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io_uring/cmd: allow multishot polled commands 

Some commands like timestamping in the next patch can make use of
multishot polling, i.e. REQ_F_APOLL_MULTISHOT. Add support for that,
which is condensed in a single helper called io_cmd_poll_multishot().

The user who wants to continue with a request in a multishot mode must
call the function, and only if it returns 0 the user is free to proceed.
Apart from normal terminal errors, it can also end up with -EIOCBQUEUED,
in which case the user must forward it to the core io_uring. It's
forbidden to use task work while the request is executing in a multishot
mode.

The API is not foolproof, hence it's not exported to modules nor exposed
in public headers.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/bcf97c31659662c72b69fc8fcdf2a88cfc16e430.1750065793.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
pull/1279/head
Pavel Begunkov 2025-06-16 10:46:27 +01:00 committed by Jens Axboe
parent 1621518892
commit b955754959
2 changed files with 26 additions and 0 deletions
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23
io_uring/uring_cmd.c
View File

@ -12,6 +12,7 @@
#include "alloc_cache.h"
#include "rsrc.h"
#include "uring_cmd.h"
#include "poll.h"
void io_cmd_cache_free(const void *entry)
{
@ -136,6 +137,9 @@ void __io_uring_cmd_do_in_task(struct io_uring_cmd *ioucmd,
{
struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
if (WARN_ON_ONCE(req->flags & REQ_F_APOLL_MULTISHOT))
return;
ioucmd->task_work_cb = task_work_cb;
req->io_task_work.func = io_uring_cmd_work;
__io_req_task_work_add(req, flags);
@ -158,6 +162,9 @@ void io_uring_cmd_done(struct io_uring_cmd *ioucmd, ssize_t ret, u64 res2,
{
struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
if (WARN_ON_ONCE(req->flags & REQ_F_APOLL_MULTISHOT))
return;
io_uring_cmd_del_cancelable(ioucmd, issue_flags);
if (ret < 0)
@ -305,3 +312,19 @@ void io_uring_cmd_issue_blocking(struct io_uring_cmd *ioucmd)
io_req_queue_iowq(req);
}
int io_cmd_poll_multishot(struct io_uring_cmd *cmd,
unsigned int issue_flags, __poll_t mask)
{
struct io_kiocb *req = cmd_to_io_kiocb(cmd);
int ret;
if (likely(req->flags & REQ_F_APOLL_MULTISHOT))
return 0;
req->flags |= REQ_F_APOLL_MULTISHOT;
mask &= ~EPOLLONESHOT;
ret = io_arm_apoll(req, issue_flags, mask);
return ret == IO_APOLL_OK ? -EIOCBQUEUED : -ECANCELED;
}

3
io_uring/uring_cmd.h
View File

@ -18,3 +18,6 @@ bool io_uring_try_cancel_uring_cmd(struct io_ring_ctx *ctx,
struct io_uring_task *tctx, bool cancel_all);
void io_cmd_cache_free(const void *entry);
int io_cmd_poll_multishot(struct io_uring_cmd *cmd,
unsigned int issue_flags, __poll_t mask);