cmd/app: alternative merged template layout

This implements an optional, alternative template layout to accommodate
ZFS and equivalent setups where each template occupies a different
filesystem. In such a setup, the default, separate workdir is unusable
as overlayfs requires the workdir to reside on the same filesystem as
the writable upperdir. The "merge" build tag enables this alternative
behaviour.

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

1 files changed, 9 insertions, 10 deletions

diff --git a/cmd/app/lock.go b/cmd/app/lock.go
index 88068381..2a419ea1 100644
--- a/cmd/app/lock.go
+++ b/cmd/app/lock.go
@@ -8,7 +8,6 @@ import (
 	"strings"
 	"syscall"
 
-	"hakurei.app/check"
 	"hakurei.app/fhs"
 	"hakurei.app/hst"
 	"hakurei.app/internal/env"
@@ -24,15 +23,15 @@ func (e MutationConflictError) Error() string {
 }
 
 // informTemplate guards intention of a template or its derivatives.
-func informTemplate(base *check.Absolute, name string, mutable bool) (func() error, error) {
-	mu := lockedfile.MutexAt(base.Append("lock", name).String())
+func informTemplate(b *base, name string, mutable bool) (func() error, error) {
+	mu := lockedfile.MutexAt(b.append("lock", name).String())
 	if unlock, err := mu.Lock(); err != nil {
 		return nil, err
 	} else {
 		defer unlock()
 	}
 
-	marker := base.Append("lock", "."+name)
+	marker := b.append("lock", "."+name)
 	if p, err := os.ReadFile(marker.String()); err == nil {
 		if _, err = os.Stat(fhs.AbsProc.Append(string(p)).String()); err == nil {
 			return nil, MutationConflictError(p)
@@ -72,8 +71,8 @@ func informTemplate(base *check.Absolute, name string, mutable bool) (func() err
 
 		if !root.Target.Is(fhs.AbsRoot) ||
 			len(root.Lower) != 1 ||
-			!root.Lower[0].Is(base.Append("initial")) ||
-			!root.Upper.Is(base.Append("template", name)) ||
+			!root.Lower[0].Is(b.initial()) ||
+			!root.Upper.Is(b.template(name)) ||
 			root.Work != nil {
 			continue
 		}
@@ -102,12 +101,12 @@ func informTemplate(base *check.Absolute, name string, mutable bool) (func() err
 }
 
 // acquireTemplate obtains exclusivity of a template.
-func acquireTemplate(base *check.Absolute, name string) (remove func() error, err error) {
-	return informTemplate(base, name, true)
+func acquireTemplate(b *base, name string) (remove func() error, err error) {
+	return informTemplate(b, name, true)
 }
 
 // enterTemplate checks against exclusivity of a template.
-func enterTemplate(base *check.Absolute, name string) error {
-	_, err := informTemplate(base, name, false)
+func enterTemplate(b *base, name string) error {
+	_, err := informTemplate(b, name, false)
 	return err
 }