linux-kernel - [PATCH v4 3/3] io_uring: Remove unnecessary BUILD_BUG

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Date:   Thu,  4 May 2023 05:18:56 -0700
From:   Breno Leitao <leitao@...ian.org>
To:     io-uring@...r.kernel.org, linux-nvme@...ts.infradead.org,
        asml.silence@...il.com, hch@....de, axboe@...nel.dk,
        ming.lei@...hat.com
Cc:     leit@...com, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, sagi@...mberg.me, joshi.k@...sung.com,
        kbusch@...nel.org
Subject: [PATCH v4 3/3] io_uring: Remove unnecessary BUILD_BUG_ON

In the io_uring_cmd_prep_async() there is an unnecessary compilation time
check to check if cmd is correctly placed at field 48 of the SQE.

This is unnecessary, since this check is already in place at
io_uring_init():

          BUILD_BUG_SQE_ELEM(48, __u64,  addr3);

Remove it and the uring_cmd_pdu_size() function, which is not used
anymore.

Keith started a discussion about this topic in the following thread:
Link: https://lore.kernel.org/lkml/ZDBmQOhbyU0iLhMw@kbusch-mbp.dhcp.thefacebook.com/

Signed-off-by: Breno Leitao <leitao@...ian.org>
Reviewed-by: Christoph Hellwig <hch@....de>
---
 io_uring/uring_cmd.c | 3 ---
 io_uring/uring_cmd.h | 8 --------
 2 files changed, 11 deletions(-)

diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index ed536d7499db..5e32db48696d 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -70,9 +70,6 @@ int io_uring_cmd_prep_async(struct io_kiocb *req)
 {
 	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
 
-	BUILD_BUG_ON(uring_cmd_pdu_size(0) != 16);
-	BUILD_BUG_ON(uring_cmd_pdu_size(1) != 80);
-
 	memcpy(req->async_data, ioucmd->sqe, uring_sqe_size(req->ctx));
 	ioucmd->sqe = req->async_data;
 	return 0;
diff --git a/io_uring/uring_cmd.h b/io_uring/uring_cmd.h
index 7c6697d13cb2..8117684ec3ca 100644
--- a/io_uring/uring_cmd.h
+++ b/io_uring/uring_cmd.h
@@ -3,11 +3,3 @@
 int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags);
 int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_uring_cmd_prep_async(struct io_kiocb *req);
-
-/*
- * The URING_CMD payload starts at 'cmd' in the first sqe, and continues into
- * the following sqe if SQE128 is used.
- */
-#define uring_cmd_pdu_size(is_sqe128)				\
-	((1 + !!(is_sqe128)) * sizeof(struct io_uring_sqe) -	\
-		offsetof(struct io_uring_sqe, cmd))
-- 
2.34.1