bisync: generate final listing from sync results, not relisting -- fixes #5676

Before this change, if there were changes to sync, bisync listed each path
twice: once before the sync and once after. The second listing caused quite
a lot of problems, in addition to making each run much slower and more
expensive. A serious side-effect was that file changes could slip through
undetected, if they happened to occur while a sync was running (between the
first and second listing snapshots.)

After this change, the second listing is eliminated by getting the underlying
sync operation to report back a list of what it changed. Not only is this more
efficient, but also much more robust to concurrent modifications. It should no
longer be necessary to avoid make changes while it's running -- bisync will
simply learn about those changes next time and handle them on the next run.
Additionally, this also makes --check-sync usable again.

For further discussion, see:
https://forum.rclone.org/t/bisync-bugs-and-feature-requests/37636#:~:text=5.%20Final%20listings%20should%20be%20created%20from%20initial%20snapshot%20%2B%20deltas%2C%20not%20full%20re%2Dscans%2C%20to%20avoid%20errors%20if%20files%20changed%20during%20sync

cmd/bisync/bilib/canonical.go

@@ -11,7 +11,7 @@ import (
 )
 
 // FsPath converts Fs to a suitable rclone argument
-func FsPath(f fs.Fs) string {
+func FsPath(f fs.Info) string {
 	name, path, slash := f.Name(), f.Root(), "/"
 	if name == "local" {
 		slash = string(os.PathSeparator)

cmd/bisync/bisync_test.go

@@ -641,6 +641,8 @@ func (b *bisyncTest) runBisync(ctx context.Context, args []string) (err error) {
 		case "subdir":
 			fs1 = addSubdir(b.path1, val)
 			fs2 = addSubdir(b.path2, val)
+		case "ignore-listing-checksum":
+			opt.IgnoreListingChecksum = true
 		default:
 			return fmt.Errorf("invalid bisync option %q", arg)
 		}

cmd/bisync/deltas.go

@@ -176,9 +176,11 @@ func (b *bisyncRun) findDeltas(fctx context.Context, f fs.Fs, oldListing, newLis
 		} else {
 			if old.getTime(file) != now.getTime(file) {
 				if old.beforeOther(now, file) {
+					fs.Debugf(file, "(old: %v current: %v", old.getTime(file), now.getTime(file))
 					b.indent(msg, file, "File is newer")
 					d |= deltaNewer
 				} else { // Current version is older than prior sync.
+					fs.Debugf(file, "(old: %v current: %v", old.getTime(file), now.getTime(file))
 					b.indent(msg, file, "File is OLDER")
 					d |= deltaOlder
 				}
@@ -217,7 +219,7 @@ func (b *bisyncRun) findDeltas(fctx context.Context, f fs.Fs, oldListing, newLis
 }
 
 // applyDeltas
-func (b *bisyncRun) applyDeltas(ctx context.Context, ds1, ds2 *deltaSet) (changes1, changes2 bool, err error) {
+func (b *bisyncRun) applyDeltas(ctx context.Context, ds1, ds2 *deltaSet) (changes1, changes2 bool, results2to1, results1to2 []Results, queues queues, err error) {
 	path1 := bilib.FsPath(b.fs1)
 	path2 := bilib.FsPath(b.fs2)
 
@@ -226,6 +228,10 @@ func (b *bisyncRun) applyDeltas(ctx context.Context, ds1, ds2 *deltaSet) (change
 	delete1 := bilib.Names{}
 	delete2 := bilib.Names{}
 	handled := bilib.Names{}
+	renamed1 := bilib.Names{}
+	renamed2 := bilib.Names{}
+	renameSkipped := bilib.Names{}
+	deletedonboth := bilib.Names{}
 
 	ctxMove := b.opt.setDryRun(ctx)
 
@@ -299,6 +305,7 @@ func (b *bisyncRun) applyDeltas(ctx context.Context, ds1, ds2 *deltaSet) (change
 					equal := matches.Has(file)
 					if equal {
 						fs.Infof(nil, "Files are equal! Skipping: %s", file)
+						renameSkipped.Add(file)
 					} else {
 						fs.Debugf(nil, "Files are NOT equal: %s", file)
 						b.indent("!Path1", p1+"..path1", "Renaming Path1 copy")
@@ -307,6 +314,11 @@ func (b *bisyncRun) applyDeltas(ctx context.Context, ds1, ds2 *deltaSet) (change
 							b.critical = true
 							return
 						}
+						if b.opt.DryRun {
+							renameSkipped.Add(file)
+						} else {
+							renamed1.Add(file)
+						}
 						b.indent("!Path1", p2+"..path1", "Queue copy to Path2")
 						copy1to2.Add(file + "..path1")
 
@@ -315,6 +327,11 @@ func (b *bisyncRun) applyDeltas(ctx context.Context, ds1, ds2 *deltaSet) (change
 							err = fmt.Errorf("path2 rename failed for %s: %w", file, err)
 							return
 						}
+						if b.opt.DryRun {
+							renameSkipped.Add(file)
+						} else {
+							renamed2.Add(file)
+						}
 						b.indent("!Path2", p1+"..path2", "Queue copy to Path1")
 						copy2to1.Add(file + "..path2")
 					}
@@ -334,6 +351,7 @@ func (b *bisyncRun) applyDeltas(ctx context.Context, ds1, ds2 *deltaSet) (change
 				handled.Add(file)
 			} else if d2.is(deltaDeleted) {
 				handled.Add(file)
+				deletedonboth.Add(file)
 			}
 		}
 	}
@@ -360,25 +378,25 @@ func (b *bisyncRun) applyDeltas(ctx context.Context, ds1, ds2 *deltaSet) (change
 	if copy2to1.NotEmpty() {
 		changes1 = true
 		b.indent("Path2", "Path1", "Do queued copies to")
-		err = b.fastCopy(ctx, b.fs2, b.fs1, copy2to1, "copy2to1")
+		results2to1, err = b.fastCopy(ctx, b.fs2, b.fs1, copy2to1, "copy2to1")
 		if err != nil {
 			return
 		}
 
