implement scan-for-extents

2 files changed, 217 insertions, 0 deletions

diff --git a/cmd/btrfs-rec/inspect_scanforextents.go b/cmd/btrfs-rec/inspect_scanforextents.go
new file mode 100644
index 0000000..98f7129
--- /dev/null
+++ b/cmd/btrfs-rec/inspect_scanforextents.go
@@ -0,0 +1,216 @@
+// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package main
+
+import (
+	"bufio"
+	"context"
+	"encoding/json"
+	"os"
+	"runtime"
+	"sort"
+	"sync"
+
+	"github.com/datawire/dlib/dgroup"
+	"github.com/datawire/dlib/dlog"
+	"github.com/datawire/ocibuild/pkg/cliutil"
+	"github.com/spf13/cobra"
+	"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/btrfsutil"
+	"git.lukeshu.com/btrfs-progs-ng/lib/maps"
+)
+
+const csumBlockSize = 4 * 1024
+
+type shortSum string
+
+func init() {
+	inspectors = append(inspectors, subcommand{
+		Command: cobra.Command{
+			Use:  "scan-for-extents",
+			Args: cliutil.WrapPositionalArgs(cobra.NoArgs),
+		},
+		RunE: func(fs *btrfs.FS, cmd *cobra.Command, _ []string) error {
+			ctx := cmd.Context()
+
+			dlog.Info(ctx, "Reading checksum tree...")
+			sum2laddrs := listUnmappedCheckummedExtents(ctx, fs)
+			dlog.Info(ctx, "... done reading checksum tree")
+
+			devs := fs.LV.PhysicalVolumes()
+			gaps := listPhysicalGaps(fs)
+
+			var mu sync.Mutex
+			sum2paddrs := make(map[shortSum][]btrfsvol.QualifiedPhysicalAddr)
+			grp := dgroup.NewGroup(ctx, dgroup.GroupConfig{})
+			for devID := range gaps {
+				devGaps := gaps[devID]
+				dev := devs[devID]
+				grp.Go(dev.Name(), func(ctx context.Context) error {
+					devSum2paddrs, err := scanOneDev(ctx, dev, devGaps, sum2laddrs)
+					mu.Lock()
+					for sum, paddrs := range devSum2paddrs {
+						sum2paddrs[sum] = append(sum2paddrs[sum], paddrs...)
+					}
+					mu.Unlock()
+					return err
+				})
+			}
+			if err := grp.Wait(); err != nil {
+				return err
+			}
+
+			dlog.Info(ctx, "Writing scan results to stdout...")
+			out := bufio.NewWriter(os.Stdout)
+			_, _ = out.WriteString("{")
+			for i, sum := range maps.SortedKeys(sum2laddrs) {
+				_, _ = out.WriteString("\n  ")
+
+				kBytes, _ := json.Marshal(sum)
+				_, _ = out.Write(kBytes)
+
+				_, _ = out.WriteString(": ")
+
+				vBytes, _ := json.Marshal(map[string]interface{}{
+					"laddrs": sum2laddrs[sum],
+					"paddrs": sum2paddrs[sum],
+				})
+				_, _ = out.Write(vBytes)
+
+				if i != len(sum2laddrs)-1 {
+					_, _ = out.WriteString(",")
+				}
+			}
+			_, _ = out.WriteString("\n}")
+			out.Flush()
+
+			return nil
+		},
+	})
+}
+
+func listUnmappedCheckummedExtents(ctx context.Context, fs *btrfs.FS) map[shortSum][]btrfsvol.LogicalAddr {
+	sum2laddrs := make(map[shortSum][]btrfsvol.LogicalAddr)
+	btrfsutil.NewBrokenTrees(ctx, fs).TreeWalk(ctx, btrfs.CSUM_TREE_OBJECTID,
+		func(err *btrfs.TreeError) {
+			dlog.Error(ctx, err)
+		},
+		btrfs.TreeWalkHandler{
+			Item: func(path btrfs.TreePath, item btrfs.Item) error {
+				if item.Key.ItemType != btrfsitem.EXTENT_CSUM_KEY {
+					return nil
+				}
+				body := item.Body.(btrfsitem.ExtentCSum)
+				for i, _sum := range body.Sums {
+					laddr := btrfsvol.LogicalAddr(item.Key.Offset) + btrfsvol.LogicalAddr(i*csumBlockSize)
+					if paddrs, _ := fs.LV.Resolve(laddr); len(paddrs) > 0 {
+						continue
+					}
+					sum := shortSum(_sum[:body.ChecksumSize])
+					sum2laddrs[sum] = append(sum2laddrs[sum], laddr)
+				}
+				return nil
+			},
+		},
+	)
+	return sum2laddrs
+}
+
+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 scanOneDev[T any](ctx context.Context, dev *btrfs.Device, gaps []physicalGap, sumsToScanFor map[shortSum]T) (map[shortSum][]btrfsvol.QualifiedPhysicalAddr, error) {
+	dlog.Infof(ctx, "... dev[%q] Scanning for extents...", dev.Name())
+	sb, err := dev.Superblock()
+	if err != nil {
+		return nil, err
+	}
+
+	devSize := dev.Size()
+	lastProgress := -1
+	progress := func(pos btrfsvol.PhysicalAddr) {
+		pct := int(100 * float64(pos) / float64(devSize))
+		if pct != lastProgress || pos == devSize {
+			dlog.Infof(ctx, "... dev[%q] scanned %v%%",
+				dev.Name(), pct)
+			lastProgress = pct
+			if pct%5 == 0 {
+				runtime.GC()
+			}
+		}
+	}
+
+	sumSize := sb.ChecksumType.Size()
+
+	var buf [csumBlockSize]byte
+	devSum2paddrs := make(map[shortSum][]btrfsvol.QualifiedPhysicalAddr)
+	for _, gap := range gaps {
+		for paddr := roundUp(gap.Beg, csumBlockSize); paddr+csumBlockSize <= gap.End; paddr += csumBlockSize {
+			progress(paddr)
+			if err := ctx.Err(); err != nil {
+				return nil, err
+			}
+			_, err := dev.ReadAt(buf[:], paddr)
+			if err != nil {
+				dlog.Error(ctx, err)
+				continue
+			}
+			_sum, err := sb.ChecksumType.Sum(buf[:])
+			if err != nil {
+				dlog.Error(ctx, err)
+				continue
+			}
+			sum := shortSum(_sum[:sumSize])
+			if _, interesting := sumsToScanFor[sum]; !interesting {
+				continue
+			}
+			devSum2paddrs[sum] = append(devSum2paddrs[sum], btrfsvol.QualifiedPhysicalAddr{
+				Dev:  sb.DevItem.DevID,
+				Addr: paddr,
+			})
+		}
+	}
+	progress(devSize)
+	return devSum2paddrs, nil
+}
diff --git a/cmd/btrfs-rec/inspect_scanfornodes.go b/cmd/btrfs-rec/inspect_scanfornodes.go
index 9dbc3a5..8ddf1fd 100644
--- a/cmd/btrfs-rec/inspect_scanfornodes.go
+++ b/cmd/btrfs-rec/inspect_scanfornodes.go
@@ -46,6 +46,7 @@ func init() {
 			results := make(map[btrfsvol.DeviceID]btrfsinspect.ScanOneDevResult)
 			grp := dgroup.NewGroup(ctx, dgroup.GroupConfig{})
 			for _, dev := range fs.LV.PhysicalVolumes() {
+				dev := dev
 				grp.Go(dev.Name(), func(ctx context.Context) error {
 					superblock, err := dev.Superblock()
 					if err != nil {