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io_uring: carve io_poll_check_events fast path 

The fast path in io_poll_check_events() is when we have only one
(i.e. master) reference. Move all verification, cancellations
checks, edge case handling and so on under a common if.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/8c21c5d5e027e32dc553705e88796dec79ff6f93.1669821213.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2022-11-30 15:21:52 +00:00 committed by Jens Axboe
parent f6f7f903e7
commit 9805fa2d94
1 changed files with 22 additions and 19 deletions
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41
io_uring/poll.c
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@ -247,27 +247,30 @@ static int io_poll_check_events(struct io_kiocb *req, bool *locked)
do {
v = atomic_read(&req->poll_refs);
/* tw handler should be the owner, and so have some references */
if (WARN_ON_ONCE(!(v & IO_POLL_REF_MASK)))
return IOU_POLL_DONE;
if (v & IO_POLL_CANCEL_FLAG)
return -ECANCELED;
/*
* cqe.res contains only events of the first wake up
* and all others are be lost. Redo vfs_poll() to get
* up to date state.
*/
if ((v & IO_POLL_REF_MASK) != 1)
req->cqe.res = 0;
if (v & IO_POLL_RETRY_FLAG) {
req->cqe.res = 0;
if (unlikely(v != 1)) {
/* tw should be the owner and so have some refs */
if (WARN_ON_ONCE(!(v & IO_POLL_REF_MASK)))
return IOU_POLL_DONE;
if (v & IO_POLL_CANCEL_FLAG)
return -ECANCELED;
/*
* We won't find new events that came in between
* vfs_poll and the ref put unless we clear the flag
* in advance.
* cqe.res contains only events of the first wake up
* and all others are to be lost. Redo vfs_poll() to get
* up to date state.
*/
atomic_andnot(IO_POLL_RETRY_FLAG, &req->poll_refs);
v &= ~IO_POLL_RETRY_FLAG;
if ((v & IO_POLL_REF_MASK) != 1)
req->cqe.res = 0;
if (v & IO_POLL_RETRY_FLAG) {
req->cqe.res = 0;
/*
* We won't find new events that came in between
* vfs_poll and the ref put unless we clear the
* flag in advance.
*/
atomic_andnot(IO_POLL_RETRY_FLAG, &req->poll_refs);
v &= ~IO_POLL_RETRY_FLAG;
}
}
/* the mask was stashed in __io_poll_execute */