io_uring: optimise io_import_iovec nonblock passing

First, change IO_URING_F_NONBLOCK to take sign bit of the int, so
checking for it can be turned into test + sign-based-jump, makes the
binary smaller and may be faster.

Then, instead of passing need_lock boolean into io_import_iovec() just
give it issue_flags, which is already stored somewhere. Saves some space
on stack, a couple of test + cmov operations and other conversions.

note: we still leave
force_nonblock = issue_flags & IO_URING_F_NONBLOCK
variable, but it's optimised out by the compiler into testing
issue_flags directly.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/ee96547e692f6c975c229cd82fc721679571a734.1634144845.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -198,8 +198,9 @@ struct io_rings {
 };
 
 enum io_uring_cmd_flags {
-	IO_URING_F_NONBLOCK		= 1,
-	IO_URING_F_COMPLETE_DEFER	= 2,
+	IO_URING_F_COMPLETE_DEFER	= 1,
+	/* int's last bit, sign checks are usually faster than a bit test */
+	IO_URING_F_NONBLOCK		= INT_MIN,
 };
 
 struct io_mapped_ubuf {
@@ -3037,10 +3038,11 @@ static void io_ring_submit_lock(struct io_ring_ctx *ctx, bool needs_lock)
 }
 
 static struct io_buffer *io_buffer_select(struct io_kiocb *req, size_t *len,
-					  int bgid, bool needs_lock)
+					  int bgid, unsigned int issue_flags)
 {
 	struct io_buffer *kbuf = req->kbuf;
 	struct io_buffer *head;
+	bool needs_lock = !(issue_flags & IO_URING_F_NONBLOCK);
 
 	if (req->flags & REQ_F_BUFFER_SELECTED)
 		return kbuf;
@@ -3072,13 +3074,13 @@ static struct io_buffer *io_buffer_select(struct io_kiocb *req, size_t *len,
 }
 
 static void __user *io_rw_buffer_select(struct io_kiocb *req, size_t *len,
-					bool needs_lock)
+					unsigned int issue_flags)
 {
 	struct io_buffer *kbuf;
 	u16 bgid;
 
 	bgid = req->buf_index;
-	kbuf = io_buffer_select(req, len, bgid, needs_lock);
+	kbuf = io_buffer_select(req, len, bgid, issue_flags);
 	if (IS_ERR(kbuf))
 		return kbuf;
 	return u64_to_user_ptr(kbuf->addr);
@@ -3086,7 +3088,7 @@ static void __user *io_rw_buffer_select(struct io_kiocb *req, size_t *len,
 
 #ifdef CONFIG_COMPAT
 static ssize_t io_compat_import(struct io_kiocb *req, struct iovec *iov,
-				bool needs_lock)
+				unsigned int issue_flags)
 {
 	struct compat_iovec __user *uiov;
 	compat_ssize_t clen;
@@ -3102,7 +3104,7 @@ static ssize_t io_compat_import(struct io_kiocb *req, struct iovec *iov,
 		return -EINVAL;
 
 	len = clen;
-	buf = io_rw_buffer_select(req, &len, needs_lock);
+	buf = io_rw_buffer_select(req, &len, issue_flags);
 	if (IS_ERR(buf))
 		return PTR_ERR(buf);
 	iov[0].iov_base = buf;
@@ -3112,7 +3114,7 @@ static ssize_t io_compat_import(struct io_kiocb *req, struct iovec *iov,
 #endif
 
 static ssize_t __io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
-				      bool needs_lock)
+				      unsigned int issue_flags)
 {
 	struct iovec __user *uiov = u64_to_user_ptr(req->rw.addr);
 	void __user *buf;
@@ -3124,7 +3126,7 @@ static ssize_t __io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
 	len = iov[0].iov_len;
 	if (len < 0)
 		return -EINVAL;
-	buf = io_rw_buffer_select(req, &len, needs_lock);
+	buf = io_rw_buffer_select(req, &len, issue_flags);
 	if (IS_ERR(buf))
 		return PTR_ERR(buf);
 	iov[0].iov_base = buf;
@@ -3133,7 +3135,7 @@ static ssize_t __io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
 }
 
 static ssize_t io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
-				    bool needs_lock)
+				    unsigned int issue_flags)
 {
 	if (req->flags & REQ_F_BUFFER_SELECTED) {
 		struct io_buffer *kbuf = req->kbuf;
@@ -3147,14 +3149,14 @@ static ssize_t io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
 
