go.mod: github.com/moby/sys/mountinfo v0.6.0

full diff: https://github.com/moby/sys/compare/mountinfo/v0.5.0...mountinfo/v0.6.0

- Add MountedFast (Note: most users should keep using Mounted, which already
  incorporates all optimizations from MountedFast)

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

go.mod

@@ -41,7 +41,7 @@ require (
 	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/klauspost/compress v1.11.13
 	github.com/moby/locker v1.0.1
-	github.com/moby/sys/mountinfo v0.5.0
+	github.com/moby/sys/mountinfo v0.6.0
 	github.com/moby/sys/signal v0.6.0
 	github.com/moby/sys/symlink v0.2.0
 	github.com/opencontainers/go-digest v1.0.0

go.sum

@@ -474,8 +474,9 @@ github.com/moby/locker v1.0.1/go.mod h1:S7SDdo5zpBK84bzzVlKr2V0hz+7x9hWbYC/kq7oQ
 github.com/moby/spdystream v0.2.0 h1:cjW1zVyyoiM0T7b6UoySUFqzXMoqRckQtXwGPiBhOM8=
 github.com/moby/spdystream v0.2.0/go.mod h1:f7i0iNDQJ059oMTcWxx8MA/zKFIuD/lY+0GqbN2Wy8c=
 github.com/moby/sys/mountinfo v0.4.1/go.mod h1:rEr8tzG/lsIZHBtN/JjGG+LMYx9eXgW2JI+6q0qou+A=
-github.com/moby/sys/mountinfo v0.5.0 h1:2Ks8/r6lopsxWi9m58nlwjaeSzUX9iiL1vj5qB/9ObI=
 github.com/moby/sys/mountinfo v0.5.0/go.mod h1:3bMD3Rg+zkqx8MRYPi7Pyb0Ie97QEBmdxbhnCLlSvSU=
+github.com/moby/sys/mountinfo v0.6.0 h1:gUDhXQx58YNrpHlK4nSL+7y2pxFZkUcXqzFDKWdC0Oo=
+github.com/moby/sys/mountinfo v0.6.0/go.mod h1:3bMD3Rg+zkqx8MRYPi7Pyb0Ie97QEBmdxbhnCLlSvSU=
 github.com/moby/sys/signal v0.6.0 h1:aDpY94H8VlhTGa9sNYUFCFsMZIUh5wm0B6XkIoJj/iY=
 github.com/moby/sys/signal v0.6.0/go.mod h1:GQ6ObYZfqacOwTtlXvcmh9A26dVRul/hbOZn88Kg8Tg=
 github.com/moby/sys/symlink v0.2.0 h1:tk1rOM+Ljp0nFmfOIBtlV3rTDlWOwFRhjEeAhZB0nZc=

integration/client/go.sum

@@ -450,8 +450,9 @@ github.com/moby/locker v1.0.1 h1:fOXqR41zeveg4fFODix+1Ch4mj/gT0NE1XJbp/epuBg=
 github.com/moby/locker v1.0.1/go.mod h1:S7SDdo5zpBK84bzzVlKr2V0hz+7x9hWbYC/kq7oQppc=
 github.com/moby/spdystream v0.2.0/go.mod h1:f7i0iNDQJ059oMTcWxx8MA/zKFIuD/lY+0GqbN2Wy8c=
 github.com/moby/sys/mountinfo v0.4.1/go.mod h1:rEr8tzG/lsIZHBtN/JjGG+LMYx9eXgW2JI+6q0qou+A=
-github.com/moby/sys/mountinfo v0.5.0 h1:2Ks8/r6lopsxWi9m58nlwjaeSzUX9iiL1vj5qB/9ObI=
 github.com/moby/sys/mountinfo v0.5.0/go.mod h1:3bMD3Rg+zkqx8MRYPi7Pyb0Ie97QEBmdxbhnCLlSvSU=
+github.com/moby/sys/mountinfo v0.6.0 h1:gUDhXQx58YNrpHlK4nSL+7y2pxFZkUcXqzFDKWdC0Oo=
+github.com/moby/sys/mountinfo v0.6.0/go.mod h1:3bMD3Rg+zkqx8MRYPi7Pyb0Ie97QEBmdxbhnCLlSvSU=
 github.com/moby/sys/signal v0.6.0 h1:aDpY94H8VlhTGa9sNYUFCFsMZIUh5wm0B6XkIoJj/iY=
 github.com/moby/sys/signal v0.6.0/go.mod h1:GQ6ObYZfqacOwTtlXvcmh9A26dVRul/hbOZn88Kg8Tg=
 github.com/moby/sys/symlink v0.2.0/go.mod h1:7uZVF2dqJjG/NsClqul95CqKOBRQyYSNnJ6BMgR/gFs=

vendor/github.com/moby/sys/mountinfo/mounted_linux.go

@@ -7,6 +7,34 @@ import (
 	"golang.org/x/sys/unix"
 )
 
