1 files changed, 80 insertions, 0 deletions
diff --git a/lib/btrfsprogs/btrfsinspect/rebuildmappings/gaps.go b/lib/btrfsprogs/btrfsinspect/rebuildmappings/gaps.go
new file mode 100644
index 0000000..f5fb27a
--- /dev/null
+++ b/lib/btrfsprogs/btrfsinspect/rebuildmappings/gaps.go
@@ -0,0 +1,80 @@
+// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package rebuildmappings
+
+import (
+	"context"
+	"sort"
+
+	"golang.org/x/exp/constraints"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsitem"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfsprogs/btrfsinspect"
+	"git.lukeshu.com/btrfs-progs-ng/lib/maps"
+)
+
+type PhysicalGap struct {
+	Beg, End btrfsvol.PhysicalAddr
+}
+
+func ListPhysicalGaps(fs *btrfs.FS) map[btrfsvol.DeviceID][]PhysicalGap {
+	gaps := make(map[btrfsvol.DeviceID][]PhysicalGap)
+	pos := make(map[btrfsvol.DeviceID]btrfsvol.PhysicalAddr)
+	mappings := fs.LV.Mappings()
+	sort.Slice(mappings, func(i, j int) bool {
+		return mappings[i].PAddr.Cmp(mappings[j].PAddr) < 0
+	})
+	for _, mapping := range mappings {
+		if pos[mapping.PAddr.Dev] < mapping.PAddr.Addr {
+			gaps[mapping.PAddr.Dev] = append(gaps[mapping.PAddr.Dev], PhysicalGap{
+				Beg: pos[mapping.PAddr.Dev],
+				End: mapping.PAddr.Addr,
+			})
+		}
+		if pos[mapping.PAddr.Dev] < mapping.PAddr.Addr.Add(mapping.Size) {
+			pos[mapping.PAddr.Dev] = mapping.PAddr.Addr.Add(mapping.Size)
+		}
+	}
+	for devID, dev := range fs.LV.PhysicalVolumes() {
+		devSize := dev.Size()
+		if pos[devID] < devSize {
+			gaps[devID] = append(gaps[devID], PhysicalGap{
+				Beg: pos[devID],
+				End: devSize,
+			})
+		}
+	}
+	return gaps
+}
+
+func roundUp[T constraints.Integer](x, multiple T) T {
+	return ((x + multiple - 1) / multiple) * multiple
+}
+
+func WalkGaps(ctx context.Context,
+	sums btrfsinspect.AllSums, gaps map[btrfsvol.DeviceID][]PhysicalGap,
+	fn func(btrfsvol.DeviceID, btrfsinspect.SumRun[btrfsvol.PhysicalAddr]) error,
+) error {
+	for _, devID := range maps.SortedKeys(gaps) {
+		for _, gap := range gaps[devID] {
+			if err := ctx.Err(); err != nil {
+				return err
+			}
+			begAddr := roundUp(gap.Beg, btrfsitem.CSumBlockSize)
+			begOff := int(begAddr/btrfsitem.CSumBlockSize) * sums.Physical[devID].ChecksumSize
+			endOff := int(gap.End/btrfsitem.CSumBlockSize) * sums.Physical[devID].ChecksumSize
+			if err := fn(devID, btrfsinspect.SumRun[btrfsvol.PhysicalAddr]{
+				ChecksumSize: sums.Physical[devID].ChecksumSize,
+				Addr:         begAddr,
+				Sums:         sums.Physical[devID].Sums[begOff:endOff],
+			}); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}