F_NOTIF Set for notification CQEs. Can be used to distinct
* them from sends.
*/
#define IORING_CQE_F_BUFFER (1U << 0)
#define IORING_CQE_F_MORE (1U << 1)
#define IORING_CQE_F_SOCK_NONEMPTY (1U << 2)
#define IORING_CQE_F_NOTIF (1U << 3)
enum {
IORING_CQE_BUFFER_SHIFT = 16,