+// MountedFast is a method of detecting a mount point without reading
+// mountinfo from procfs. A caller can only trust the result if no error
+// and sure == true are returned. Otherwise, other methods (e.g. parsing
+// /proc/mounts) have to be used. If unsure, use Mounted instead (which
+// uses MountedFast, but falls back to parsing mountinfo if needed).
+//
+// If a non-existent path is specified, an appropriate error is returned.
+// In case the caller is not interested in this particular error, it should
+// be handled separately using e.g. errors.Is(err, os.ErrNotExist).
+//
+// This function is only available on Linux. When available (since kernel
+// v5.6), openat2(2) syscall is used to reliably detect all mounts. Otherwise,
+// the implementation falls back to using stat(2), which can reliably detect
+// normal (but not bind) mounts.
+func MountedFast(path string) (mounted, sure bool, err error) {
+	// Root is always mounted.
+	if path == string(os.PathSeparator) {
+		return true, true, nil
+	}
+
+	path, err = normalizePath(path)
+	if err != nil {
+		return false, false, err
+	}
+	mounted, sure, err = mountedFast(path)
+	return
+}
+
 // mountedByOpenat2 is a method of detecting a mount that works for all kinds
 // of mounts (incl. bind mounts), but requires a recent (v5.6+) linux kernel.
 func mountedByOpenat2(path string) (bool, error) {
@@ -34,24 +62,40 @@ func mountedByOpenat2(path string) (bool, error) {
 	return false, &os.PathError{Op: "openat2", Path: path, Err: err}
 }
 
-func mounted(path string) (bool, error) {
-	path, err := normalizePath(path)
-	if err != nil {
-		return false, err
+// mountedFast is similar to MountedFast, except it expects a normalized path.
+func mountedFast(path string) (mounted, sure bool, err error) {
+	// Root is always mounted.
+	if path == string(os.PathSeparator) {
+		return true, true, nil
 	}
+
 	// Try a fast path, using openat2() with RESOLVE_NO_XDEV.
-	mounted, err := mountedByOpenat2(path)
+	mounted, err = mountedByOpenat2(path)
 	if err == nil {
-		return mounted, nil
+		return mounted, true, nil
 	}
+
 	// Another fast path: compare st.st_dev fields.
 	mounted, err = mountedByStat(path)
 	// This does not work for bind mounts, so false negative
 	// is possible, therefore only trust if return is true.
 	if mounted && err == nil {
+		return true, true, nil
+	}
+
+	return
+}
+
+func mounted(path string) (bool, error) {
+	path, err := normalizePath(path)
+	if err != nil {
+		return false, err
+	}
+	mounted, sure, err := mountedFast(path)
+	if sure && err == nil {
 		return mounted, nil
 	}
 
-	// Fallback to parsing mountinfo
+	// Fallback to parsing mountinfo.
 	return mountedByMountinfo(path)
 }

vendor/github.com/moby/sys/mountinfo/mountinfo.go

@@ -13,9 +13,9 @@ func GetMounts(f FilterFunc) ([]*Info, error) {
 // Mounted determines if a specified path is a mount point. In case of any
 // error, false (and an error) is returned.
 //
-// The non-existent path returns an error. If a caller is not interested
-// in this particular error, it should handle it separately using e.g.
-// errors.Is(err, os.ErrNotExist).
+// If a non-existent path is specified, an appropriate error is returned.
+// In case the caller is not interested in this particular error, it should
+// be handled separately using e.g. errors.Is(err, os.ErrNotExist).
 func Mounted(path string) (bool, error) {
 	// root is always mounted
 	if path == string(os.PathSeparator) {

vendor/modules.txt

@@ -284,7 +284,7 @@ github.com/moby/locker
 # github.com/moby/spdystream v0.2.0
 github.com/moby/spdystream
 github.com/moby/spdystream/spdy
-# github.com/moby/sys/mountinfo v0.5.0
+# github.com/moby/sys/mountinfo v0.6.0
 ## explicit
 github.com/moby/sys/mountinfo
 # github.com/moby/sys/signal v0.6.0