 		//copy empty dirs from path2 to path1 (if --create-empty-src-dirs)
-		b.syncEmptyDirs(ctx, b.fs1, copy2to1, dirs2, "make")
+		b.syncEmptyDirs(ctx, b.fs1, copy2to1, dirs2, &results2to1, "make")
 	}
 
 	if copy1to2.NotEmpty() {
 		changes2 = true
 		b.indent("Path1", "Path2", "Do queued copies to")
-		err = b.fastCopy(ctx, b.fs1, b.fs2, copy1to2, "copy1to2")
+		results1to2, err = b.fastCopy(ctx, b.fs1, b.fs2, copy1to2, "copy1to2")
 		if err != nil {
 			return
 		}
 
 		//copy empty dirs from path1 to path2 (if --create-empty-src-dirs)
-		b.syncEmptyDirs(ctx, b.fs2, copy1to2, dirs1, "make")
+		b.syncEmptyDirs(ctx, b.fs2, copy1to2, dirs1, &results1to2, "make")
 	}
 
 	if delete1.NotEmpty() {
@@ -386,7 +404,7 @@ func (b *bisyncRun) applyDeltas(ctx context.Context, ds1, ds2 *deltaSet) (change
 			return
 		}
 		//propagate deletions of empty dirs from path2 to path1 (if --create-empty-src-dirs)
-		b.syncEmptyDirs(ctx, b.fs1, delete1, dirs1, "remove")
+		b.syncEmptyDirs(ctx, b.fs1, delete1, dirs1, &results2to1, "remove")
 	}
 
 	if delete2.NotEmpty() {
@@ -394,9 +412,16 @@ func (b *bisyncRun) applyDeltas(ctx context.Context, ds1, ds2 *deltaSet) (change
 			return
 		}
 		//propagate deletions of empty dirs from path1 to path2 (if --create-empty-src-dirs)
-		b.syncEmptyDirs(ctx, b.fs2, delete2, dirs2, "remove")
+		b.syncEmptyDirs(ctx, b.fs2, delete2, dirs2, &results1to2, "remove")
 	}
 
+	queues.copy1to2 = copy1to2
+	queues.copy2to1 = copy2to1
+	queues.renamed1 = renamed1
+	queues.renamed2 = renamed2
+	queues.renameSkipped = renameSkipped
+	queues.deletedonboth = deletedonboth
+
 	return
 }
 

cmd/bisync/listing.go

@@ -9,14 +9,18 @@ import (
 	"io"
 	"os"
 	"regexp"
+	"sort"
 	"strconv"
 	"strings"
 	"sync"
 	"time"
 
 	"github.com/rclone/rclone/fs"
+	"github.com/rclone/rclone/fs/filter"
 	"github.com/rclone/rclone/fs/hash"
+	"github.com/rclone/rclone/fs/operations"
 	"github.com/rclone/rclone/fs/walk"
+	"golang.org/x/exp/slices"
 )
 
 // ListingHeader defines first line of a listing
@@ -70,11 +74,29 @@ func (ls *fileList) empty() bool {
 
 func (ls *fileList) has(file string) bool {
 	_, found := ls.info[file]
+	if !found {
+		//try unquoting
+		file, _ = strconv.Unquote(`"` + file + `"`)
+		_, found = ls.info[file]
+	}
 	return found
 }
 
 func (ls *fileList) get(file string) *fileInfo {
-	return ls.info[file]
+	info, found := ls.info[file]
+	if !found {
+		//try unquoting
+		file, _ = strconv.Unquote(`"` + file + `"`)
+		info = ls.info[fmt.Sprint(file)]
+	}
+	return info
+}
+
+func (ls *fileList) remove(file string) {
+	if ls.has(file) {
+		ls.list = slices.Delete(ls.list, slices.Index(ls.list, file), slices.Index(ls.list, file)+1)
+		delete(ls.info, file)
+	}
 }
 
 func (ls *fileList) put(file string, size int64, time time.Time, hash, id string, flags string) {
@@ -82,6 +104,9 @@ func (ls *fileList) put(file string, size int64, time time.Time, hash, id string
 	if fi != nil {
 		fi.size = size
 		fi.time = time
+		fi.hash = hash
+		fi.id = id
+		fi.flags = flags
 	} else {
 		fi = &fileInfo{
 			size:  size,
@@ -120,12 +145,20 @@ func (ls *fileList) afterTime(file string, time time.Time) bool {
 	return fi.time.After(time)
 }
 
+// sort by path name
+func (ls *fileList) sort() {
+	sort.SliceStable(ls.list, func(i, j int) bool {
+		return ls.list[i] < ls.list[j]
+	})
+}
+
 // save will save listing to a file.
 func (ls *fileList) save(ctx context.Context, listing string) error {
 	file, err := os.Create(listing)
 	if err != nil {
 		return err
 	}
+	ls.sort()
 
 	hashName := ""
 	if ls.hash != hash.None {
@@ -376,3 +409,221 @@ func (b *bisyncRun) listDirsOnly(listingNum int) (*fileList, error) {
 
