From c910df75c332f605a26f9f9e09b04e98df054a5f Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Thu, 18 Aug 2022 04:17:09 -0600
Subject: add a dbgsums command

---
 cmd/btrfs-rec/inspect_dbgsums.go | 136 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 136 insertions(+)
 create mode 100644 cmd/btrfs-rec/inspect_dbgsums.go

(limited to 'cmd/btrfs-rec/inspect_dbgsums.go')

diff --git a/cmd/btrfs-rec/inspect_dbgsums.go b/cmd/btrfs-rec/inspect_dbgsums.go
new file mode 100644
index 0000000..e9fadce
--- /dev/null
+++ b/cmd/btrfs-rec/inspect_dbgsums.go
@@ -0,0 +1,136 @@
+// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+
+	"git.lukeshu.com/go/lowmemjson"
+	"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/btrfssum"
+	"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:  "dbgsums SCAN_RESULT.json",
+			Args: cliutil.WrapPositionalArgs(cobra.ExactArgs(1)),
+		},
+		RunE: func(fs *btrfs.FS, cmd *cobra.Command, args []string) (err error) {
+			maybeSetErr := func(_err error) {
+				if err == nil && _err != nil {
+					err = _err
+				}
+			}
+			ctx := cmd.Context()
+
+			dlog.Infof(ctx, "Reading %q...", args[0])
+			scanResults, err := func() (btrfsinspect.ScanDevicesResult, error) {
+				fh, err := os.Open(args[0])
+				if err != nil {
+					return nil, err
+				}
+				var scanResults btrfsinspect.ScanDevicesResult
+				if err := lowmemjson.DecodeThenEOF(fh, &scanResults); err != nil {
+					return nil, err
+				}
+				_ = fh.Close()
+				return scanResults, nil
+			}()
+			dlog.Infof(ctx, "... done reading %q", args[0])
+
+			dlog.Info(ctx, "Mapping the logical address space...")
+			type record struct {
+				Gen btrfs.Generation
+				Sum btrfssum.ShortSum
+			}
+			addrspace := make(map[btrfsvol.LogicalAddr]record)
+			var sumSize int
+			for _, devResults := range scanResults {
+				sumSize = devResults.Checksums.ChecksumSize
+				for _, sumItem := range devResults.FoundExtentCSums {
+					_ = sumItem.Sums.Walk(ctx, func(pos btrfsvol.LogicalAddr, sum btrfssum.ShortSum) error {
+						new := record{
+							Gen: sumItem.Generation,
+							Sum: sum,
+						}
+						if old, ok := addrspace[pos]; ok {
+							switch {
+							case old.Gen > new.Gen:
+								// do nothing
+							case old.Gen < new.Gen:
+								addrspace[pos] = new
+							case old.Gen == new.Gen:
+								if old != new {
+									dlog.Errorf(ctx, "mismatch of laddr=%v sum: %v != %v", pos, old, new)
+								}
+							}
+						} else {
+							addrspace[pos] = new
+						}
+						return nil
+					})
+				}
+			}
+			if len(addrspace) == 0 {
+				return fmt.Errorf("no checksums were found in the scan")
+			}
+			dlog.Info(ctx, "... done mapping")
+
+			dlog.Info(ctx, "Flattening the map ...")
+			var flattened btrfssum.SumRunWithGaps[btrfsvol.LogicalAddr]
+			var curAddr btrfsvol.LogicalAddr
+			var curSums strings.Builder
+			for _, laddr := range maps.SortedKeys(addrspace) {
+				if laddr != curAddr+(btrfsvol.LogicalAddr(curSums.Len()/sumSize)*btrfssum.BlockSize) {
+					if curSums.Len() > 0 {
+						flattened.Runs = append(flattened.Runs, btrfssum.SumRun[btrfsvol.LogicalAddr]{
+							ChecksumSize: sumSize,
+							Addr:         curAddr,
+							Sums:         btrfssum.ShortSum(curSums.String()),
+						})
+					}
+					curAddr = laddr
+					curSums.Reset()
+				}
+				curSums.WriteString(string(addrspace[laddr].Sum))
+			}
+			if curSums.Len() > 0 {
+				flattened.Runs = append(flattened.Runs, btrfssum.SumRun[btrfsvol.LogicalAddr]{
+					ChecksumSize: sumSize,
+					Addr:         curAddr,
+					Sums:         btrfssum.ShortSum(curSums.String()),
+				})
+			}
+			flattened.Addr = flattened.Runs[0].Addr
+			last := flattened.Runs[len(flattened.Runs)-1]
+			end := last.Addr.Add(last.Size())
+			flattened.Size = end.Sub(flattened.Addr)
+			dlog.Info(ctx, "... done flattening")
+
+			dlog.Info(ctx, "Writing addrspace sums to stdout...")
+			buffer := bufio.NewWriter(os.Stdout)
+			defer func() {
+				maybeSetErr(buffer.Flush())
+			}()
+			return lowmemjson.Encode(&lowmemjson.ReEncoder{
+				Out: buffer,
+
+				Indent:                "\t",
+				ForceTrailingNewlines: true,
+			}, flattened)
+		},
+	})
+}
-- 
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