1 files changed, 125 insertions, 0 deletions
diff --git a/lib/btrfsprogs/btrfsinspect/scanforextents/csum.go b/lib/btrfsprogs/btrfsinspect/scanforextents/csum.go
new file mode 100644
index 0000000..7944497
--- /dev/null
+++ b/lib/btrfsprogs/btrfsinspect/scanforextents/csum.go
@@ -0,0 +1,125 @@
+// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package scanforextents
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/datawire/dlib/dlog"
+
+	"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/btrfssum"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
+)
+
+const csumBlockSize = 4 * 1024
+
+func ChecksumLogical(fs btrfs.Trees, alg btrfssum.CSumType, laddr btrfsvol.LogicalAddr) (btrfssum.CSum, error) {
+	var dat [csumBlockSize]byte
+	if _, err := fs.ReadAt(dat[:], laddr); err != nil {
+		return btrfssum.CSum{}, err
+	}
+	return alg.Sum(dat[:])
+}
+
+func ChecksumPhysical(dev *btrfs.Device, alg btrfssum.CSumType, paddr btrfsvol.PhysicalAddr) (btrfssum.CSum, error) {
+	var dat [csumBlockSize]byte
+	if _, err := dev.ReadAt(dat[:], paddr); err != nil {
+		return btrfssum.CSum{}, err
+	}
+	return alg.Sum(dat[:])
+}
+
+func ChecksumQualifiedPhysical(fs *btrfs.FS, alg btrfssum.CSumType, paddr btrfsvol.QualifiedPhysicalAddr) (btrfssum.CSum, error) {
+	dev := fs.LV.PhysicalVolumes()[paddr.Dev]
+	if dev == nil {
+		return btrfssum.CSum{}, fmt.Errorf("no such device_id=%v", paddr.Dev)
+	}
+	return ChecksumPhysical(dev, alg, paddr.Addr)
+}
+
+type shortSum string
+
+func readCSumTree(ctx context.Context, fs btrfs.Trees) map[shortSum][]btrfsvol.LogicalAddr {
+	sb, _ := fs.Superblock()
+
+	sum2laddrs := make(map[shortSum][]btrfsvol.LogicalAddr)
+	var cntUnmapped, cntErr, cntMismatch, cntValid int
+	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, treeSum := range body.Sums {
+					laddr := btrfsvol.LogicalAddr(item.Key.Offset) + (btrfsvol.LogicalAddr(i) * csumBlockSize)
+					readSum, err := ChecksumLogical(fs, sb.ChecksumType, laddr)
+					if err != nil {
+						if errors.Is(err, btrfsvol.ErrCouldNotMap) {
+							cntUnmapped++
+							treeShortSum := shortSum(treeSum[:body.ChecksumSize])
+							sum2laddrs[treeShortSum] = append(sum2laddrs[treeShortSum], laddr)
+							continue
+						}
+						dlog.Error(ctx, err)
+						cntErr++
+						continue
+					}
+					if readSum != treeSum {
+						dlog.Errorf(ctx, "checksum mismatch at laddr=%v: CSUM_TREE=%v != read=%v",
+							laddr, treeSum, readSum)
+						cntMismatch++
+						continue
+					}
+					cntValid++
+				}
+				return nil
+			},
+		},
+	)
+
+	total := cntErr + cntUnmapped + cntMismatch + cntValid
+	dlog.Infof(ctx, "  checksum errors          : %v", cntErr)
+	dlog.Infof(ctx, "  unmapped checksums       : %v", cntUnmapped)
+	dlog.Infof(ctx, "  mismatched checksums     : %v", cntMismatch)
+	dlog.Infof(ctx, "  valid checksums          : %v", cntValid)
+	dlog.Infof(ctx, "  -------------------------:")
+	dlog.Infof(ctx, "  total checksums          : %v", total)
+	dlog.Infof(ctx, "  distinct unmapped        : %v", len(sum2laddrs))
+
+	return sum2laddrs
+}
+
+func LookupCSum(fs btrfs.Trees, alg btrfssum.CSumType, laddr btrfsvol.LogicalAddr) (btrfssum.CSum, error) {
+	item, err := fs.TreeSearch(btrfs.CSUM_TREE_OBJECTID, func(key btrfs.Key, size uint32) int {
+		itemBeg := btrfsvol.LogicalAddr(key.ObjectID)
+		numSums := int64(size) / int64(alg.Size())
+		itemEnd := itemBeg + btrfsvol.LogicalAddr(numSums*csumBlockSize)
+		switch {
+		case itemEnd <= laddr:
+			return 1
+		case laddr < itemBeg:
+			return -1
+		default:
+			return 0
+		}
+	})
+	if err != nil {
+		return btrfssum.CSum{}, err
+	}
+	body, ok := item.Body.(btrfsitem.ExtentCSum)
+	if !ok {
+		return btrfssum.CSum{}, fmt.Errorf("item body is %T not ExtentCSum", item.Body)
+	}
+	return body.Sums[int(laddr-btrfsvol.LogicalAddr(item.Key.ObjectID))/csumBlockSize], nil
+}