 	return dirsonly, err
 }
+
+// ConvertPrecision returns the Modtime rounded to Dest's precision if lower, otherwise unchanged
+// Need to use the other fs's precision (if lower) when copying
+// Note: we need to use Truncate rather than Round so that After() is reliable.
+// (2023-11-02 20:22:45.552679442 +0000 < UTC 2023-11-02 20:22:45.553 +0000 UTC)
+func ConvertPrecision(Modtime time.Time, dst fs.Fs) time.Time {
+	DestPrecision := dst.Precision()
+
+	// In case it's wrapping an Fs with lower precision, try unwrapping and use the lowest.
+	if Modtime.Truncate(DestPrecision).After(Modtime.Truncate(fs.UnWrapFs(dst).Precision())) {
+		DestPrecision = fs.UnWrapFs(dst).Precision()
+	}
+
+	if Modtime.After(Modtime.Truncate(DestPrecision)) {
+		return Modtime.Truncate(DestPrecision)
+	}
+	return Modtime
+}
+
+// modifyListing will modify the listing based on the results of the sync
+func (b *bisyncRun) modifyListing(ctx context.Context, src fs.Fs, dst fs.Fs, srcListing string, dstListing string, results []Results, queues queues, is1to2 bool) (err error) {
+	queue := queues.copy2to1
+	renames := queues.renamed2
+	direction := "2to1"
+	if is1to2 {
+		queue = queues.copy1to2
+		renames = queues.renamed1
+		direction = "1to2"
+	}
+
+	fs.Debugf(nil, "updating %s", direction)
+	fs.Debugf(nil, "RESULTS: %v", results)
+	fs.Debugf(nil, "QUEUE: %v", queue)
+
+	srcList, err := b.loadListing(srcListing)
+	if err != nil {
+		return fmt.Errorf("cannot read prior listing: %w", err)
+	}
+	dstList, err := b.loadListing(dstListing)
+	if err != nil {
+		return fmt.Errorf("cannot read prior listing: %w", err)
+	}
+	// set list hash type
+	if b.opt.Resync && !b.opt.IgnoreListingChecksum {
+		srcList.hash = src.Hashes().GetOne()
+		dstList.hash = dst.Hashes().GetOne()
+	}
+
+	srcWinners := newFileList()
+	dstWinners := newFileList()
+	errors := newFileList()
+	ctxRecheck, filterRecheck := filter.AddConfig(ctx)
+
+	for _, result := range results {
+		if result.Name == "" {
+			continue
+		}
+
+		if result.Flags == "d" && !b.opt.CreateEmptySrcDirs {
+			continue
+		}
+
+		// build src winners list
+		if result.IsSrc && result.Src != "" && (result.Winner.Err == nil || result.Flags == "d") {
+			srcWinners.put(result.Name, result.Size, ConvertPrecision(result.Modtime, src), result.Hash, "-", result.Flags)
+			fs.Debugf(nil, "winner: copy to src: %v", result)
+		}
+
+		// build dst winners list
+		if result.IsWinner && result.Winner.Side != "none" && (result.Winner.Err == nil || result.Flags == "d") {
+			dstWinners.put(result.Name, result.Size, ConvertPrecision(result.Modtime, dst), result.Hash, "-", result.Flags)
+			fs.Debugf(nil, "winner: copy to dst: %v", result)
+		}
+
+		// build errors list
+		if result.Err != nil || result.Winner.Err != nil {
+			errors.put(result.Name, result.Size, result.Modtime, result.Hash, "-", result.Flags)
+			if err := filterRecheck.AddFile(result.Name); err != nil {
+				fs.Debugf(result.Name, "error adding file to recheck filter: %v", err)
+			}
+		}
+	}
+
+	updateLists := func(side string, winners, list *fileList) {
+		// removals from side
+		for _, oldFile := range queue.ToList() {
+			if !winners.has(oldFile) && list.has(oldFile) && !errors.has(oldFile) {
+				list.remove(oldFile)
+				fs.Debugf(nil, "decision: removed from %s: %v", side, oldFile)
+			} else if winners.has(oldFile) {
+				// copies to side
+				new := winners.get(oldFile)
+				list.put(oldFile, new.size, new.time, new.hash, new.id, new.flags)
+				fs.Debugf(nil, "decision: copied to %s: %v", side, oldFile)
+			} else {
+				fs.Debugf(oldFile, "file in queue but missing from %s transfers", side)
+				if err := filterRecheck.AddFile(oldFile); err != nil {
+					fs.Debugf(oldFile, "error adding file to recheck filter: %v", err)
+				}
+			}
+		}
+	}
+	updateLists("src", srcWinners, srcList)
+	updateLists("dst", dstWinners, dstList)
+
+	// TODO: rollback on error
+
+	// account for "deltaOthers" we handled separately
+	if queues.deletedonboth.NotEmpty() {
+		for file := range queues.deletedonboth {
+			srcList.remove(file)
+			dstList.remove(file)
+		}
+	}
+	if renames.NotEmpty() && !b.opt.DryRun {
+		// renamed on src and copied to dst
+		renamesList := renames.ToList()
+		for _, file := range renamesList {
+			// we'll handle the other side when we go the other direction
+			newName := file + "..path2"
+			oppositeName := file + "..path1"
+			if is1to2 {
+				newName = file + "..path1"
+				oppositeName = file + "..path2"
+			}
+			var new *fileInfo
+			// we prefer to get the info from the ..path1 / ..path2 versions
+			// since they were actually copied as opposed to operations.MoveFile()'d.
+			// the size/time/hash info is therefore fresher on the renames
+			// but we'll settle for the original if we have to.
+			if srcList.has(newName) {
+				new = srcList.get(newName)
+			} else if srcList.has(oppositeName) {
+				new = srcList.get(oppositeName)
+			} else if srcList.has(file) {
+				new = srcList.get(file)
+			} else {
+				if err := filterRecheck.AddFile(file); err != nil {
+					fs.Debugf(file, "error adding file to recheck filter: %v", err)
+				}
+			}
+			srcList.put(newName, new.size, new.time, new.hash, new.id, new.flags)
+			dstList.put(newName, new.size, ConvertPrecision(new.time, src), new.hash, new.id, new.flags)
+			srcList.remove(file)
+			dstList.remove(file)
+		}
+	}
+
+	// recheck the ones we skipped because they were equal
+	// we never got their info because they were never synced.
+	// TODO: add flag to skip this for people who don't care and would rather avoid?
+	if queues.renameSkipped.NotEmpty() {
+		skippedList := queues.renameSkipped.ToList()
+		for _, file := range skippedList {
+			if err := filterRecheck.AddFile(file); err != nil {
+				fs.Debugf(file, "error adding file to recheck filter: %v", err)
+			}
+		}
+	}
+
+	if filterRecheck.HaveFilesFrom() {
+		b.recheck(ctxRecheck, src, dst, srcList, dstList)
+	}
+
+	// update files
+	err = srcList.save(ctx, srcListing)
+	if err != nil {
+		b.abort = true
+	}
+	err = dstList.save(ctx, dstListing)
+	if err != nil {
+		b.abort = true
+	}
+
+	return err
+}
+
+// recheck the ones we're not sure about
+func (b *bisyncRun) recheck(ctxRecheck context.Context, src, dst fs.Fs, srcList, dstList *fileList) {
+	var srcObjs []fs.Object
+	var dstObjs []fs.Object
+
+	if err := operations.ListFn(ctxRecheck, src, func(obj fs.Object) {
+		srcObjs = append(srcObjs, obj)
+	}); err != nil {
+		fs.Debugf(src, "error recchecking src obj: %v", err)
+	}
+	if err := operations.ListFn(ctxRecheck, dst, func(obj fs.Object) {
+		dstObjs = append(dstObjs, obj)
+	}); err != nil {
+		fs.Debugf(dst, "error recchecking dst obj: %v", err)
+	}
+
+	putObj := func(obj fs.Object, f fs.Fs, list *fileList) {
+		hashVal := ""
+		if !b.opt.IgnoreListingChecksum {
+			hashType := f.Hashes().GetOne()
+			if hashType != hash.None {
+				hashVal, _ = obj.Hash(ctxRecheck, hashType)
+			}
+		}
+		list.put(obj.Remote(), obj.Size(), obj.ModTime(ctxRecheck), hashVal, "-", "-")
+	}
+
+	for _, srcObj := range srcObjs {
+		fs.Debugf(srcObj, "rechecking")
+		for _, dstObj := range dstObjs {
+			if srcObj.Remote() == dstObj.Remote() {
+				if operations.Equal(ctxRecheck, srcObj, dstObj) || b.opt.DryRun {
+					putObj(srcObj, src, srcList)
+					putObj(dstObj, dst, dstList)
+				} else {
+					fs.Infof(srcObj, "files not equal on recheck: %v %v", srcObj, dstObj)
+				}
+			}
+		}
+	}
+}

