[PATCH V5 02/16] io_uring: add IORING_OP_FUSED_CMD

Ming Lei
2023-03-28T15:20:08Z

Add IORING_OP_FUSED_CMD, it is one special URING_CMD, which has to
be SQE128. The 1st SQE(primary) is one 64byte URING_CMD, and the 2nd
64byte SQE(secondary) is another normal 64byte OP. For any OP which needs
to support secondary OP, io_issue_defs[op].fused_secondary has to be set as 1,
and its ->issue() needs to retrieve buffer from primary request's
fused_cmd_kbuf.

Follows the key points of the design/implementation:

1) The primary uring command produces and provides immutable command
buffer(struct io_uring_bvec_buf) to the secondary request, and the secondary
OP can retrieve any part of this buffer by sqe->addr and sqe->len.

2) Master command is always completed after the secondary request is
completed, so secondary request can be thought as serving for primary
command.

- secondary request borrows primary command's buffer(io_uring_bvec_buf), after
secondary request is completed, the buffer is returned back to primary request.

- This way also guarantees correct SQE order since the primary
request uses secondary request's LINK flag.

3) Master request completion is always notified to driver, so that driver
can know when the buffer is done with secondary quest. This way is important
since io_uring_bvec_buf represents reference of device io command buffer,
and we have to gurantee that reference can not outlive the referent buffer,
so far which is represented by bvec.

4) kernel API of io_fused_cmd_start_secondary_req is called by driver for
making the buffer of io_uring_bvec_buf and starting to submit secondary
request with the provided buffer.

The motivation is for supporting zero copy for fuse/ublk, in which
the device holds IO request buffer, and IO handling is often normal
IO OP(fs, net, ..). With IORING_OP_FUSED_CMD, we can implement this kind
of zero copy easily & reliably.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
include/linux/io_uring.h | 50 ++++++-
include/linux/io_uring_types.h | 12 ++
include/uapi/linux/io_uring.h | 3 +
io_uring/Makefile | 2 +-
io_uring/fused_cmd.c | 241 +++++++++++++++++++++++++++++++++
io_uring/fused_cmd.h | 11 ++
io_uring/io_uring.c | 26 +++-
io_uring/io_uring.h | 3 +
io_uring/opdef.c | 12 ++
io_uring/opdef.h | 7 +
10 files changed, 361 insertions(+), 6 deletions(-)
create mode 100644 io_uring/fused_cmd.c
create mode 100644 io_uring/fused_cmd.h

diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index 35b9328ca335..fdb48fff8313 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -4,6 +4,7 @@

#include <linux/sched.h>
#include <linux/xarray.h>
+#include <linux/bvec.h>
#include <uapi/linux/io_uring.h>

enum io_uring_cmd_flags {
@@ -20,6 +21,26 @@ enum io_uring_cmd_flags {
IO_URING_F_SQE128 = (1 << 8),
IO_URING_F_CQE32 = (1 << 9),
IO_URING_F_IOPOLL = (1 << 10),
+
+ /* for FUSED_CMD only */
+ IO_URING_F_FUSED_BUF_DEST = (1 << 11), /* secondary write to buffer */
+ IO_URING_F_FUSED_BUF_SRC = (1 << 12), /* secondary read from buffer */
+ /* driver incapable of FUSED_CMD should fail cmd when seeing F_FUSED */
+ IO_URING_F_FUSED = IO_URING_F_FUSED_BUF_DEST |
+ IO_URING_F_FUSED_BUF_SRC,
+};
+
+union io_uring_fused_cmd_data {
+ /*
+ * In case of secondary request IOSQE_CQE_SKIP_SUCCESS, return the
+ * result via primary command; otherwise we simply return success
+ * if buffer is provided, and secondary request will return its result
+ * via its CQE
+ */
+ s32 secondary_res;
+
+ /* fused cmd private, driver do not touch it */
+ struct io_kiocb *__secondary;
};

