From 0057ac685125aea5cf06dfd8eeaa7c7d52e64dfa Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Fri, 15 Jul 2022 14:36:47 -0600
Subject: wip

---
 lib/btrfs/btrfsvol/lvm.go | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

(limited to 'lib/btrfs/btrfsvol')

diff --git a/lib/btrfs/btrfsvol/lvm.go b/lib/btrfs/btrfsvol/lvm.go
index 9b16e10..8003466 100644
--- a/lib/btrfs/btrfsvol/lvm.go
+++ b/lib/btrfs/btrfsvol/lvm.go
@@ -6,6 +6,7 @@ package btrfsvol
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"os"
 	"reflect"
@@ -117,7 +118,13 @@ type Mapping struct {
 	Flags      containers.Optional[BlockGroupFlags] `json:",omitempty"`
 }
 
+func (lv *LogicalVolume[PhysicalVolume]) CouldAddMapping(m Mapping) bool {
+	return lv.addMapping(m, true) == nil
+}
 func (lv *LogicalVolume[PhysicalVolume]) AddMapping(m Mapping) error {
+	return lv.addMapping(m, false)
+}
+func (lv *LogicalVolume[PhysicalVolume]) addMapping(m Mapping, dryRun bool) error {
 	lv.init()
 	// sanity check
 	if _, haveDev := lv.id2pv[m.PAddr.Dev]; !haveDev {
@@ -154,6 +161,10 @@ func (lv *LogicalVolume[PhysicalVolume]) AddMapping(m Mapping) error {
 		return fmt.Errorf("(%p).AddMapping: %w", lv, err)
 	}
 
+	if dryRun {
+		return nil
+	}
+
 	// optimize
 	if len(logicalOverlaps) == 1 && reflect.DeepEqual(newChunk, logicalOverlaps[0]) &&
 		len(physicalOverlaps) == 1 && reflect.DeepEqual(newExt, physicalOverlaps[0]) {
@@ -301,10 +312,12 @@ func (lv *LogicalVolume[PhysicalVolume]) ReadAt(dat []byte, laddr LogicalAddr) (
 	return done, nil
 }
 
+var ErrCouldNotMap = errors.New("could not map logical address")
+
 func (lv *LogicalVolume[PhysicalVolume]) maybeShortReadAt(dat []byte, laddr LogicalAddr) (int, error) {
 	paddrs, maxlen := lv.Resolve(laddr)
 	if len(paddrs) == 0 {
-		return 0, fmt.Errorf("read: could not map logical address %v", laddr)
+		return 0, fmt.Errorf("read: %w %v", ErrCouldNotMap, laddr)
 	}
 	if AddrDelta(len(dat)) > maxlen {
 		dat = dat[:maxlen]
@@ -346,7 +359,7 @@ func (lv *LogicalVolume[PhysicalVolume]) WriteAt(dat []byte, laddr LogicalAddr)
 func (lv *LogicalVolume[PhysicalVolume]) maybeShortWriteAt(dat []byte, laddr LogicalAddr) (int, error) {
 	paddrs, maxlen := lv.Resolve(laddr)
 	if len(paddrs) == 0 {
-		return 0, fmt.Errorf("write: could not map logical address %v", laddr)
+		return 0, fmt.Errorf("write: %w %v", ErrCouldNotMap, laddr)
 	}
 	if AddrDelta(len(dat)) > maxlen {
 		dat = dat[:maxlen]
-- 
cgit v1.2.3-54-g00ecf