cmd/bisync/operations.go

@@ -16,7 +16,6 @@ import (
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/filter"
 	"github.com/rclone/rclone/fs/operations"
-	"github.com/rclone/rclone/fs/sync"
 	"github.com/rclone/rclone/lib/atexit"
 )
 
@@ -35,6 +34,15 @@ type bisyncRun struct {
 	opt       *Options
 }
 
+type queues struct {
+	copy1to2      bilib.Names
+	copy2to1      bilib.Names
+	renamed1      bilib.Names // renamed on 1 and copied to 2
+	renamed2      bilib.Names // renamed on 2 and copied to 1
+	renameSkipped bilib.Names // not renamed because it was equal
+	deletedonboth bilib.Names
+}
+
 // Bisync handles lock file, performs bisync run and checks exit status
 func Bisync(ctx context.Context, fs1, fs2 fs.Fs, optArg *Options) (err error) {
 	opt := *optArg // ensure that input is never changed
@@ -256,13 +264,18 @@ func (b *bisyncRun) runLocked(octx context.Context, listing1, listing2 string) (
 
 	// Determine and apply changes to Path1 and Path2
 	noChanges := ds1.empty() && ds2.empty()
-	changes1 := false
+	changes1 := false // 2to1
-	changes2 := false
+	changes2 := false // 1to2
+	results2to1 := []Results{}
+	results1to2 := []Results{}
+
+	queues := queues{}
+
 	if noChanges {
 		fs.Infof(nil, "No changes found")
 	} else {
 		fs.Infof(nil, "Applying changes")
-		changes1, changes2, err = b.applyDeltas(octx, ds1, ds2)
+		changes1, changes2, results2to1, results1to2, queues, err = b.applyDeltas(octx, ds1, ds2)
 		if err != nil {
 			b.critical = true
 			// b.retryable = true // not sure about this one
@@ -277,13 +290,13 @@ func (b *bisyncRun) runLocked(octx context.Context, listing1, listing2 string) (
 		err1 = bilib.CopyFileIfExists(newListing1, listing1)
 		err2 = bilib.CopyFileIfExists(newListing2, listing2)
 	} else {
-		if changes1 {
+		if changes1 { // 2to1
-			_, err1 = b.makeListing(fctx, b.fs1, listing1)
+			err1 = b.modifyListing(fctx, b.fs2, b.fs1, listing2, listing1, results2to1, queues, false)
 		} else {
 			err1 = bilib.CopyFileIfExists(newListing1, listing1)
 		}
-		if changes2 {
+		if changes2 { // 1to2
-			_, err2 = b.makeListing(fctx, b.fs2, listing2)
+			err2 = b.modifyListing(fctx, b.fs1, b.fs2, listing1, listing2, results1to2, queues, true)
 		} else {
 			err2 = bilib.CopyFileIfExists(newListing2, listing2)
 		}
@@ -394,11 +407,15 @@ func (b *bisyncRun) resync(octx, fctx context.Context, listing1, listing2 string
 			copy2to1 = append(copy2to1, file)
 		}
 	}
+	var results2to1 []Results
+	var results1to2 []Results
+	var results2to1Dirs []Results
+	queues := queues{}
 
