[PATCH 02/11] io_uring: optimise io_uring_enter()

[Pavel Begunkov <asml.silence@gmail.com>]

Add unlikely annotations, because my compiler pretty much mispredicts
every first check, and apart jumping around in the fast path, it also
generates extra instructions, like in advance setting ret value.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 36d0bc506be4..9175ab937e34 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9001,31 +9001,31 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 		size_t, argsz)
 {
 	struct io_ring_ctx *ctx;
-	long ret = -EBADF;
 	int submitted = 0;
 	struct fd f;
+	long ret;
 
 	io_run_task_work();
 
-	if (flags & ~(IORING_ENTER_GETEVENTS | IORING_ENTER_SQ_WAKEUP |
-			IORING_ENTER_SQ_WAIT | IORING_ENTER_EXT_ARG))
+	if (unlikely(flags & ~(IORING_ENTER_GETEVENTS | IORING_ENTER_SQ_WAKEUP |
+			       IORING_ENTER_SQ_WAIT | IORING_ENTER_EXT_ARG)))
 		return -EINVAL;
 
 	f = fdget(fd);
-	if (!f.file)
+	if (unlikely(!f.file))
 		return -EBADF;
 
 	ret = -EOPNOTSUPP;
-	if (f.file->f_op != &io_uring_fops)
+	if (unlikely(f.file->f_op != &io_uring_fops))
 		goto out_fput;
 
 	ret = -ENXIO;
 	ctx = f.file->private_data;
-	if (!percpu_ref_tryget(&ctx->refs))
+	if (unlikely(!percpu_ref_tryget(&ctx->refs)))
 		goto out_fput;
 
 	ret = -EBADFD;
-	if (ctx->flags & IORING_SETUP_R_DISABLED)
+	if (unlikely(ctx->flags & IORING_SETUP_R_DISABLED))
 		goto out;
 
 	/*
-- 
2.24.0