1 files changed, 80 insertions, 0 deletions
diff --git a/cmd/btrfs-rec/inspect_rebuildmappings.go b/cmd/btrfs-rec/inspect_rebuildmappings.go
new file mode 100644
index 0000000..c32bf53
--- /dev/null
+++ b/cmd/btrfs-rec/inspect_rebuildmappings.go
@@ -0,0 +1,80 @@
+// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/datawire/dlib/dlog"
+	"github.com/datawire/ocibuild/pkg/cliutil"
+	"github.com/spf13/cobra"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs"
+	"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"
+)
+
+func init() {
+	inspectors = append(inspectors, subcommand{
+		Command: cobra.Command{
+			Use:   "rebuild-mappings SCAN_RESULT.json",
+			Short: "Rebuild broken chunk/dev-extent/blockgroup trees",
+			Long: "" +
+				"The rebuilt information is printed as JSON on stdout, and can\n" +
+				"be loaded by the --mappings flag.\n" +
+				"\n" +
+				"This is very similar to `btrfs rescue chunk-recover`, but (1)\n" +
+				"does a better job, (2) is less buggy, and (3) doesn't actually\n" +
+				"write the info back to the filesystem; instead writing it\n" +
+				"out-of-band to stdout.",
+			Args: cliutil.WrapPositionalArgs(cobra.ExactArgs(1)),
+		},
+		RunE: func(fs *btrfs.FS, cmd *cobra.Command, args []string) error {
+			ctx := cmd.Context()
+
+			scanResultsBytes, err := os.ReadFile(args[0])
+			if err != nil {
+				return err
+			}
+			var scanResults map[btrfsvol.DeviceID]btrfsinspect.ScanOneDevResult
+			if err := json.Unmarshal(scanResultsBytes, &scanResults); err != nil {
+				return err
+			}
+
+			devices := fs.LV.PhysicalVolumes()
+			for _, devID := range maps.SortedKeys(scanResults) {
+				dev, ok := devices[devID]
+				if !ok {
+					return fmt.Errorf("device ID %v mentioned in %q is not part of the filesystem",
+						devID, args[0])
+				}
+				dlog.Infof(ctx, "Rebuilding mappings from results on device %v...",
+					dev.Name())
+				scanResults[devID].AddToLV(ctx, fs, dev)
+			}
+
+			dlog.Infof(ctx, "Writing reconstructed mappings to stdout...")
+			mappings := fs.LV.Mappings()
+			_, _ = io.WriteString(os.Stdout, "[\n")
+			for i, mapping := range mappings {
+				suffix := ","
+				if i == len(mappings)-1 {
+					suffix = ""
+				}
+				bs, err := json.Marshal(mapping)
+				if err != nil {
+					return err
+				}
+				fmt.Printf("  %s%s\n", bs, suffix)
+			}
+			_, _ = io.WriteString(os.Stdout, "]\n")
+			return nil
+		},
+	})
+}