[PATCH 3/6] io_uring/cancel: don't default to setting req->work.cancel_seq

[Jens Axboe <axboe@kernel.dk>]

Just leave it unset by default, avoiding dipping into the last
cacheline (which is otherwise untouched) for the fast path of using
poll to drive networked traffic. Add a flag that tells us if the
sequence is valid or not, and then we can defer actually assigning
the flag and sequence until someone runs cancelations.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 include/linux/io_uring_types.h |  3 +++
 io_uring/cancel.c              |  3 +--
 io_uring/cancel.h              | 10 ++++++++++
 io_uring/io_uring.c            |  1 -
 io_uring/poll.c                |  6 +-----
 5 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 7f06cee02b58..69a043ff8460 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -464,6 +464,7 @@ enum io_req_flags {
 	REQ_F_ISREG_BIT,
 	REQ_F_POLL_NO_LAZY_BIT,
 	REQ_F_CAN_POLL_BIT,
+	REQ_F_CANCEL_SEQ_BIT,
 
 	/* not a real bit, just to check we're not overflowing the space */
 	__REQ_F_LAST_BIT,
@@ -538,6 +539,8 @@ enum {
 	REQ_F_POLL_NO_LAZY	= IO_REQ_FLAG(REQ_F_POLL_NO_LAZY_BIT),
 	/* file is pollable */
 	REQ_F_CAN_POLL		= IO_REQ_FLAG(REQ_F_CAN_POLL_BIT),
+	/* cancel sequence is set and valid */
+	REQ_F_CANCEL_SEQ	= IO_REQ_FLAG(REQ_F_CANCEL_SEQ_BIT),
 };
 
 typedef void (*io_req_tw_func_t)(struct io_kiocb *req, struct io_tw_state *ts);
diff --git a/io_uring/cancel.c b/io_uring/cancel.c
index 8a8b07dfc444..acfcdd7f059a 100644
--- a/io_uring/cancel.c
+++ b/io_uring/cancel.c
@@ -58,9 +58,8 @@ bool io_cancel_req_match(struct io_kiocb *req, struct io_cancel_data *cd)
 		return false;
 	if (cd->flags & IORING_ASYNC_CANCEL_ALL) {
 check_seq:
-		if (cd->seq == req->work.cancel_seq)
+		if (io_cancel_match_sequence(req, cd->seq))
 			return false;
-		req->work.cancel_seq = cd->seq;
 	}
 
 	return true;
diff --git a/io_uring/cancel.h b/io_uring/cancel.h
index c0a8e7c520b6..76b32e65c03c 100644
--- a/io_uring/cancel.h
+++ b/io_uring/cancel.h
@@ -25,4 +25,14 @@ void init_hash_table(struct io_hash_table *table, unsigned size);
 int io_sync_cancel(struct io_ring_ctx *ctx, void __user *arg);
 bool io_cancel_req_match(struct io_kiocb *req, struct io_cancel_data *cd);
 
+static inline bool io_cancel_match_sequence(struct io_kiocb *req, int sequence)
+{
+	if ((req->flags & REQ_F_CANCEL_SEQ) && sequence == req->work.cancel_seq)
+		return true;
+
+	req->flags |= REQ_F_CANCEL_SEQ;
+	req->work.cancel_seq = sequence;
+	return false;
+}
+
 #endif
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index d0e06784926f..9b499864f10d 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -463,7 +463,6 @@ static void io_prep_async_work(struct io_kiocb *req)
 
 	req->work.list.next = NULL;
 	req->work.flags = 0;
-	req->work.cancel_seq = atomic_read(&ctx->cancel_seq);
 	if (req->flags & REQ_F_FORCE_ASYNC)
 		req->work.flags |= IO_WQ_WORK_CONCURRENT;
 
diff --git a/io_uring/poll.c b/io_uring/poll.c
index 4afec733fef6..3f3380dc5f68 100644
--- a/io_uring/poll.c
+++ b/io_uring/poll.c
@@ -588,10 +588,7 @@ static int __io_arm_poll_handler(struct io_kiocb *req,
 				 struct io_poll_table *ipt, __poll_t mask,
 				 unsigned issue_flags)
 {
-	struct io_ring_ctx *ctx = req->ctx;
-
 	INIT_HLIST_NODE(&req->hash_node);
-	req->work.cancel_seq = atomic_read(&ctx->cancel_seq);
 	io_init_poll_iocb(poll, mask);
 	poll->file = req->file;
 	req->apoll_events = poll->events;
@@ -818,9 +815,8 @@ static struct io_kiocb *io_poll_find(struct io_ring_ctx *ctx, bool poll_only,
 		if (poll_only && req->opcode != IORING_OP_POLL_ADD)
 			continue;
 		if (cd->flags & IORING_ASYNC_CANCEL_ALL) {
-			if (cd->seq == req->work.cancel_seq)
+			if (io_cancel_match_sequence(req, cd->seq))
 				continue;
-			req->work.cancel_seq = cd->seq;
 		}
 		*out_bucket = hb;
 		return req;
-- 
2.43.0