struct io_uring_cmd {
@@ -33,10 +54,31 @@ struct io_uring_cmd {
};
u32 cmd_op;
u32 flags;
- u8 pdu[32]; /* available inline for free use */
+
+ /* for fused command, the available pdu is a bit less */
+ union {
+ struct {
+ union io_uring_fused_cmd_data data;
+ u8 pdu[24]; /* available inline for free use */
+ } fused;
+ u8 pdu[32]; /* available inline for free use */
+ };
+};
+
+struct io_uring_bvec_buf {
+ unsigned long len;
+ unsigned int nr_bvecs;
+
+ /* offset in the 1st bvec */
+ unsigned int offset;
+ const struct bio_vec *bvec;
+ struct bio_vec __bvec[];
};

#if defined(CONFIG_IO_URING)
+void io_fused_cmd_start_secondary_req(struct io_uring_cmd *, unsigned,
+ const struct io_uring_bvec_buf *,
+ void (*complete_tw_cb)(struct io_uring_cmd *, unsigned));
int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
struct iov_iter *iter, void *ioucmd);
void io_uring_cmd_done(struct io_uring_cmd *cmd, ssize_t ret, ssize_t res2,
@@ -67,6 +109,12 @@ static inline void io_uring_free(struct task_struct *tsk)
__io_uring_free(tsk);
}
#else
+static inline void io_fused_cmd_start_secondary_req(struct io_uring_cmd *,
+ unsigned issue_flags, const struct io_uring_bvec_buf *,
+ unsigned int,
+ void (*complete_tw_cb)(struct io_uring_cmd *, unsigned))
+{
+}
static inline int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
struct iov_iter *iter, void *ioucmd)
{
diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index dd8ef886730b..9c427f1e00e6 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -407,6 +407,7 @@ enum {
/* keep async read/write and isreg together and in order */
REQ_F_SUPPORT_NOWAIT_BIT,
REQ_F_ISREG_BIT,
+ REQ_F_FUSED_SECONDARY_BIT,

/* not a real bit, just to check we're not overflowing the space */
__REQ_F_LAST_BIT,
@@ -476,6 +477,8 @@ enum {
REQ_F_CLEAR_POLLIN = BIT_ULL(REQ_F_CLEAR_POLLIN_BIT),
/* hashed into ->cancel_hash_locked, protected by ->uring_lock */
REQ_F_HASH_LOCKED = BIT_ULL(REQ_F_HASH_LOCKED_BIT),
+ /* secondary request in fused cmd, won't be one uring cmd */
+ REQ_F_FUSED_SECONDARY = BIT_ULL(REQ_F_FUSED_SECONDARY_BIT),
};

typedef void (*io_req_tw_func_t)(struct io_kiocb *req, struct io_tw_state *ts);
@@ -558,6 +561,15 @@ struct io_kiocb {
* REQ_F_BUFFER_RING is set.
*/
struct io_buffer_list *buf_list;
+
+ /*
+ * store kernel (sub)buffer of fused primary request which OP
+ * is IORING_OP_FUSED_CMD
+ */
+ const struct io_uring_bvec_buf *fused_cmd_kbuf;
+
+ /* store fused command's primary request for the secondary */
+ struct io_kiocb *fused_primary_req;
};

union {
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index f8d14d1c58d3..98b7f21623f9 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -73,6 +73,8 @@ struct io_uring_sqe {
__u16 buf_index;
/* for grouped buffer selection */
__u16 buf_group;
+ /* how many secondary normal SQEs following this fused SQE */
+ __u16 nr_secondary;
} __attribute__((packed));
/* personality to use, if used */
__u16 personality;
@@ -223,6 +225,7 @@ enum io_uring_op {
IORING_OP_URING_CMD,
IORING_OP_SEND_ZC,
IORING_OP_SENDMSG_ZC,
+ IORING_OP_FUSED_CMD,