 	if len(copy2to1) > 0 {
 		b.indent("Path2", "Path1", "Resync is doing queued copies to")
 		// octx does not have extra filters!
-		err = b.fastCopy(octx, b.fs2, b.fs1, bilib.ToNames(copy2to1), "resync-copy2to1")
+		results2to1, err = b.fastCopy(octx, b.fs2, b.fs1, bilib.ToNames(copy2to1), "resync-copy2to1")
 		if err != nil {
 			b.critical = true
 			return err
@@ -413,7 +430,7 @@ func (b *bisyncRun) resync(octx, fctx context.Context, listing1, listing2 string
 		// prevent overwriting Google Doc files (their size is -1)
 		filterSync.Opt.MinSize = 0
 	}
-	if err = sync.CopyDir(ctxSync, b.fs2, b.fs1, b.opt.CreateEmptySrcDirs); err != nil {
+	if results1to2, err = b.resyncDir(ctxSync, b.fs1, b.fs2); err != nil {
 		b.critical = true
 		return err
 	}
@@ -435,19 +452,38 @@ func (b *bisyncRun) resync(octx, fctx context.Context, listing1, listing2 string
 		fs.Infof(nil, "Resynching Path2 to Path1 (for empty dirs)")
 
 		// note copy (not sync) and dst comes before src
-		if err = sync.CopyDir(ctxSync, b.fs1, b.fs2, b.opt.CreateEmptySrcDirs); err != nil {
+		if results2to1Dirs, err = b.resyncDir(ctxSync, b.fs2, b.fs1); err != nil {
 			b.critical = true
 			return err
 		}
 	}
 
 	fs.Infof(nil, "Resync updating listings")
-	if _, err = b.makeListing(fctx, b.fs1, listing1); err != nil {
+	if err := bilib.CopyFileIfExists(newListing1, listing1); err != nil {
+		return err
+	}
+	if err := bilib.CopyFileIfExists(newListing2, listing2); err != nil {
+		return err
+	}
+
+	// resync 2to1
+	queues.copy2to1 = bilib.ToNames(copy2to1)
+	if err = b.modifyListing(fctx, b.fs2, b.fs1, listing2, listing1, results2to1, queues, false); err != nil {
 		b.critical = true
 		return err
 	}
 
-	if _, err = b.makeListing(fctx, b.fs2, listing2); err != nil {
+	// resync 1to2
+	queues.copy1to2 = bilib.ToNames(filesNow1.list)
+	if err = b.modifyListing(fctx, b.fs1, b.fs2, listing1, listing2, results1to2, queues, true); err != nil {
+		b.critical = true
+		return err
+	}
+
+	// resync 2to1 (dirs)
+	dirs2, _ := b.listDirsOnly(2)
+	queues.copy2to1 = bilib.ToNames(dirs2.list)
+	if err = b.modifyListing(fctx, b.fs2, b.fs1, listing2, listing1, results2to1Dirs, queues, false); err != nil {
 		b.critical = true
 		return err
 	}

cmd/bisync/queue.go

@@ -2,39 +2,187 @@ package bisync
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
+	"io"
 	"sort"
+	mutex "sync" // renamed as "sync" already in use
+	"time"
 
 	"github.com/rclone/rclone/cmd/bisync/bilib"
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/filter"
 	"github.com/rclone/rclone/fs/operations"
 	"github.com/rclone/rclone/fs/sync"
+	"golang.org/x/text/unicode/norm"
 )
 
-func (b *bisyncRun) fastCopy(ctx context.Context, fsrc, fdst fs.Fs, files bilib.Names, queueName string) error {
+// Results represents a pair of synced files, as reported by the LoggerFn
+// Bisync uses this to determine what happened during the sync, and modify the listings accordingly
+type Results struct {
+	Src      string
+	Dst      string
+	Name     string
+	Size     int64
+	Modtime  time.Time
+	Hash     string
+	Flags    string
+	Sigil    operations.Sigil
+	Err      error
+	Winner   operations.Winner
+	IsWinner bool
+	IsSrc    bool
+	IsDst    bool
+}
+
+var logger = operations.NewLoggerOpt()
+var lock mutex.Mutex
+var ignoreListingChecksum bool
+
+// FsPathIfAny handles type assertions and returns a formatted bilib.FsPath if valid, otherwise ""
+func FsPathIfAny(x fs.DirEntry) string {
+	obj, ok := x.(fs.Object)
+	if x != nil && ok {
+		return bilib.FsPath(obj.Fs())
+	}
+	return ""
+}
+
+func resultName(result Results, side, src, dst fs.DirEntry) string {
+	if side != nil {
+		return side.Remote()
+	} else if result.IsSrc && dst != nil {
+		return dst.Remote()
+	} else if src != nil {
+		return src.Remote()
+	}
+	return ""
+}
+
+// WriteResults is Bisync's LoggerFn
+func WriteResults(ctx context.Context, sigil operations.Sigil, src, dst fs.DirEntry, err error) {
+	lock.Lock()
+	defer lock.Unlock()
+
+	opt := operations.GetLoggerOpt(ctx)
+	result := Results{
+		Sigil: sigil,
+		Src:   FsPathIfAny(src),
+		Dst:   FsPathIfAny(dst),
+		Err:   err,
+	}
+
+	result.Winner = operations.WinningSide(ctx, sigil, src, dst, err)
+
+	fss := []fs.DirEntry{src, dst}
+	for i, side := range fss {
+
+		result.Name = resultName(result, side, src, dst)
+		result.IsSrc = i == 0
+		result.IsDst = i == 1
+		result.Flags = "-"
+		if side != nil {
+			result.Size = side.Size()
+			result.Modtime = side.ModTime(ctx).In(time.UTC)
+
+			if !ignoreListingChecksum {
+				sideObj, ok := side.(fs.ObjectInfo)
+				if ok {
+					result.Hash, _ = sideObj.Hash(ctx, sideObj.Fs().Hashes().GetOne())
+				}
+			}
+		}
+		result.IsWinner = result.Winner.Obj == side
+
+		// used during resync only
+		if err == fs.ErrorIsDir {
+			if src != nil {
+				result.Src = src.Remote()
+				result.Name = src.Remote()
+			} else {
+				result.Dst = dst.Remote()
+				result.Name = dst.Remote()
+			}
+			result.Flags = "d"
+			result.Size = 0
+		}
+
+		fs.Debugf(nil, "writing result: %v", result)
+		err := json.NewEncoder(opt.JSON).Encode(result)
+		if err != nil {
+			fs.Errorf(result, "Error encoding JSON: %v", err)
+		}
+	}
+}
+
+// ReadResults decodes the JSON data from WriteResults
+func ReadResults(results io.Reader) []Results {
+	dec := json.NewDecoder(results)
+	var slice []Results
+	for {
+		var r Results
+		if err := dec.Decode(&r); err == io.EOF {
+			break
+		}
+		fs.Debugf(nil, "result: %v", r)
+		slice = append(slice, r)
+	}
+	return slice
+}
+
+func (b *bisyncRun) fastCopy(ctx context.Context, fsrc, fdst fs.Fs, files bilib.Names, queueName string) ([]Results, error) {
 	if err := b.saveQueue(files, queueName); err != nil {
-		return err
+		return nil, err
 	}
 
