Work on the new rebuildmappings

rebuildmappings.go didn't actually change very much, but was reworked to
be multi-device, so the diff looks like it totally changed.

1 files changed, 164 insertions, 0 deletions

diff --git a/lib/btrfsprogs/btrfsinspect/rebuildmappings/rebuildmappings.go b/lib/btrfsprogs/btrfsinspect/rebuildmappings/rebuildmappings.go
new file mode 100644
index 0000000..ce3b7ed
--- /dev/null
+++ b/lib/btrfsprogs/btrfsinspect/rebuildmappings/rebuildmappings.go
@@ -0,0 +1,164 @@
+// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package rebuildmappings
+
+import (
+	"context"
+	"fmt"
+	"sort"
+
+	"github.com/datawire/dlib/dlog"
+
+	"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/containers"
+	"git.lukeshu.com/btrfs-progs-ng/lib/maps"
+)
+
+func getNodeSize(fs *btrfs.FS) (btrfsvol.AddrDelta, error) {
+	sb, err := fs.Superblock()
+	if err != nil {
+		return 0, err
+	}
+	return btrfsvol.AddrDelta(sb.NodeSize), nil
+}
+
+type blockgroup struct {
+	LAddr btrfsvol.LogicalAddr
+	Size  btrfsvol.AddrDelta
+	Flags btrfsvol.BlockGroupFlags
+}
+
+func dedupBlockGroups(scanResults btrfsinspect.ScanDevicesResult) []blockgroup {
+	bgsSet := make(map[blockgroup]struct{})
+	for _, devResults := range scanResults {
+		for _, bg := range devResults.FoundBlockGroups {
+			bgsSet[blockgroup{
+				LAddr: btrfsvol.LogicalAddr(bg.Key.ObjectID),
+				Size:  btrfsvol.AddrDelta(bg.Key.Offset),
+				Flags: bg.BG.Flags,
+			}] = struct{}{}
+		}
+	}
+	bgsOrdered := maps.Keys(bgsSet)
+	sort.Slice(bgsOrdered, func(i, j int) bool {
+		return bgsOrdered[i].LAddr < bgsOrdered[j].LAddr
+	})
+	return bgsOrdered
+}
+
+func RebuildMappings(ctx context.Context, fs *btrfs.FS, scanResults btrfsinspect.ScanDevicesResult) error {
+	nodeSize, err := getNodeSize(fs)
+	if err != nil {
+		return err
+	}
+
+	var numChunks, numDevExts, numBlockGroups, numNodes int
+	devIDs := maps.SortedKeys(scanResults)
+	devices := fs.LV.PhysicalVolumes()
+	for _, devID := range devIDs {
+		if _, ok := devices[devID]; !ok {
+			return fmt.Errorf("device ID %v mentioned in scan results is not part of the filesystem", devID)
+		}
+		devResults := scanResults[devID]
+		numChunks += len(devResults.FoundChunks)
+		numDevExts += len(devResults.FoundDevExtents)
+		numBlockGroups += len(devResults.FoundBlockGroups)
+		for _, paddrs := range devResults.FoundNodes {
+			numNodes += len(paddrs)
+		}
+	}
+	dlog.Infof(ctx, "plan: 1/5 process %d chunks", numChunks)
+	dlog.Infof(ctx, "plan: 2/5 process %d device extents", numDevExts)
+	dlog.Infof(ctx, "plan: 3/5 process %d nodes", numNodes)
+	dlog.Infof(ctx, "plan: 4/5 process %d block groups", numBlockGroups)
+	dlog.Infof(ctx, "plan: 5/5 process sums")
+
+	dlog.Infof(ctx, "1/5: Processing %d chunks...", numChunks)
+	for _, devID := range devIDs {
+		devResults := scanResults[devID]
+		for _, chunk := range devResults.FoundChunks {
+			for _, mapping := range chunk.Chunk.Mappings(chunk.Key) {
+				if err := fs.LV.AddMapping(mapping); err != nil {
+					dlog.Errorf(ctx, "... error: adding chunk: %v", err)
+				}
+			}
+		}
+	}
+	dlog.Info(ctx, "... done processing chunks")
+
+	dlog.Infof(ctx, "2/5: Processing %d device extents...", numDevExts)
+	for _, devID := range devIDs {
+		devResults := scanResults[devID]
+		for _, ext := range devResults.FoundDevExtents {
+			if err := fs.LV.AddMapping(ext.DevExt.Mapping(ext.Key)); err != nil {
+				dlog.Errorf(ctx, "... error: adding devext: %v", err)
+			}
+		}
+	}
+	dlog.Info(ctx, "... done processing device extents")
+
+	// Do the nodes "last" to avoid bloating the mappings table
+	// too much.  (Because nodes are numerous and small, while the
+	// others are few and large; so it is likely that many of the
+	// nodes will be subsumed by other things.)
+	dlog.Infof(ctx, "3/5: Processing %d nodes...", numNodes)
+	for _, devID := range devIDs {
+		devResults := scanResults[devID]
+		// Sort them so that progress numbers are predictable.
+		for _, laddr := range maps.SortedKeys(devResults.FoundNodes) {
+			for _, paddr := range devResults.FoundNodes[laddr] {
+				if err := fs.LV.AddMapping(btrfsvol.Mapping{
+					LAddr: laddr,
+					PAddr: btrfsvol.QualifiedPhysicalAddr{
+						Dev:  devID,
+						Addr: paddr,
+					},
+					Size:       nodeSize,
+					SizeLocked: false,
+				}); err != nil {
+					dlog.Errorf(ctx, "... error: adding node ident: %v", err)
+				}
+			}
+		}
+	}
+	dlog.Info(ctx, "... done processing nodes")
+
+	// Use block groups to add missing flags (and as a hint to
+	// combine node entries).
+	dlog.Infof(ctx, "4/5: Processing %d block groups...", numBlockGroups)
+	// First dedup them, because they change for allocations and
+	// CoW means that they'll bounce around a lot, so you likely
+	// have oodles of duplicates?
+	bgsOrdered := dedupBlockGroups(scanResults)
+	for _, bg := range bgsOrdered {
+		otherLAddr, otherPAddr := fs.LV.ResolveAny(bg.LAddr, bg.Size)
+		if otherLAddr < 0 || otherPAddr.Addr < 0 {
+			dlog.Errorf(ctx, "... error: could not pair blockgroup laddr=%v (size=%v flags=%v) with a mapping",
+				bg.LAddr, bg.Size, bg.Flags)
+			continue
+		}
+
+		offsetWithinChunk := otherLAddr.Sub(bg.LAddr)
+		mapping := btrfsvol.Mapping{
+			LAddr:      bg.LAddr,
+			PAddr:      otherPAddr.Add(-offsetWithinChunk),
+			Size:       bg.Size,
+			SizeLocked: true,
+			Flags: containers.Optional[btrfsvol.BlockGroupFlags]{
+				OK:  true,
+				Val: bg.Flags,
+			},
+		}
+		if err := fs.LV.AddMapping(mapping); err != nil {
+			dlog.Errorf(ctx, "... error: adding flags from blockgroup: %v", err)
+		}
+	}
+	dlog.Info(ctx, "... done processing block groups")
+
+	dlog.Infof(ctx, "5/5: Processing sums: TODO")
+	return nil
+}