implement scan-for-nodes command

1 files changed, 70 insertions, 0 deletions

diff --git a/cmd/btrfs-rec/inspect_scanfornodes.go b/cmd/btrfs-rec/inspect_scanfornodes.go
new file mode 100644
index 0000000..3eee46c
--- /dev/null
+++ b/cmd/btrfs-rec/inspect_scanfornodes.go
@@ -0,0 +1,70 @@
+// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"os"
+	"sync"
+
+	"github.com/datawire/dlib/dgroup"
+	"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"
+)
+
+func init() {
+	inspectors = append(inspectors, subcommand{
+		Command: cobra.Command{
+			Use:   "scan-for-nodes",
+			Short: "Scan devices for (potentially lost) nodes",
+			Long: "" +
+				"The found information is printed as JSON on stdout.\n" +
+				"\n" +
+				"This information is mostly useful for rebuilding a broken\n" +
+				"chunk/dev-extent/blockgroup trees, but can also have some\n" +
+				"minimal utility in repairing other trees.\n" +
+				"\n" +
+				"This is very similar the initial scan done by\n" +
+				"`btrfs rescue chunk-recover`.  Like `btrfs rescue chunk-recover`,\n" +
+				"this is likely probably slow because it reads the entirety of\n" +
+				"each device.",
+			Args: cliutil.WrapPositionalArgs(cobra.NoArgs),
+		},
+		RunE: func(fs *btrfs.FS, cmd *cobra.Command, _ []string) error {
+			ctx := cmd.Context()
+
+			var resultsMu sync.Mutex
+			results := make(map[btrfsvol.DeviceID]btrfsinspect.ScanOneDevResult)
+			grp := dgroup.NewGroup(ctx, dgroup.GroupConfig{})
+			for _, dev := range fs.LV.PhysicalVolumes() {
+				grp.Go(dev.Name(), func(ctx context.Context) error {
+					superblock, err := dev.Superblock()
+					if err != nil {
+						return err
+					}
+					dlog.Infof(ctx, "dev[%q] Scanning for unreachable nodes...", dev.Name())
+					devResult, err := btrfsinspect.ScanOneDev(ctx, dev, *superblock)
+					dlog.Infof(ctx, "dev[%q] Finished scanning", dev.Name())
+					resultsMu.Lock()
+					results[superblock.DevItem.DevID] = devResult
+					resultsMu.Unlock()
+					return err
+				})
+			}
+			if err := grp.Wait(); err != nil {
+				return err
+			}
+
+			dlog.Info(ctx, "Serializing results...")
+			return json.NewEncoder(os.Stdout).Encode(results)
+		},
+	})
+}