Commit 17d3aeb3 authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
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io_uring: refactor io_get_sqe() 



The line of io_get_sqe() evaluating @head consists of too many
operations including READ_ONCE(), it's not convenient for probing.
Refactor it also improving readability.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/866ad6e4ef4851c7c61f6b0e08dbd0a8d1abce84.1623709150.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 7f1129d2

fs/io_uring.c

+2 −2
Original line number Diff line number Diff line
@@ -6685,8 +6685,8 @@ static void io_commit_sqring(struct io_ring_ctx *ctx) 
 */

static const struct io_uring_sqe *io_get_sqe(struct io_ring_ctx *ctx)

{

	u32 *sq_array = ctx->sq_array;

	unsigned head, mask = ctx->sq_entries - 1;

	unsigned sq_idx = ctx->cached_sq_head++ & mask;



	/*

	 * The cached sq head (or cq tail) serves two purposes:
@@ -6696,7 +6696,7 @@ static const struct io_uring_sqe *io_get_sqe(struct io_ring_ctx *ctx) 
	 * 2) allows the kernel side to track the head on its own, even

	 *    though the application is the one updating it.

	 */

	head = READ_ONCE(sq_array[ctx->cached_sq_head++ & mask]);

	head = READ_ONCE(ctx->sq_array[sq_idx]);

	if (likely(head < ctx->sq_entries))

		return &ctx->sq_sqes[head];