 #ifdef CONFIG_COMPAT
 	if (req->ctx->compat)
-		return io_compat_import(req, iov, needs_lock);
+		return io_compat_import(req, iov, issue_flags);
 #endif
 
-	return __io_iov_buffer_select(req, iov, needs_lock);
+	return __io_iov_buffer_select(req, iov, issue_flags);
 }
 
 static int io_import_iovec(int rw, struct io_kiocb *req, struct iovec **iovec,
-			   struct iov_iter *iter, bool needs_lock)
+			   struct iov_iter *iter, unsigned int issue_flags)
 {
 	void __user *buf = u64_to_user_ptr(req->rw.addr);
 	size_t sqe_len = req->rw.len;
@@ -3172,7 +3174,7 @@ static int io_import_iovec(int rw, struct io_kiocb *req, struct iovec **iovec,
 
 	if (opcode == IORING_OP_READ || opcode == IORING_OP_WRITE) {
 		if (req->flags & REQ_F_BUFFER_SELECT) {
-			buf = io_rw_buffer_select(req, &sqe_len, needs_lock);
+			buf = io_rw_buffer_select(req, &sqe_len, issue_flags);
 			if (IS_ERR(buf))
 				return PTR_ERR(buf);
 			req->rw.len = sqe_len;
@@ -3184,7 +3186,7 @@ static int io_import_iovec(int rw, struct io_kiocb *req, struct iovec **iovec,
 	}
 
 	if (req->flags & REQ_F_BUFFER_SELECT) {
-		ret = io_iov_buffer_select(req, *iovec, needs_lock);
+		ret = io_iov_buffer_select(req, *iovec, issue_flags);
 		if (!ret)
 			iov_iter_init(iter, rw, *iovec, 1, (*iovec)->iov_len);
 		*iovec = NULL;
@@ -3323,7 +3325,8 @@ static inline int io_rw_prep_async(struct io_kiocb *req, int rw)
 	struct iovec *iov = iorw->s.fast_iov;
 	int ret;
 
-	ret = io_import_iovec(rw, req, &iov, &iorw->s.iter, false);
+	/* submission path, ->uring_lock should already be taken */
+	ret = io_import_iovec(rw, req, &iov, &iorw->s.iter, IO_URING_F_NONBLOCK);
 	if (unlikely(ret < 0))
 		return ret;
 
@@ -3451,7 +3454,7 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
 	} else {
 		s = &__s;
 		iovec = s->fast_iov;
-		ret = io_import_iovec(READ, req, &iovec, &s->iter, !force_nonblock);
+		ret = io_import_iovec(READ, req, &iovec, &s->iter, issue_flags);
 		if (ret < 0)
 			return ret;
 
@@ -3579,7 +3582,7 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
 	} else {
 		s = &__s;
 		iovec = s->fast_iov;
-		ret = io_import_iovec(WRITE, req, &iovec, &s->iter, !force_nonblock);
+		ret = io_import_iovec(WRITE, req, &iovec, &s->iter, issue_flags);
 		if (ret < 0)
 			return ret;
 		iov_iter_save_state(&s->iter, &s->iter_state);
@@ -4902,11 +4905,11 @@ static int io_recvmsg_copy_hdr(struct io_kiocb *req,
 }
 
 static struct io_buffer *io_recv_buffer_select(struct io_kiocb *req,
-					       bool needs_lock)
+					       unsigned int issue_flags)
 {
 	struct io_sr_msg *sr = &req->sr_msg;
 
-	return io_buffer_select(req, &sr->len, sr->bgid, needs_lock);
+	return io_buffer_select(req, &sr->len, sr->bgid, issue_flags);
 }
 
 static inline unsigned int io_put_recv_kbuf(struct io_kiocb *req)
@@ -4969,7 +4972,7 @@ static int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 	}
 
 	if (req->flags & REQ_F_BUFFER_SELECT) {
-		kbuf = io_recv_buffer_select(req, !force_nonblock);
+		kbuf = io_recv_buffer_select(req, issue_flags);
 		if (IS_ERR(kbuf))
 			return PTR_ERR(kbuf);
 		kmsg->fast_iov[0].iov_base = u64_to_user_ptr(kbuf->addr);
@@ -5021,7 +5024,7 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 		return -ENOTSOCK;
 
 	if (req->flags & REQ_F_BUFFER_SELECT) {
-		kbuf = io_recv_buffer_select(req, !force_nonblock);
+		kbuf = io_recv_buffer_select(req, issue_flags);
 		if (IS_ERR(kbuf))
 			return PTR_ERR(kbuf);
 		buf = u64_to_user_ptr(kbuf->addr);