[PATCHv6] io_uring: add support for IORING_SETUP_SQE_MIXED

[PATCHv6] io_uring: add support for IORING_SETUP_SQE_MIXED

[Keith Busch]

From: Keith Busch <kbusch@kernel.org>

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.

This adds support for setting up a ring with mixed SQE sizes, using
IORING_SETUP_SQE_MIXED. When setup in this mode, SQEs posted to the ring
may be either 64b or 128b in size. If a SQE is 128b in size, then opcode
will be set to a variante to indicate that this is the case. Any other
non-128b opcode will assume the SQ's default size.

SQEs on these types of mixed rings may also utilize NOP with skip
success set.  This can happen if the ring is one (small) SQE entry away
from wrapping, and an attempt is made to get a 128b SQE. As SQEs must be
contiguous in the SQ ring, a 128b SQE cannot wrap the ring. For this
case, a single NOP SQE should be inserted with the SKIP_SUCCESS flag
set. The kernel will process this as a normal NOP and without posting a
CQE.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
Changes from v5:

  - Incremenet the task context's cached_refs to account for using two
    entries (Caleb)

 include/uapi/linux/io_uring.h |  8 ++++++++
 io_uring/fdinfo.c             | 34 +++++++++++++++++++++++++-------
 io_uring/io_uring.c           | 37 +++++++++++++++++++++++++++++++----
 io_uring/io_uring.h           | 14 ++-----------
 io_uring/opdef.c              | 26 ++++++++++++++++++++++++
 io_uring/opdef.h              |  2 ++
 io_uring/register.c           |  2 +-
 io_uring/uring_cmd.c          | 17 ++++++++++++++--
 8 files changed, 114 insertions(+), 26 deletions(-)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 263bed13473ef..04797a9b76bc2 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -231,6 +231,12 @@ enum io_uring_sqe_flags_bit {
  */
 #define IORING_SETUP_CQE_MIXED		(1U << 18)
 
+/*
+ * Allow both 64b and 128b SQEs. If a 128b SQE is posted, it will have
+ * a 128b opcode.
+ */
+#define IORING_SETUP_SQE_MIXED		(1U << 19)
+
 enum io_uring_op {
 	IORING_OP_NOP,
 	IORING_OP_READV,
@@ -295,6 +301,8 @@ enum io_uring_op {
 	IORING_OP_READV_FIXED,
 	IORING_OP_WRITEV_FIXED,
 	IORING_OP_PIPE,
+	IORING_OP_NOP128,
+	IORING_OP_URING_CMD128,
 
 	/* this goes last, obviously */
 	IORING_OP_LAST,
diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c
index ff3364531c77b..d14d2e983b623 100644
--- a/io_uring/fdinfo.c
+++ b/io_uring/fdinfo.c
@@ -14,6 +14,7 @@
 #include "fdinfo.h"
 #include "cancel.h"
 #include "rsrc.h"
+#include "opdef.h"
 
 #ifdef CONFIG_NET_RX_BUSY_POLL
 static __cold void common_tracking_show_fdinfo(struct io_ring_ctx *ctx,
@@ -66,7 +67,6 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
 	unsigned int cq_head = READ_ONCE(r->cq.head);
 	unsigned int cq_tail = READ_ONCE(r->cq.tail);
 	unsigned int sq_shift = 0;
-	unsigned int sq_entries;
 	int sq_pid = -1, sq_cpu = -1;
 	u64 sq_total_time = 0, sq_work_time = 0;
 	unsigned int i;
@@ -89,26 +89,45 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
 	seq_printf(m, "CqTail:\t%u\n", cq_tail);
 	seq_printf(m, "CachedCqTail:\t%u\n", data_race(ctx->cached_cq_tail));
 	seq_printf(m, "SQEs:\t%u\n", sq_tail - sq_head);
-	sq_entries = min(sq_tail - sq_head, ctx->sq_entries);
-	for (i = 0; i < sq_entries; i++) {
-		unsigned int entry = i + sq_head;
+	while (sq_head < sq_tail) {
 		struct io_uring_sqe *sqe;
 		unsigned int sq_idx;
+		bool sqe128 = false;
+		u8 opcode;
 
