Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

os: RemoveAll: pass the O_NONBLOCK flag to openat(2) instead of making an extra fcntl(2) call #56843

Closed
aktau opened this issue Nov 18, 2022 · 2 comments
Labels
FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
Milestone

Comments

@aktau
Copy link
Contributor

aktau commented Nov 18, 2022

What version of Go are you using (go version)?

1.20 (pre-prelease, a813be8)

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GOARCH="amd64"

What did you do?

I called os.RemoveAll and a colleague saw syscall.fcntl in the resulting profile:

image

This colleague said that we could also pass O_NONBLOCK to the open(2) syscall.

Reference: https://cs.opensource.google/go/go/+/master:src/os/removeall_at.go;l=174,191;drc=3e5c2c155645ebaed62e4481430c455045b0fff5

Something like:

// openFdAt opens path relative to the directory in fd.
// Other than that this should act like openFileNolog.
// This acts like openFileNolog rather than OpenFile because
// we are going to (try to) remove the file.
// The contents of this file are not relevant for test caching.
func openFdAt(dirfd int, name string) (*File, error) {
	var r int
	for {
		var e error
-		r, e = unix.Openat(dirfd, name, O_RDONLY|syscall.O_CLOEXEC, 0)
+		r, e = unix.Openat(dirfd, name, O_RDONLY|syscall.O_CLOEXEC|O_NONBLOCK, 0)
 
		if e == nil {
			break
		}

		// See comment in openFileNolog.
		if e == syscall.EINTR {
			continue
		}

		return nil, e
	}

	if !supportsCloseOnExec {
		syscall.CloseOnExec(r)
	}

-	return newFile(uintptr(r), name, kindOpenFile), nil
+	return newFile(uintptr(r), name, kindNonBlocking), nil
}

There's probably a good reason why things are the way they are. But I couldn't think of any.

@ianlancetaylor ianlancetaylor changed the title os.RemoveAll: pass the O_NONBLOCK flag to openat(2) instead of making an extra fcntl(2) call os: RemoveAll: pass the O_NONBLOCK flag to openat(2) instead of making an extra fcntl(2) call Nov 18, 2022
@gopherbot
Copy link

Change https://go.dev/cl/451997 mentions this issue: os: don't try to put directory into non-blocking mode

@ianlancetaylor
Copy link
Contributor

In this case we know that the file is a directory, and directories aren't usually supported by the poller anyhow. So rather than open in non-blocking mode, which is kind of meaningless for a directory, we can tell newFile to skip the change to non-blocking mode. I sent https://go.dev/cl/451997 for this. Not sure it's worth doing at this stage of the release cycle, though.

@seankhliao seankhliao added the NeedsFix The path to resolution is known, but the work has not been done. label Nov 19, 2022
@seankhliao seankhliao added this to the Backlog milestone Nov 19, 2022
@dmitshur dmitshur modified the milestones: Backlog, Go1.21 Feb 27, 2023
@golang golang locked and limited conversation to collaborators Feb 27, 2024
Sign up for free to subscribe to this conversation on GitHub. Already have an account? Sign in.
Labels
FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
Projects
None yet
Development

No branches or pull requests

5 participants