/* this goes last, obviously */
IORING_OP_LAST,
diff --git a/io_uring/Makefile b/io_uring/Makefile
index 8cc8e5387a75..5301077e61c5 100644
--- a/io_uring/Makefile
+++ b/io_uring/Makefile
@@ -7,5 +7,5 @@ obj-$(CONFIG_IO_URING) += io_uring.o xattr.o nop.o fs.o splice.o \
openclose.o uring_cmd.o epoll.o \
statx.o net.o msg_ring.o timeout.o \
sqpoll.o fdinfo.o tctx.o poll.o \
- cancel.o kbuf.o rsrc.o rw.o opdef.o notif.o
+ cancel.o kbuf.o rsrc.o rw.o opdef.o notif.o fused_cmd.o
obj-$(CONFIG_IO_WQ) += io-wq.o
diff --git a/io_uring/fused_cmd.c b/io_uring/fused_cmd.c
new file mode 100644
index 000000000000..7af3ddb182c1
--- /dev/null
+++ b/io_uring/fused_cmd.c
@@ -0,0 +1,241 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/io_uring.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "io_uring.h"
+#include "opdef.h"
+#include "rsrc.h"
+#include "uring_cmd.h"
+#include "fused_cmd.h"
+
+static bool io_fused_secondary_valid(const struct io_uring_sqe *sqe, u8 op)
+{
+ unsigned int sqe_flags = READ_ONCE(sqe->flags);
+
+ if (op == IORING_OP_FUSED_CMD || op == IORING_OP_URING_CMD)
+ return false;
+
+ if (sqe_flags & REQ_F_BUFFER_SELECT)
+ return false;
+
+ if (!io_issue_defs[op].fused_secondary)
+ return false;
+
+ return true;
+}
+
+static inline void io_fused_cmd_update_link_flags(struct io_kiocb *req,
+ const struct io_kiocb *secondary)
+{
+ /*
+ * We have to keep secondary SQE in order, so update primary link flags
+ * with secondary request's given primary command isn't completed until
+ * the secondary request is done
+ */
+ if (secondary->flags & (REQ_F_LINK | REQ_F_HARDLINK))
+ req->flags |= REQ_F_LINK;
+}
+
+int io_fused_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+ __must_hold(&req->ctx->uring_lock)
+{
+ struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
+ const struct io_uring_sqe *secondary_sqe = sqe + 1;
+ struct io_ring_ctx *ctx = req->ctx;
+ struct io_kiocb *secondary;
+ u8 secondary_op;
+ int ret;
+
+ if (unlikely(!(ctx->flags & IORING_SETUP_SQE128)))
+ return -EINVAL;
+
+ if (unlikely(sqe->__pad1))
+ return -EINVAL;
+
+ /*
+ * So far, only support single secondary request, in future we may
+ * extend to support multiple secondary requests
+ */
+ if (unlikely(sqe->nr_secondary != 1))
+ return -EINVAL;
+
+ ioucmd->flags = READ_ONCE(sqe->uring_cmd_flags);
+ if (unlikely(ioucmd->flags))
+ return -EINVAL;
+
+ secondary_op = READ_ONCE(secondary_sqe->opcode);
+ if (unlikely(!io_fused_secondary_valid(secondary_sqe, secondary_op)))
+ return -EINVAL;
+
+ ioucmd->cmd = sqe->cmd;
+ ioucmd->cmd_op = READ_ONCE(sqe->cmd_op);
+ req->fused_cmd_kbuf = NULL;
+
+ /* take one extra reference for the secondary request */
+ io_get_task_refs(1);
+
+ ret = -ENOMEM;
+ if (unlikely(!io_alloc_req(ctx, &secondary)))
+ goto fail;
+
+ ret = io_init_secondary_req(ctx, secondary, secondary_sqe);
+ if (unlikely(ret))
+ goto fail_free_req;
+
+ /*
+ * The secondary request won't be linked to io_uring submission link list,
+ * so it can't be handled by IORING_OP_LINK_TIMEOUT, however, we can do
+ * that on primary command directly
+ */
+ io_fused_cmd_update_link_flags(req, secondary);
+
+ ioucmd->fused.data.__secondary = secondary;
+
+ return 0;
+
+fail_free_req:
+ io_free_req(secondary);
+fail:
+ current->io_uring->cached_refs += 1;
+ return ret;
+}
+
+int io_fused_cmd(struct io_kiocb *req, unsigned int issue_flags)
+{
+ struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
+ const struct io_kiocb *secondary = ioucmd->fused.data.__secondary;
+ int ret = -EINVAL;
+
+ /*
+ * Pass buffer direction for driver to validate if the requested buffer
+ * direction is legal
+ */
+ if (io_issue_defs[secondary->opcode].buf_dir)
+ issue_flags |= IO_URING_F_FUSED_BUF_DEST;
+ else
+ issue_flags |= IO_URING_F_FUSED_BUF_SRC;
+
+ ret = io_uring_cmd(req, issue_flags);
+ if (ret != IOU_ISSUE_SKIP_COMPLETE)
+ io_free_req(ioucmd->fused.data.__secondary);
+
+ return ret;
+}
+
+int io_import_buf_for_secondary(unsigned long buf_off, unsigned int len,
+ int dir, struct iov_iter *iter, struct io_kiocb *secondary)
+{
+ struct io_kiocb *req = secondary->fused_primary_req;
+ const struct io_uring_bvec_buf *kbuf;