 		if (ctx->flags & IORING_SETUP_NO_SQARRAY)
 			break;
-		sq_idx = READ_ONCE(ctx->sq_array[entry & sq_mask]);
+		sq_idx = READ_ONCE(ctx->sq_array[sq_head & sq_mask]);
 		if (sq_idx > sq_mask)
 			continue;
+
+		opcode = READ_ONCE(sqe->opcode);
 		sqe = &ctx->sq_sqes[sq_idx << sq_shift];
+		if (sq_shift)
+			sqe128 = true;
+		else if (io_issue_defs[opcode].is_128) {
+			if (!(ctx->flags & IORING_SETUP_SQE_MIXED)) {
+				seq_printf(m,
+					"%5u: invalid sqe, 128B entry on non-mixed sq\n",
+					sq_idx);
+				break;
+			}
+			if ((++sq_head & sq_mask) == 0) {
+				seq_printf(m,
+					"%5u: corrupted sqe, wrapping 128B entry\n",
+					sq_idx);
+				break;
+			}
+			sqe128 = true;
+		}
 		seq_printf(m, "%5u: opcode:%s, fd:%d, flags:%x, off:%llu, "
 			      "addr:0x%llx, rw_flags:0x%x, buf_index:%d "
 			      "user_data:%llu",
-			   sq_idx, io_uring_get_opcode(sqe->opcode), sqe->fd,
+			   sq_idx, io_uring_get_opcode(opcode), sqe->fd,
 			   sqe->flags, (unsigned long long) sqe->off,
 			   (unsigned long long) sqe->addr, sqe->rw_flags,
 			   sqe->buf_index, sqe->user_data);
-		if (sq_shift) {
+		if (sqe128) {
 			u64 *sqeb = (void *) (sqe + 1);
 			int size = sizeof(struct io_uring_sqe) / sizeof(u64);
 			int j;
@@ -120,6 +139,7 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
 			}
 		}
 		seq_printf(m, "\n");
+		sq_head++;
 	}
 	seq_printf(m, "CQEs:\t%u\n", cq_tail - cq_head);
 	while (cq_head < cq_tail) {
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index c397118da85e2..1e9748f25fbce 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2164,7 +2164,7 @@ static __cold int io_init_fail_req(struct io_kiocb *req, int err)
 }
 
 static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
-		       const struct io_uring_sqe *sqe)
+		       const struct io_uring_sqe *sqe, unsigned int *left)
 	__must_hold(&ctx->uring_lock)
 {
 	const struct io_issue_def *def;
@@ -2190,6 +2190,24 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
 	opcode = array_index_nospec(opcode, IORING_OP_LAST);
 
 	def = &io_issue_defs[opcode];
+	if (def->is_128 && !(ctx->flags & IORING_SETUP_SQE128)) {
+		/*
+		 * A 128b op on a non-128b SQ requires mixed SQE support as
+		 * well as 2 contiguous entries.
+		 */
+		if (!(ctx->flags & IORING_SETUP_SQE_MIXED) || *left < 2 ||
+		    !(ctx->cached_sq_head & (ctx->sq_entries - 1)))
+			return io_init_fail_req(req, -EINVAL);
+		/*
+		 * A 128b operation on a mixed SQ uses two entries, so we have
+		 * to increment the head and cached refs, and decrement what's
+		 * left.
+		 */
+		current->io_uring->cached_refs++;
+		ctx->cached_sq_head++;
+		(*left)--;
+	}
+
 	if (unlikely(sqe_flags & ~SQE_COMMON_FLAGS)) {
 		/* enforce forwards compatibility on users */
 		if (sqe_flags & ~SQE_VALID_FLAGS)
@@ -2299,13 +2317,13 @@ static __cold int io_submit_fail_init(const struct io_uring_sqe *sqe,
 }
 
 static inline int io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
-			 const struct io_uring_sqe *sqe)
+			 const struct io_uring_sqe *sqe, unsigned int *left)
 	__must_hold(&ctx->uring_lock)
 {
 	struct io_submit_link *link = &ctx->submit_state.link;
 	int ret;
 
-	ret = io_init_req(ctx, req, sqe);
+	ret = io_init_req(ctx, req, sqe, left);
 	if (unlikely(ret))
 		return io_submit_fail_init(sqe, req, ret);
 
@@ -2457,7 +2475,7 @@ int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
 		 * Continue submitting even for sqe failure if the
 		 * ring was setup with IORING_SETUP_SUBMIT_ALL
 		 */
-		if (unlikely(io_submit_sqe(ctx, req, sqe)) &&
+		if (unlikely(io_submit_sqe(ctx, req, sqe, &left)) &&
 		    !(ctx->flags & IORING_SETUP_SUBMIT_ALL)) {
 			left--;
 			break;
@@ -2802,6 +2820,10 @@ unsigned long rings_size(unsigned int flags, unsigned int sq_entries,
 		if (cq_entries < 2)
 			return SIZE_MAX;
 	}
+	if (flags & IORING_SETUP_SQE_MIXED) {
+		if (sq_entries < 2)
+			return SIZE_MAX;
+	}
 