 	ctxCopy, filterCopy := filter.AddConfig(b.opt.setDryRun(ctx))
 	for _, file := range files.ToList() {
 		if err := filterCopy.AddFile(file); err != nil {
-			return err
+			return nil, err
+		}
+		// macOS
+		if err := filterCopy.AddFile(norm.NFD.String(file)); err != nil {
+			return nil, err
 		}
 	}
 
+	ignoreListingChecksum = b.opt.IgnoreListingChecksum
+	logger.LoggerFn = WriteResults
+	ctxCopyLogger := operations.WithSyncLogger(ctxCopy, logger)
 	var err error
 	if b.opt.Resync {
-		err = sync.CopyDir(ctxCopy, fdst, fsrc, b.opt.CreateEmptySrcDirs)
+		err = sync.CopyDir(ctxCopyLogger, fdst, fsrc, b.opt.CreateEmptySrcDirs)
 	} else {
-		err = sync.Sync(ctxCopy, fdst, fsrc, b.opt.CreateEmptySrcDirs)
+		err = sync.Sync(ctxCopyLogger, fdst, fsrc, b.opt.CreateEmptySrcDirs)
 	}
-	return err
+	fs.Debugf(nil, "logger is: %v", logger)
+
+	getResults := ReadResults(logger.JSON)
+	fs.Debugf(nil, "Got %v results for %v", len(getResults), queueName)
+
+	lineFormat := "%s %8d %s %s %s %q\n"
+	for _, result := range getResults {
+		fs.Debugf(nil, lineFormat, result.Flags, result.Size, result.Hash, "", result.Modtime, result.Name)
+	}
+
+	return getResults, err
+}
+
+func (b *bisyncRun) resyncDir(ctx context.Context, fsrc, fdst fs.Fs) ([]Results, error) {
+	ignoreListingChecksum = b.opt.IgnoreListingChecksum
+	logger.LoggerFn = WriteResults
+	ctxCopyLogger := operations.WithSyncLogger(ctx, logger)
+	err := sync.CopyDir(ctxCopyLogger, fdst, fsrc, b.opt.CreateEmptySrcDirs)
+	fs.Debugf(nil, "logger is: %v", logger)
+
+	getResults := ReadResults(logger.JSON)
+	fs.Debugf(nil, "Got %v results for %v", len(getResults), "resync")
+
+	return getResults, err
 }
 
 // operation should be "make" or "remove"
-func (b *bisyncRun) syncEmptyDirs(ctx context.Context, dst fs.Fs, candidates bilib.Names, dirsList *fileList, operation string) {
+func (b *bisyncRun) syncEmptyDirs(ctx context.Context, dst fs.Fs, candidates bilib.Names, dirsList *fileList, results *[]Results, operation string) {
 	if b.opt.CreateEmptySrcDirs && (!b.opt.Resync || operation == "make") {
 
 		candidatesList := candidates.ToList()
@@ -46,18 +194,50 @@ func (b *bisyncRun) syncEmptyDirs(ctx context.Context, dst fs.Fs, candidates bil
 		for _, s := range candidatesList {
 			var direrr error
 			if dirsList.has(s) { //make sure it's a dir, not a file
+				r := Results{}
+				r.Name = s
+				r.Size = 0
+				r.Modtime = dirsList.getTime(s).In(time.UTC)
+				r.Flags = "d"
+				r.Err = nil
+				r.Winner = operations.Winner{ // note: Obj not set
+					Side: "src",
+					Err:  nil,
+				}
+
+				rSrc := r
+				rDst := r
+				rSrc.IsSrc = true
+				rSrc.IsDst = false
+				rDst.IsSrc = false
+				rDst.IsDst = true
+				rSrc.IsWinner = true
+				rDst.IsWinner = false
+
 				if operation == "remove" {
 					// directories made empty by the sync will have already been deleted during the sync
 					// this just catches the already-empty ones (excluded from sync by --files-from filter)
 					direrr = operations.TryRmdir(ctx, dst, s)
+					rSrc.Sigil = operations.MissingOnSrc
+					rDst.Sigil = operations.MissingOnSrc
+					rSrc.Dst = s
+					rDst.Dst = s
+					rSrc.Winner.Side = "none"
+					rDst.Winner.Side = "none"
 				} else if operation == "make" {
 					direrr = operations.Mkdir(ctx, dst, s)
+					rSrc.Sigil = operations.MissingOnDst
+					rDst.Sigil = operations.MissingOnDst
+					rSrc.Src = s
+					rDst.Src = s
 				} else {
 					direrr = fmt.Errorf("invalid operation. Expected 'make' or 'remove', received '%q'", operation)
 				}
 
 				if direrr != nil {
 					fs.Debugf(nil, "Error syncing directory: %v", direrr)
+				} else {
+					*results = append(*results, rSrc, rDst)
 				}
 			}
 		}

cmd/bisync/testdata/test_ignorelistingchecksum/golden/_testdir_path1.._testdir_path2.copy1to2.que

