[PATCH v2] io_uring: extend io_uring_sqe flags bits

[PATCH v2] io_uring: extend io_uring_sqe flags bits

[Jens Axboe]

In hindsight everything is clearer, but it probably should've been known
that 8 bits of ->flags would run out sooner than later. Rather than
gobble up the last bit for a random use case, add a bit that controls
whether or not ->personality is used as a flags2 argument. If that is
the case, then there's a new IOSQE2_PERSONALITY flag that tells io_uring
which personality field to read.

While this isn't the prettiest, it does allow extending with 15 extra
flags, and retains being able to use personality with any kind of
command. The exception is uring cmd, where personality2 will overlap
with the space set aside for SQE128. If they really need that, then that
would have to be done via a uring cmd flag.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

---

V2:
- Fix shift of fixed file flags
- Add a few comments
- Update trace event
- Nicer numbering
- Overlap flags2 with uring cmd, and leave addr3 free to be used with
  flags2

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index d52fec533c51..7b04d34aa8bb 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -438,6 +438,7 @@ struct io_tw_state {
 };
 
 enum {
+	/* 8 bits of sqe->flags */
 	REQ_F_FIXED_FILE_BIT	= IOSQE_FIXED_FILE_BIT,
 	REQ_F_IO_DRAIN_BIT	= IOSQE_IO_DRAIN_BIT,
 	REQ_F_LINK_BIT		= IOSQE_IO_LINK_BIT,
@@ -445,9 +446,16 @@ 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,
+	/* 16 bits of sqe->flags2 */
+	REQ_F_PERSONALITY_BIT	= IOSQE2_PERSONALITY_BIT,
+
+	/* first byte taken by sqe->flags, next 2 by sqe->flags2 */
+	REQ_F_FAIL_BIT		= 24,
+	/* keep async read/write and isreg together and in order */
+	REQ_F_SUPPORT_NOWAIT_BIT,
+	REQ_F_ISREG_BIT,
 	REQ_F_INFLIGHT_BIT,
 	REQ_F_CUR_POS_BIT,
 	REQ_F_NOWAIT_BIT,
@@ -467,9 +475,6 @@ enum {
 	REQ_F_DOUBLE_POLL_BIT,
 	REQ_F_APOLL_MULTISHOT_BIT,
 	REQ_F_CLEAR_POLLIN_BIT,
-	/* keep async read/write and isreg together and in order */
-	REQ_F_SUPPORT_NOWAIT_BIT,
-	REQ_F_ISREG_BIT,
 	REQ_F_POLL_NO_LAZY_BIT,
 	REQ_F_CAN_POLL_BIT,
 	REQ_F_BL_EMPTY_BIT,
@@ -498,6 +503,10 @@ enum {
 	REQ_F_BUFFER_SELECT	= IO_REQ_FLAG(REQ_F_BUFFER_SELECT_BIT),
 	/* IOSQE_CQE_SKIP_SUCCESS */
 	REQ_F_CQE_SKIP		= IO_REQ_FLAG(REQ_F_CQE_SKIP_BIT),
+	/* ->flags2 is valid */
+	REQ_F_FLAGS2		= IO_REQ_FLAG(REQ_F_FLAGS2_BIT),
+
+	REQ_F_PERSONALITY	= IO_REQ_FLAG(REQ_F_PERSONALITY_BIT),
 
 	/* fail rest of links */
 	REQ_F_FAIL		= IO_REQ_FLAG(REQ_F_FAIL_BIT),
diff --git a/include/trace/events/io_uring.h b/include/trace/events/io_uring.h
index fb81c533b310..07c3c0d80a7d 100644
--- a/include/trace/events/io_uring.h
+++ b/include/trace/events/io_uring.h
@@ -538,8 +538,8 @@ TRACE_EVENT(io_uring_req_failed,
 	TP_printk("ring %p, req %p, user_data 0x%llx, "
 		  "opcode %s, flags 0x%x, prio=%d, off=%llu, addr=%llu, "
 		  "len=%u, rw_flags=0x%x, buf_index=%d, "
-		  "personality=%d, file_index=%d, pad=0x%llx, addr3=%llx, "
-		  "error=%d",
+		  "personality/flags2=0x%x, file_index=%d, pad=0x%llx, "
+		  "addr3=%llx, error=%d",
 		  __entry->ctx, __entry->req, __entry->user_data,
 		  __get_str(op_str),
 		  __entry->flags, __entry->ioprio,
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 47977a5c65f5..d4cb2a90e94d 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -82,8 +82,12 @@ struct io_uring_sqe {
 		/* for grouped buffer selection */
 		__u16	buf_group;
 	} __attribute__((packed));
-	/* personality to use, if used */
-	__u16	personality;
+	union {
+		/* personality to use, if used */
+		__u16	personality;
+		/* 2nd set of flags, can't be used with personality */
+		__u16	flags2;
+	};
 	union {
 		__s32	splice_fd_in;
 		__u32	file_index;
@@ -96,7 +100,9 @@ struct io_uring_sqe {
 	union {
 		struct {
 			__u64	addr3;
-			__u64	__pad2[1];
+			/* personality to use, if IOSQE2_PERSONALITY set */
+			__u16	personality2;
+			__u16	__pad2[3];
 		};
 		__u64	optval;
 		/*
@@ -124,6 +130,11 @@ enum io_uring_sqe_flags_bit {
 	IOSQE_ASYNC_BIT,
 	IOSQE_BUFFER_SELECT_BIT,
 	IOSQE_CQE_SKIP_SUCCESS_BIT,
+	IOSQE_FLAGS2_BIT,
+};
+
+enum io_uring_sqe_flags2_bit {
+	IOSQE2_PERSONALITY_BIT	= IOSQE_FLAGS2_BIT + 1,
 };
 