 #ifdef CONFIG_SMP
 	off = ALIGN(off, SMP_CACHE_BYTES);
@@ -3728,6 +3750,13 @@ static int io_uring_sanitise_params(struct io_uring_params *p)
 	if ((flags & (IORING_SETUP_CQE32|IORING_SETUP_CQE_MIXED)) ==
 	    (IORING_SETUP_CQE32|IORING_SETUP_CQE_MIXED))
 		return -EINVAL;
+	/*
+	 * Nonsensical to ask for SQE128 and mixed SQE support, it's not
+	 * supported to post 64b SQEs on a ring setup with SQE128.
+	 */
+	if ((flags & (IORING_SETUP_SQE128|IORING_SETUP_SQE_MIXED)) ==
+	    (IORING_SETUP_SQE128|IORING_SETUP_SQE_MIXED))
+		return -EINVAL;
 
 	return 0;
 }
diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index 78777bf1ea4b9..44b8091c7fcdb 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -54,7 +54,8 @@
 			IORING_SETUP_REGISTERED_FD_ONLY |\
 			IORING_SETUP_NO_SQARRAY |\
 			IORING_SETUP_HYBRID_IOPOLL |\
-			IORING_SETUP_CQE_MIXED)
+			IORING_SETUP_CQE_MIXED |\
+			IORING_SETUP_SQE_MIXED)
 
 #define IORING_ENTER_FLAGS (IORING_ENTER_GETEVENTS |\
 			IORING_ENTER_SQ_WAKEUP |\
@@ -565,17 +566,6 @@ static inline void io_req_queue_tw_complete(struct io_kiocb *req, s32 res)
 	io_req_task_work_add(req);
 }
 
-/*
- * IORING_SETUP_SQE128 contexts allocate twice the normal SQE size for each
- * slot.
- */
-static inline size_t uring_sqe_size(struct io_ring_ctx *ctx)
-{
-	if (ctx->flags & IORING_SETUP_SQE128)
-		return 2 * sizeof(struct io_uring_sqe);
-	return sizeof(struct io_uring_sqe);
-}
-
 static inline bool io_file_can_poll(struct io_kiocb *req)
 {
 	if (req->flags & REQ_F_CAN_POLL)
diff --git a/io_uring/opdef.c b/io_uring/opdef.c
index 932319633eac2..df52d760240e4 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -575,6 +575,24 @@ const struct io_issue_def io_issue_defs[] = {
 		.prep			= io_pipe_prep,
 		.issue			= io_pipe,
 	},
+	[IORING_OP_NOP128] = {
+		.audit_skip		= 1,
+		.iopoll			= 1,
+		.is_128			= 1,
+		.prep			= io_nop_prep,
+		.issue			= io_nop,
+	},
+	[IORING_OP_URING_CMD128] = {
+		.buffer_select		= 1,
+		.needs_file		= 1,
+		.plug			= 1,
+		.iopoll			= 1,
+		.iopoll_queue		= 1,
+		.is_128			= 1,
+		.async_size		= sizeof(struct io_async_cmd),
+		.prep			= io_uring_cmd_prep,
+		.issue			= io_uring_cmd,
+	},
 };
 
 const struct io_cold_def io_cold_defs[] = {
@@ -825,6 +843,14 @@ const struct io_cold_def io_cold_defs[] = {
 	[IORING_OP_PIPE] = {
 		.name			= "PIPE",
 	},
+	[IORING_OP_NOP128] = {
+		.name			= "NOP128",
+	},
+	[IORING_OP_URING_CMD128] = {
+		.name			= "URING_CMD128",
+		.sqe_copy		= io_uring_cmd_sqe_copy,
+		.cleanup		= io_uring_cmd_cleanup,
+	},
 };
 
 const char *io_uring_get_opcode(u8 opcode)
diff --git a/io_uring/opdef.h b/io_uring/opdef.h
index c2f0907ed78cc..aa37846880ffd 100644
--- a/io_uring/opdef.h
+++ b/io_uring/opdef.h
@@ -27,6 +27,8 @@ struct io_issue_def {
 	unsigned		iopoll_queue : 1;
 	/* vectored opcode, set if 1) vectored, and 2) handler needs to know */
 	unsigned		vectored : 1;
+	/* set to 1 if this opcode uses 128b sqes in a mixed sq */
+	unsigned		is_128 : 1;
 