@@ -0,0 +1 @@
+"subdir/file20.txt"

cmd/bisync/testdata/test_ignorelistingchecksum/golden/_testdir_path1.._testdir_path2.copy2to1.que

@@ -0,0 +1 @@
+"file1.txt"

cmd/bisync/testdata/test_ignorelistingchecksum/golden/_testdir_path1.._testdir_path2.path1.lst

@@ -0,0 +1,9 @@
+# bisync listing v1 from test
+-      109 - - 2000-01-01T00:00:00.000000000+0000 "RCLONE_TEST"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy1.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy2.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy3.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy4.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy5.txt"
+-       19 - - 2001-01-02T00:00:00.000000000+0000 "file1.txt"
+-       19 - - 2001-01-02T00:00:00.000000000+0000 "subdir/file20.txt"

cmd/bisync/testdata/test_ignorelistingchecksum/golden/_testdir_path1.._testdir_path2.path1.lst-new

@@ -0,0 +1,9 @@
+# bisync listing v1 from test
+-      109 - - 2000-01-01T00:00:00.000000000+0000 "RCLONE_TEST"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy1.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy2.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy3.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy4.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy5.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.txt"
+-       19 - - 2001-01-02T00:00:00.000000000+0000 "subdir/file20.txt"

cmd/bisync/testdata/test_ignorelistingchecksum/golden/_testdir_path1.._testdir_path2.path2.lst

@@ -0,0 +1,9 @@
+# bisync listing v1 from test
+-      109 - - 2000-01-01T00:00:00.000000000+0000 "RCLONE_TEST"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy1.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy2.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy3.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy4.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy5.txt"
+-       19 - - 2001-01-02T00:00:00.000000000+0000 "file1.txt"
+-       19 - - 2001-01-02T00:00:00.000000000+0000 "subdir/file20.txt"

cmd/bisync/testdata/test_ignorelistingchecksum/golden/_testdir_path1.._testdir_path2.path2.lst-new

@@ -0,0 +1,9 @@
+# bisync listing v1 from test
+-      109 - - 2000-01-01T00:00:00.000000000+0000 "RCLONE_TEST"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy1.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy2.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy3.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy4.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "file1.copy5.txt"
+-       19 - - 2001-01-02T00:00:00.000000000+0000 "file1.txt"
+-        0 - - 2000-01-01T00:00:00.000000000+0000 "subdir/file20.txt"

cmd/bisync/testdata/test_ignorelistingchecksum/golden/test.log

@@ -0,0 +1,39 @@
+(01)  : test basic
+
+
+(02)  : test initial bisync
+(03)  : bisync resync
+INFO  : Synching Path1 "{path1/}" with Path2 "{path2/}"
+INFO  : Copying unique Path2 files to Path1
+INFO  : Resynching Path1 to Path2
+INFO  : Resync updating listings
+INFO  : Bisync successful
+(04)  : bisync resync ignore-listing-checksum
+INFO  : Synching Path1 "{path1/}" with Path2 "{path2/}"
+INFO  : Copying unique Path2 files to Path1
+INFO  : Resynching Path1 to Path2
+INFO  : Resync updating listings
+INFO  : Bisync successful
+
+(05)  : test place newer files on both paths
+
+(06)  : touch-copy 2001-01-02 {datadir/}file1.txt {path2/}
+(07)  : copy-as {datadir/}file1.txt {path1/}subdir file20.txt
+
+(08)  : test bisync run
+(09)  : bisync ignore-listing-checksum
+INFO  : Synching Path1 "{path1/}" with Path2 "{path2/}"
+INFO  : Path1 checking for diffs
+INFO  : - Path1    File is newer                       - subdir/file20.txt
+INFO  : Path1:    1 changes:    0 new,    1 newer,    0 older,    0 deleted
+INFO  : Path2 checking for diffs
+INFO  : - Path2    File is newer                       - file1.txt
+INFO  : Path2:    1 changes:    0 new,    1 newer,    0 older,    0 deleted
+INFO  : Applying changes
+INFO  : - Path1    Queue copy to Path2                 - {path2/}subdir/file20.txt
+INFO  : - Path2    Queue copy to Path1                 - {path1/}file1.txt
+INFO  : - Path2    Do queued copies to                 - Path1
+INFO  : - Path1    Do queued copies to                 - Path2
+INFO  : Updating listings
+INFO  : Validating listings for Path1 "{path1/}" vs Path2 "{path2/}"
+INFO  : Bisync successful

cmd/bisync/testdata/test_ignorelistingchecksum/initial/RCLONE_TEST

@@ -0,0 +1 @@
+This file is used for testing the health of rclone accesses to the local/remote file system.  Do not delete.

cmd/bisync/testdata/test_ignorelistingchecksum/modfiles/file1.txt

@@ -0,0 +1 @@
+This file is newer

cmd/bisync/testdata/test_ignorelistingchecksum/scenario.txt

@@ -0,0 +1,14 @@
+test basic
+# Simple test case for development
+
+test initial bisync
+bisync resync
+bisync resync ignore-listing-checksum
+
+test place newer files on both paths
+# force specific modification time since file time is lost through git
+touch-copy 2001-01-02 {datadir/}file1.txt {path2/}
+copy-as {datadir/}file1.txt {path1/}subdir file20.txt
+
+test bisync run
+bisync ignore-listing-checksum

docs/content/bisync.md

@@ -277,7 +277,39 @@ sync run times for very large numbers of files.
 The check may be run manually with `--check-sync=only`. It runs only the
 integrity check and terminates without actually synching.
 