 /*
@@ -143,6 +154,14 @@ enum io_uring_sqe_flags_bit {
 #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 */
+#define IOSQE_FLAGS2		(1U << IOSQE_FLAGS2_BIT)
+
+/*
+ * sqe->flags2
+ */
+ /* if set, sqe->personality2 contains personality */
+#define IOSQE2_PERSONALITY	(1U << IOSQE2_PERSONALITY_BIT)
 
 /*
  * io_uring_setup() flags
diff --git a/io_uring/filetable.h b/io_uring/filetable.h
index bfacadb8d089..2cf344c389c3 100644
--- a/io_uring/filetable.h
+++ b/io_uring/filetable.h
@@ -52,7 +52,7 @@ static inline struct file *io_slot_file(struct io_rsrc_node *node)
 static inline void io_fixed_file_set(struct io_rsrc_node *node,
 				     struct file *file)
 {
-	node->file_ptr = (unsigned long)file |
+	node->file_ptr = (__u64)file |
 		(io_file_get_flags(file) >> REQ_F_SUPPORT_NOWAIT_BIT);
 }
 
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 7a7a9b9718ec..729fe0a86c19 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -109,7 +109,8 @@
 			  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 | IOSQE2_PERSONALITY)
 
 #define IO_REQ_CLEAN_FLAGS (REQ_F_BUFFER_SELECTED | REQ_F_NEED_CLEANUP | \
 				REQ_F_POLLED | REQ_F_INFLIGHT | REQ_F_CREDS | \
@@ -2033,6 +2034,8 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
 	req->opcode = opcode = READ_ONCE(sqe->opcode);
 	/* same numerical values with corresponding REQ_F_*, safe to copy */
 	sqe_flags = READ_ONCE(sqe->flags);
+	if (sqe_flags & REQ_F_FLAGS2)
+		sqe_flags |= (__u32) READ_ONCE(sqe->flags2) << 8;
 	req->flags = (__force io_req_flags_t) sqe_flags;
 	req->cqe.user_data = READ_ONCE(sqe->user_data);
 	req->file = NULL;
@@ -2096,8 +2099,12 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
 		}
 	}
 
-	personality = READ_ONCE(sqe->personality);
-	if (personality) {
+	personality = 0;
+	if (req->flags & REQ_F_PERSONALITY)
+		personality = READ_ONCE(sqe->personality2);
+	else if (!(req->flags & REQ_F_FLAGS2))
+		personality = READ_ONCE(sqe->personality);
+	if (unlikely(personality)) {
 		int ret;
 
 		req->creds = xa_load(&ctx->personalities, personality);
@@ -3913,7 +3920,7 @@ static int __init io_uring_init(void)
 	BUILD_BUG_SQE_ELEM(46, __u16,  __pad3[0]);
 	BUILD_BUG_SQE_ELEM(48, __u64,  addr3);
 	BUILD_BUG_SQE_ELEM_SIZE(48, 0, cmd);
-	BUILD_BUG_SQE_ELEM(56, __u64,  __pad2);
+	BUILD_BUG_SQE_ELEM(58, __u16,  __pad2[0]);
 
 	BUILD_BUG_ON(sizeof(struct io_uring_files_update) !=
 		     sizeof(struct io_uring_rsrc_update));
@@ -3925,9 +3932,6 @@ static int __init io_uring_init(void)
 	BUILD_BUG_ON(offsetof(struct io_uring_buf, resv) !=
 		     offsetof(struct io_uring_buf_ring, tail));
 
-	/* should fit into one byte */
-	BUILD_BUG_ON(SQE_VALID_FLAGS >= (1 << 8));
-	BUILD_BUG_ON(SQE_COMMON_FLAGS >= (1 << 8));
 	BUILD_BUG_ON((SQE_VALID_FLAGS | SQE_COMMON_FLAGS) != SQE_VALID_FLAGS);
 
 	BUILD_BUG_ON(__REQ_F_LAST_BIT > 8 * sizeof_field(struct io_kiocb, flags));
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 535909a38e76..e86dea1173f3 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -200,7 +200,8 @@ int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
 
-	if (sqe->__pad1)
+	/* uring cmd doesn't support setting a personality */
+	if (sqe->__pad1 || req->flags & REQ_F_PERSONALITY)
 		return -EINVAL;
 
 	ioucmd->flags = READ_ONCE(sqe->uring_cmd_flags);

-- 
Jens Axboe

Re: [PATCH v2] io_uring: extend io_uring_sqe flags bits

[Ming Lei]

On Fri, Nov 01, 2024 at 09:15:28AM -0600, Jens Axboe wrote:
> In hindsight everything is clearer, but it probably should've been known
> that 8 bits of ->flags would run out sooner than later. Rather than
> gobble up the last bit for a random use case, add a bit that controls
> whether or not ->personality is used as a flags2 argument. If that is
> the case, then there's a new IOSQE2_PERSONALITY flag that tells io_uring
> which personality field to read.
> 
> While this isn't the prettiest, it does allow extending with 15 extra
> flags, and retains being able to use personality with any kind of
> command. The exception is uring cmd, where personality2 will overlap
> with the space set aside for SQE128. If they really need that, then that
> would have to be done via a uring cmd flag.
> 
> Signed-off-by: Jens Axboe <axboe@kernel.dk>

Reviewed-by: Ming Lei <ming.lei@redhat.com>

Thanks,
Ming