linux-kernel - [PATCH] io_uring: iterate req cache backwards

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Message-Id: <df6e93383161cd3bdbe19fe816b761af0096c303.1580518665.git.asml.silence@gmail.com>
Date:   Sat,  1 Feb 2020 03:58:00 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] io_uring: iterate req cache backwards

Grab requests from cache-array from the end, so can get by only
free_reqs.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 fs/io_uring.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index fb5c5b3e23f4..73a6c6a4ec50 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -585,8 +585,7 @@ struct io_submit_state {
 	 * io_kiocb alloc cache
 	 */
 	void			*reqs[IO_IOPOLL_BATCH];
-	unsigned		int free_reqs;
-	unsigned		int cur_req;
+	unsigned int		free_reqs;
 
 	/*
 	 * File reference cache
@@ -1188,12 +1187,10 @@ static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
 			ret = 1;
 		}
 		state->free_reqs = ret - 1;
-		state->cur_req = 1;
-		req = state->reqs[0];
+		req = state->reqs[ret - 1];
 	} else {
-		req = state->reqs[state->cur_req];
 		state->free_reqs--;
-		state->cur_req++;
+		req = state->reqs[state->free_reqs];
 	}
 
 got_it:
@@ -4837,8 +4834,7 @@ static void io_submit_state_end(struct io_submit_state *state)
 	blk_finish_plug(&state->plug);
 	io_file_put(state);
 	if (state->free_reqs)
-		kmem_cache_free_bulk(req_cachep, state->free_reqs,
-					&state->reqs[state->cur_req]);
+		kmem_cache_free_bulk(req_cachep, state->free_reqs, state->reqs);
 }
 
 /*
-- 
2.24.0