+ unsigned long offset;
+
+ if (unlikely(!(secondary->flags & REQ_F_FUSED_SECONDARY) || !req))
+ return -EINVAL;
+
+ if (unlikely(!req->fused_cmd_kbuf))
+ return -EINVAL;
+
+ /* req->fused_cmd_kbuf is immutable */
+ kbuf = req->fused_cmd_kbuf;
+ offset = kbuf->offset;
+
+ if (!kbuf->bvec)
+ return -EINVAL;
+
+ if (unlikely(buf_off > kbuf->len))
+ return -EFAULT;
+
+ if (unlikely(len > kbuf->len - buf_off))
+ return -EFAULT;
+
+ /* don't use io_import_fixed which doesn't support multipage bvec */
+ offset += buf_off;
+ iov_iter_bvec(iter, dir, kbuf->bvec, kbuf->nr_bvecs, offset + len);
+
+ if (offset)
+ iov_iter_advance(iter, offset);
+
+ return 0;
+}
+
+/*
+ * Called after secondary request is completed,
+ *
+ * Return back primary's fused_cmd kbuf, and notify primary request by
+ * the saved callback.
+ */
+void io_fused_cmd_return_buf(struct io_kiocb *secondary)
+{
+ struct io_kiocb *req = secondary->fused_primary_req;
+ struct io_uring_cmd *ioucmd;
+
+ if (unlikely(!req || !(secondary->flags & REQ_F_FUSED_SECONDARY)))
+ return;
+
+ /* return back the buffer */
+ secondary->fused_primary_req = NULL;
+ ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
+ ioucmd->fused.data.__secondary = NULL;
+
+ /*
+ * If secondary OP skips CQE, return the result via primary command; or
+ * if secondary request is failed, REQ_F_CQE_SKIP will be cleared, return
+ * result too
+ */
+ if ((secondary->flags & REQ_F_CQE_SKIP) || secondary->cqe.res < 0)
+ ioucmd->fused.data.secondary_res = secondary->cqe.res;
+ else
+ ioucmd->fused.data.secondary_res = 0;
+ io_uring_cmd_complete_in_task(ioucmd, ioucmd->task_work_cb);
+}
+
+/*
+ * Called for starting secondary request after primary command prepared io buffer.
+ *
+ * The io buffer is represented by @fused_cmd_kbuf, which is read only for
+ * secondary request, however secondary request can retrieve any sub-buffer by its
+ * sqe->addr(offset) & sqe->len. For secondary request, io buffer is imported
+ * by io_import_buf_for_secondary().
+ *
+ * Slave request borrows primary's io buffer for handling the secondary operation,
+ * and the buffer is returned back via io_fused_cmd_return_buf after the secondary
+ * request is completed. Meantime the primary command is completed from
+ * io_fused_cmd_return_buf(). And driver gets completion notification by
+ * the passed callback of @complete_tw_cb.
+ */
+void io_fused_cmd_start_secondary_req(struct io_uring_cmd *ioucmd,
+ unsigned issue_flags,
+ const struct io_uring_bvec_buf *fused_cmd_kbuf,
+ void (*complete_tw_cb)(struct io_uring_cmd *, unsigned))
+{
+ struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
+ struct io_kiocb *secondary = ioucmd->fused.data.__secondary;
+ struct io_tw_state ts = {
+ .locked = !(issue_flags & IO_URING_F_UNLOCKED),
+ };
+
+ if (WARN_ON_ONCE(unlikely(!secondary || !(secondary->flags &
+ REQ_F_FUSED_SECONDARY))))
+ return;
+
+ /*
+ * Once the fused secondary request is completed and the buffer isn't be
+ * used, the driver will be notified by callback of complete_tw_cb
+ */
+ ioucmd->task_work_cb = complete_tw_cb;
+
+ /* now we get the buffer */
+ req->fused_cmd_kbuf = fused_cmd_kbuf;
+ secondary->fused_primary_req = req;
+
+ trace_io_uring_submit_sqe(secondary, true);
+ io_req_task_submit(secondary, &ts);
+}
+EXPORT_SYMBOL_GPL(io_fused_cmd_start_secondary_req);
diff --git a/io_uring/fused_cmd.h b/io_uring/fused_cmd.h
new file mode 100644
index 000000000000..c75e5d8c5763
--- /dev/null
+++ b/io_uring/fused_cmd.h
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef IOU_FUSED_CMD_H
+#define IOU_FUSED_CMD_H
+
+int io_fused_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_fused_cmd(struct io_kiocb *req, unsigned int issue_flags);
+void io_fused_cmd_return_buf(struct io_kiocb *secondary);
+int io_import_buf_for_secondary(unsigned long buf, unsigned int len, int dir,
+ struct iov_iter *iter, struct io_kiocb *secondary);
+
+#endif
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 693558c4b10b..ddbc9b9e51d3 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -92,6 +92,7 @@
#include "cancel.h"
#include "net.h"
#include "notif.h"
+#include "fused_cmd.h"

