[PATCH 02/16] 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 8ef8809b851f..439f95111b18 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9138,31 +9138,31 @@ 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