[PATCH 2/4] io_uring: add flags2 variable

[Jens Axboe <axboe@kernel.dk>]

Most opcodes don't support using the ioprio field, it's really only
something that read/write to storage media supports. Overlay a flags2
variable with ioprio, so we can grow our flags space.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io_uring.c                 | 40 ++++++++++++++++++++++++-----------
 include/uapi/linux/io_uring.h |  8 ++++++-
 2 files changed, 35 insertions(+), 13 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 29153958ea78..06afe4db5a9a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -108,7 +108,10 @@
 			  IOSQE_IO_HARDLINK | IOSQE_ASYNC)
 
 #define SQE_VALID_FLAGS	(SQE_COMMON_FLAGS | IOSQE_BUFFER_SELECT | \
-			IOSQE_IO_DRAIN | IOSQE_CQE_SKIP_SUCCESS)
+			IOSQE_IO_DRAIN | IOSQE_CQE_SKIP_SUCCESS | \
+			IOSQE_FLAGS2)
+
+#define SQE_VALID_FLAGS2	0
 
 #define IO_REQ_CLEAN_FLAGS (REQ_F_BUFFER_SELECTED | REQ_F_NEED_CLEANUP | \
 				REQ_F_POLLED | REQ_F_CREDS | REQ_F_ASYNC_DATA)
@@ -788,9 +791,10 @@ enum {
 	REQ_F_FORCE_ASYNC_BIT	= IOSQE_ASYNC_BIT,
 	REQ_F_BUFFER_SELECT_BIT	= IOSQE_BUFFER_SELECT_BIT,
 	REQ_F_CQE_SKIP_BIT	= IOSQE_CQE_SKIP_SUCCESS_BIT,
+	REQ_F_FLAGS2_BIT	= IOSQE_FLAGS2_BIT,
 
-	/* first byte is taken by user flags, shift it to not overlap */
-	REQ_F_FAIL_BIT		= 8,
+	/* first bits are taken by user flags, shift it to not overlap */
+	REQ_F_FAIL_BIT		= 9,
 	REQ_F_INFLIGHT_BIT,
 	REQ_F_CUR_POS_BIT,
 	REQ_F_NOWAIT_BIT,
@@ -831,6 +835,8 @@ enum {
 	REQ_F_BUFFER_SELECT	= BIT(REQ_F_BUFFER_SELECT_BIT),
 	/* IOSQE_CQE_SKIP_SUCCESS */
 	REQ_F_CQE_SKIP		= BIT(REQ_F_CQE_SKIP_BIT),
+	/* IOSQE_FLAGS2 */
+	REQ_F_FLAGS2		= BIT(REQ_F_FLAGS2_BIT),
 
 	/* fail rest of links */
 	REQ_F_FAIL		= BIT(REQ_F_FAIL_BIT),
@@ -3280,15 +3286,16 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 
 	kiocb->ki_pos = READ_ONCE(sqe->off);
 
-	ioprio = READ_ONCE(sqe->ioprio);
-	if (ioprio) {
-		ret = ioprio_check_cap(ioprio);
-		if (ret)
-			return ret;
+	kiocb->ki_ioprio = get_current_ioprio();
+	if (!(req->flags & REQ_F_FLAGS2)) {
+		ioprio = READ_ONCE(sqe->ioprio);
+		if (ioprio) {
+			ret = ioprio_check_cap(ioprio);
+			if (ret)
+				return ret;
 
-		kiocb->ki_ioprio = ioprio;
-	} else {
-		kiocb->ki_ioprio = get_current_ioprio();
+			kiocb->ki_ioprio = ioprio;
+		}
 	}
 
 	req->imu = NULL;
@@ -7779,6 +7786,14 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
 				return -EOPNOTSUPP;
 			io_init_req_drain(req);
 		}
+		if (sqe_flags & IOSQE_FLAGS2) {
+			unsigned int sqe_flags2;
+
+			sqe_flags2 = READ_ONCE(sqe->flags2);
+			if (sqe_flags2 & ~SQE_VALID_FLAGS2)
+				return -EINVAL;
+			req->flags |= sqe_flags | (sqe_flags2 << 8U);
+		}
 	}
 	if (unlikely(ctx->restricted || ctx->drain_active || ctx->drain_next)) {
 		if (ctx->restricted && !io_check_restriction(ctx, req, sqe_flags))
@@ -7794,7 +7809,8 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
 		}
 	}
 
-	if (!io_op_defs[opcode].ioprio && sqe->ioprio)
+	if (!io_op_defs[opcode].ioprio && sqe->ioprio &&
+	    !(req->flags & REQ_F_FLAGS2))
 		return -EINVAL;
 	if (!io_op_defs[opcode].iopoll && (ctx->flags & IORING_SETUP_IOPOLL))
 		return -EINVAL;
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index fad63564678a..622f6e27a444 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -17,7 +17,10 @@
 struct io_uring_sqe {
 	__u8	opcode;		/* type of operation for this sqe */
 	__u8	flags;		/* IOSQE_ flags */
-	__u16	ioprio;		/* ioprio for the request */
+	union {
+		__u16	ioprio;	/* ioprio for the request */
+		__u16	flags2;	/* extra flags */
+	};
 	__s32	fd;		/* file descriptor to do IO on */
 	union {
 		__u64	off;	/* offset into file */
@@ -71,6 +74,7 @@ enum {
 	IOSQE_ASYNC_BIT,
 	IOSQE_BUFFER_SELECT_BIT,
 	IOSQE_CQE_SKIP_SUCCESS_BIT,
+	IOSQE_FLAGS2_BIT,
 };
 
 /*
@@ -90,6 +94,8 @@ enum {
 #define IOSQE_BUFFER_SELECT	(1U << IOSQE_BUFFER_SELECT_BIT)
 /* don't post CQE if request succeeded */
 #define IOSQE_CQE_SKIP_SUCCESS	(1U << IOSQE_CQE_SKIP_SUCCESS_BIT)
+/* flags2 is valid and set */
+#define IOSQE_FLAGS2		(1U << IOSQE_FLAGS2_BIT)
 
 /*
  * io_uring_setup() flags
-- 
2.35.1