#include "timeout.h"
#include "poll.h"
@@ -111,7 +112,7 @@

#define IO_REQ_CLEAN_FLAGS (REQ_F_BUFFER_SELECTED | REQ_F_NEED_CLEANUP | \
REQ_F_POLLED | REQ_F_INFLIGHT | REQ_F_CREDS | \
- REQ_F_ASYNC_DATA)
+ REQ_F_ASYNC_DATA | REQ_F_FUSED_SECONDARY)

#define IO_REQ_CLEAN_SLOW_FLAGS (REQ_F_REFCOUNT | REQ_F_LINK | REQ_F_HARDLINK |\
IO_REQ_CLEAN_FLAGS)
@@ -971,6 +972,9 @@ static void __io_req_complete_post(struct io_kiocb *req)
{
struct io_ring_ctx *ctx = req->ctx;

+ if (req->flags & REQ_F_FUSED_SECONDARY)
+ io_fused_cmd_return_buf(req);
+
io_cq_lock(ctx);
if (!(req->flags & REQ_F_CQE_SKIP))
io_fill_cqe_req(ctx, req);
@@ -1855,6 +1859,8 @@ static void io_clean_op(struct io_kiocb *req)
spin_lock(&req->ctx->completion_lock);
io_put_kbuf_comp(req);
spin_unlock(&req->ctx->completion_lock);
+ } else if (req->flags & REQ_F_FUSED_SECONDARY) {
+ io_fused_cmd_return_buf(req);
}

if (req->flags & REQ_F_NEED_CLEANUP) {
@@ -2163,8 +2169,8 @@ static void io_init_req_drain(struct io_kiocb *req)
}
}

