From 3c3a883667390c2f03dffb3fdcb4fa4172cb23e6 Mon Sep 17 00:00:00 2001
From: Tobias Klauser <tklauser@distanz.ch>
Date: Mon, 22 May 2023 20:37:05 +0200
Subject: [PATCH] os: avoid second fcntl syscall in NewFile on unix
CL 494915 introduced an additional fcntl(F_GETFL) syscall to determine
whether the file is in append-only mode. The existing unix.IsNonblock
call also issues an fcntl(F_GETFL) syscall. The two can be combined and
both the append-only mode and the non-blocking flags can be determined
from that syscall's result.
Change-Id: I915589ed94e079f6abaa2fd0032ef01f78698f7f
Reviewed-on: https://go-review.googlesource.com/c/go/+/497075
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
---
src/os/file_unix.go | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/src/os/file_unix.go b/src/os/file_unix.go
index 25ce83bf9dc..a34de8333da 100644
--- a/src/os/file_unix.go
+++ b/src/os/file_unix.go
@@ -104,13 +104,15 @@ func (f *File) Fd() uintptr {
// constraints apply.
func NewFile(fd uintptr, name string) *File {
kind := kindNewFile
- if nb, err := unix.IsNonblock(int(fd)); err == nil && nb {
- kind = kindNonBlock
- }
- f := newFile(fd, name, kind)
+ appendMode := false
if flags, err := unix.Fcntl(int(fd), syscall.F_GETFL, 0); err == nil {
- f.appendMode = flags&syscall.O_APPEND != 0
+ if unix.HasNonblockFlag(flags) {
+ kind = kindNonBlock
+ }
+ appendMode = flags&syscall.O_APPEND != 0
}
+ f := newFile(fd, name, kind)
+ f.appendMode = appendMode
return f
}
--
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