internal/system: skip superfluous chmod

A successful chmod clobbers acl mask, breaking the fast path. This
change also fixes the ACL race.

Signed-off-by: Ophestra <cat@gensokyo.uk>

1 files changed, 31 insertions, 9 deletions

diff --git a/internal/system/mkdir.go b/internal/system/mkdir.go
index 81b89d58..ecbfc876 100644
--- a/internal/system/mkdir.go
+++ b/internal/system/mkdir.go
@@ -4,21 +4,33 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"syscall"
 
 	"hakurei.app/check"
 	"hakurei.app/hst"
 )
 
 // Ensure ensures the existence of a directory.
-func (sys *I) Ensure(name *check.Absolute, perm os.FileMode) *I {
-	sys.ops = append(sys.ops, &mkdirOp{User, name.String(), perm, false})
+func (sys *I) Ensure(name *check.Absolute, perm os.FileMode, skipChmod bool) *I {
+	sys.ops = append(sys.ops, &mkdirOp{
+		et:        User,
+		path:      name.String(),
+		perm:      perm,
+		skipChmod: skipChmod,
+	})
 	return sys
 }
 
 // Ephemeral ensures the existence of a directory until its [hst.Enablements] is
 // no longer satisfied.
-func (sys *I) Ephemeral(et hst.Enablements, name *check.Absolute, perm os.FileMode) *I {
-	sys.ops = append(sys.ops, &mkdirOp{et, name.String(), perm, true})
+func (sys *I) Ephemeral(et hst.Enablements, name *check.Absolute, perm os.FileMode, skipChmod bool) *I {
+	sys.ops = append(sys.ops, &mkdirOp{
+		et:        et,
+		path:      name.String(),
+		perm:      perm,
+		ephemeral: true,
+		skipChmod: skipChmod,
+	})
 	return sys
 }
 
@@ -28,6 +40,7 @@ type mkdirOp struct {
 	path      string
 	perm      os.FileMode
 	ephemeral bool
+	skipChmod bool
 }
 
 func (m *mkdirOp) Type() hst.Enablements { return m.et }
@@ -35,12 +48,21 @@ func (m *mkdirOp) Type() hst.Enablements { return m.et }
 func (m *mkdirOp) apply(sys *I) error {
 	sys.msg.Verbose("ensuring directory", m)
 
-	if err := sys.mkdir(m.path, m.perm); err != nil {
-		if !errors.Is(err, os.ErrExist) {
-			return newOpError("mkdir", err, false)
+	if fi, err := sys.stat(m.path); err == nil {
+		if !fi.IsDir() {
+			return newOpError("mkdir", syscall.ENOTDIR, false)
+		}
+		if !m.skipChmod && fi.Mode().Perm() != m.perm {
+			// directory exists, ensure mode
+			return newOpError("mkdir", sys.chmod(m.path, m.perm), false)
 		}
-		// directory exists, ensure mode
-		return newOpError("mkdir", sys.chmod(m.path, m.perm), false)
+		return nil
+	} else if !errors.Is(err, os.ErrNotExist) {
+		return newOpError("mkdir", err, false)
+	}
+
+	if err := sys.mkdir(m.path, m.perm); err != nil {
+		return newOpError("mkdir", err, false)
 	} else {
 		return nil
 	}