-static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
- const struct io_uring_sqe *sqe)
+static inline int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
+ const struct io_uring_sqe *sqe, bool secondary)
__must_hold(&ctx->uring_lock)
{
const struct io_issue_def *def;
@@ -2217,6 +2223,12 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
}
}

+ if (secondary) {
+ if (!def->fused_secondary)
+ return -EINVAL;
+ req->flags |= REQ_F_FUSED_SECONDARY;
+ }
+
if (!def->ioprio && sqe->ioprio)
return -EINVAL;
if (!def->iopoll && (ctx->flags & IORING_SETUP_IOPOLL))
@@ -2257,6 +2269,12 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
return def->prep(req, sqe);
}

+int io_init_secondary_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
+ const struct io_uring_sqe *sqe)
+{
+ return io_init_req(ctx, req, sqe, true);
+}
+
static __cold int io_submit_fail_init(const struct io_uring_sqe *sqe,
struct io_kiocb *req, int ret)
{
@@ -2301,7 +2319,7 @@ static inline int io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
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, false);
if (unlikely(ret))
return io_submit_fail_init(sqe, req, ret);

diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index c33f719731ac..dd193c612348 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -78,6 +78,9 @@ bool __io_alloc_req_refill(struct io_ring_ctx *ctx);
bool io_match_task_safe(struct io_kiocb *head, struct task_struct *task,
bool cancel_all);

+int io_init_secondary_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
+ const struct io_uring_sqe *sqe);
+
#define io_lockdep_assert_cq_locked(ctx) \
do { \
if (ctx->flags & IORING_SETUP_IOPOLL) { \
diff --git a/io_uring/opdef.c b/io_uring/opdef.c
index cca7c5b55208..63b90e8e65f8 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -33,6 +33,7 @@
#include "poll.h"
#include "cancel.h"
#include "rw.h"
+#include "fused_cmd.h"

static int io_no_issue(struct io_kiocb *req, unsigned int issue_flags)
{
@@ -428,6 +429,12 @@ const struct io_issue_def io_issue_defs[] = {
.prep = io_eopnotsupp_prep,
#endif
},
+ [IORING_OP_FUSED_CMD] = {
+ .needs_file = 1,
+ .plug = 1,
+ .prep = io_fused_cmd_prep,
+ .issue = io_fused_cmd,
+ },
};

@@ -648,6 +655,11 @@ const struct io_cold_def io_cold_defs[] = {
.fail = io_sendrecv_fail,
#endif
},
+ [IORING_OP_FUSED_CMD] = {
+ .name = "FUSED_CMD",
+ .async_size = uring_cmd_pdu_size(1),
+ .prep_async = io_uring_cmd_prep_async,
+ },
};

const char *io_uring_get_opcode(u8 opcode)
diff --git a/io_uring/opdef.h b/io_uring/opdef.h
index c22c8696e749..bded61ebcbfc 100644
--- a/io_uring/opdef.h
+++ b/io_uring/opdef.h
@@ -29,6 +29,13 @@ struct io_issue_def {
unsigned iopoll_queue : 1;
/* opcode specific path will handle ->async_data allocation if needed */
unsigned manual_alloc : 1;
+ /* can be secondary op of fused command */
+ unsigned fused_secondary : 1;
+ /*
+ * buffer direction, 0 : read from buffer, 1: write to buffer, used
+ * for fused_secondary only
+ */
+ unsigned buf_dir : 1;

int (*issue)(struct io_kiocb *, unsigned int);
int (*prep)(struct io_kiocb *, const struct io_uring_sqe *);
--
2.39.2