Re: [PATCHv6] io_uring: add support for IORING_SETUP_SQE_MIXED

[Nathan Chancellor <nathan@kernel.org>]

On Tue, Oct 21, 2025 at 04:02:28PM -0600, Jens Axboe wrote:
> 
> On Thu, 16 Oct 2025 11:09:38 -0700, Keith Busch wrote:
> > Normal rings support 64b SQEs for posting submissions, while certain
> > features require the ring to be configured with IORING_SETUP_SQE128, as
> > they need to convey more information per submission. This, in turn,
> > makes ALL the SQEs be 128b in size. This is somewhat wasteful and
> > inefficient, particularly when only certain SQEs need to be of the
> > bigger variant.
> > 
> > [...]
> 
> Applied, thanks!
> 
> [1/1] io_uring: add support for IORING_SETUP_SQE_MIXED
>       commit: 31dc41afdef21f264364288a30013b538c46152e

This needs a pretty obvious fix up as clang points out:

  io_uring/fdinfo.c:103:22: error: variable 'sqe' is uninitialized when used here [-Werror,-Wuninitialized]
    103 |                 opcode = READ_ONCE(sqe->opcode);
        |                                    ^~~

I would have sent a formal patch but since it is at the top, I figured
it would get squashed anyways.

Cheers,
Nathan

diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c
index d5aa64203de5..5b26b2a97e1b 100644
--- a/io_uring/fdinfo.c
+++ b/io_uring/fdinfo.c
@@ -100,8 +100,8 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
 		if (sq_idx > sq_mask)
 			continue;
 
-		opcode = READ_ONCE(sqe->opcode);
 		sqe = &ctx->sq_sqes[sq_idx << sq_shift];
+		opcode = READ_ONCE(sqe->opcode);
 		if (sq_shift) {
 			sqe128 = true;
 		} else if (io_issue_defs[opcode].is_128) {