 	/* size of async data needed, if any */
 	unsigned short		async_size;
diff --git a/io_uring/register.c b/io_uring/register.c
index 2e4717f1357c7..df6c420ae01bb 100644
--- a/io_uring/register.c
+++ b/io_uring/register.c
@@ -395,7 +395,7 @@ static void io_register_free_rings(struct io_ring_ctx *ctx,
 #define RESIZE_FLAGS	(IORING_SETUP_CQSIZE | IORING_SETUP_CLAMP)
 #define COPY_FLAGS	(IORING_SETUP_NO_SQARRAY | IORING_SETUP_SQE128 | \
 			 IORING_SETUP_CQE32 | IORING_SETUP_NO_MMAP | \
-			 IORING_SETUP_CQE_MIXED)
+			 IORING_SETUP_CQE_MIXED | IORING_SETUP_SQE_MIXED)
 
 static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 {
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 1225f8124e4bb..9d67a2a721aa3 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -216,6 +216,18 @@ int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	return 0;
 }
 
+/*
+ * IORING_SETUP_SQE128 contexts allocate twice the normal SQE size for each
+ * slot.
+ */
+static inline size_t uring_sqe_size(struct io_kiocb *req)
+{
+	if (req->ctx->flags & IORING_SETUP_SQE128 ||
+	    req->opcode == IORING_OP_URING_CMD128)
+		return 2 * sizeof(struct io_uring_sqe);
+	return sizeof(struct io_uring_sqe);
+}
+
 void io_uring_cmd_sqe_copy(struct io_kiocb *req)
 {
 	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
@@ -224,7 +236,7 @@ void io_uring_cmd_sqe_copy(struct io_kiocb *req)
 	/* Should not happen, as REQ_F_SQE_COPIED covers this */
 	if (WARN_ON_ONCE(ioucmd->sqe == ac->sqes))
 		return;
-	memcpy(ac->sqes, ioucmd->sqe, uring_sqe_size(req->ctx));
+	memcpy(ac->sqes, ioucmd->sqe, uring_sqe_size(req));
 	ioucmd->sqe = ac->sqes;
 }
 
@@ -242,7 +254,8 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
 	if (ret)
 		return ret;
 
-	if (ctx->flags & IORING_SETUP_SQE128)
+	if (ctx->flags & IORING_SETUP_SQE128 ||
+	    req->opcode == IORING_OP_URING_CMD128)
 		issue_flags |= IO_URING_F_SQE128;
 	if (ctx->flags & (IORING_SETUP_CQE32 | IORING_SETUP_CQE_MIXED))
 		issue_flags |= IO_URING_F_CQE32;
-- 
2.47.3

Re: [PATCHv6] io_uring: add support for IORING_SETUP_SQE_MIXED

[Jens Axboe]

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

Best regards,
-- 
Jens Axboe

Re: [PATCHv6] io_uring: add support for IORING_SETUP_SQE_MIXED

[Nathan Chancellor]

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) {

Re: [PATCHv6] io_uring: add support for IORING_SETUP_SQE_MIXED

[Jens Axboe]

On 10/22/25 6:00 AM, Nathan Chancellor wrote:
> 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.

Indeed - I'll fold this in. Keith, can you add an fdinfo test case for
mixed as well?

-- 
Jens Axboe

Re: [PATCHv6] io_uring: add support for IORING_SETUP_SQE_MIXED

[Keith Busch]

On Wed, Oct 22, 2025 at 07:34:22AM -0600, Jens Axboe wrote:
> On 10/22/25 6:00 AM, Nathan Chancellor wrote:
> > 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.
> 
> Indeed - I'll fold this in. Keith, can you add an fdinfo test case for
> mixed as well?

Thanks, and will do. Any quick hints on how to ensure fdinfo finds some
entries to report? I assume I can just put some entries on the queue,
but don't call io_uring_enter.

Re: [PATCHv6] io_uring: add support for IORING_SETUP_SQE_MIXED

[Jens Axboe]

On 10/22/25 7:53 AM, Keith Busch wrote:
> On Wed, Oct 22, 2025 at 07:34:22AM -0600, Jens Axboe wrote:
>> On 10/22/25 6:00 AM, Nathan Chancellor wrote:
>>> 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.
>>
>> Indeed - I'll fold this in. Keith, can you add an fdinfo test case for
>> mixed as well?
> 
> Thanks, and will do. Any quick hints on how to ensure fdinfo finds some
> entries to report? I assume I can just put some entries on the queue,
> but don't call io_uring_enter.

Yep that should do it. You probably want to do something similar to
__io_uring_flush_sq() since it needs to be visible on the kernel side,
by having the SQ tail written too. io_uring_submit() does this, but
you'd want to do it without calling io_uring_enter() to submit the
entries.

And then probably do that with various states of mixed sized SQEs in the
SQ ring and verify it looks correct, too.

-- 
Jens Axboe