-See also: [Concurrent modifications](#concurrent-modifications)
+Note that currently, `--check-sync` **only checks filenames and NOT modtime, size, or hash.**
+For a more robust integrity check of the current state, consider using [`check`](commands/rclone_check/)
+(or [`cryptcheck`](/commands/rclone_cryptcheck/), if at least one path is a `crypt` remote.)
+For example, a possible sequence could look like this:
+
+1. Normally scheduled bisync run:
+
+```
+rclone bisync Path1 Path2 -MPc --check-access --max-delete 10 --filters-file /path/to/filters.txt -v --no-cleanup --ignore-listing-checksum --disable ListR --checkers=16 --drive-pacer-min-sleep=10ms --create-empty-src-dirs --resilient
+```
+
+2. Periodic independent integrity check (perhaps scheduled nightly or weekly):
+
+```
+rclone check -MvPc Path1 Path2 --filter-from /path/to/filters.txt
+```
+
+3. If diffs are found, you have some choices to correct them.
+If one side is more up-to-date and you want to make the other side match it, you could run:
+
+```
+rclone sync Path1 Path2 --filter-from /path/to/filters.txt --create-empty-src-dirs -MPc -v
+```
+(or switch Path1 and Path2 to make Path2 the source-of-truth)
+
+Or, if neither side is totally up-to-date, you could run a `--resync` to bring them back into agreement
+(but remember that this could cause deleted files to re-appear.)
+
+*Note also that `rclone check` does not currently include empty directories,
+so if you want to know if any empty directories are out of sync,
+consider alternatively running the above `rclone sync` command with `--dry-run` added.
+
+See also: [Concurrent modifications](#concurrent-modifications), [`--resilient`](#resilient)
 
 
 #### --ignore-listing-checksum
@@ -299,13 +331,6 @@ if there ARE diffs.
 * Unless `--ignore-listing-checksum` is passed, bisync currently computes hashes for one path 
 *even when there's no common hash with the other path* 
 (for example, a [crypt](/crypt/#modification-times-and-hashes) remote.)
-* If both paths support checksums and have a common hash, 
-AND `--ignore-listing-checksum` was not specified when creating the listings, 
-`--check-sync=only` can be used to compare Path1 vs. Path2 checksums (as of the time the previous listings were created.) 
-However, `--check-sync=only` will NOT include checksums if the previous listings 
-were generated on a run using `--ignore-listing-checksum`. For a more robust integrity check of the current state, 
-consider using [`check`](commands/rclone_check/) 
-(or [`cryptcheck`](/commands/rclone_cryptcheck/), if at least one path is a `crypt` remote.)
 
 #### --resilient
 
@@ -495,44 +520,18 @@ original path on the next sync, resulting in data loss.
 It is therefore recommended to _omit_ `--inplace`.
 
 Files that **change during** a bisync run may result in data loss.
-This has been seen in a highly dynamic environment, where the filesystem
+Prior to `rclone v1.65`, this was commonly seen in highly dynamic environments, where the filesystem
-is getting hammered by running processes during the sync.
+was getting hammered by running processes during the sync.
-The currently recommended solution is to sync at quiet times or [filter out](#filtering)
+As of `rclone v1.65`, bisync was redesigned to use a "snapshot" model,
-unnecessary directories and files.
+greatly reducing the risks from changes during a sync.
-
+Changes that are not detected during the current sync will now be detected during the following sync,
-As an [alternative approach](https://forum.rclone.org/t/bisync-bugs-and-feature-requests/37636#:~:text=scans%2C%20to%20avoid-,errors%20if%20files%20changed%20during%20sync,-Given%20the%20number), 
+and will no longer cause the entire run to throw a critical error.
-consider using `--check-sync=false` (and possibly `--resilient`) to make bisync more forgiving
+There is additionally a mechanism to mark files as needing to be internally rechecked next time, for added safety.
-of filesystems that change during the sync. 
+It should therefore no longer be necessary to sync only at quiet times --
-Be advised that this may cause bisync to miss events that occur during a bisync run, 
+however, note that an error can still occur if a file happens to change at the exact moment it's
-so it is a good idea to supplement this with a periodic independent integrity check, 
+being read/written by bisync (same as would happen in `rclone sync`.)
-and corrective sync if diffs are found. For example, a possible sequence could look like this:
+(See also: [`--ignore-checksum`](https://rclone.org/docs/#ignore-checksum),
-
+[`--local-no-check-updated`](https://rclone.org/local/#local-no-check-updated))
-1. Normally scheduled bisync run:
-
-```
-rclone bisync Path1 Path2 -MPc --check-access --max-delete 10 --filters-file /path/to/filters.txt -v --check-sync=false --no-cleanup --ignore-listing-checksum --disable ListR --checkers=16 --drive-pacer-min-sleep=10ms --create-empty-src-dirs --resilient
-```
-
-2. Periodic independent integrity check (perhaps scheduled nightly or weekly):
-
-```
-rclone check -MvPc Path1 Path2 --filter-from /path/to/filters.txt
-```
-
-3. If diffs are found, you have some choices to correct them. 
-If one side is more up-to-date and you want to make the other side match it, you could run:
-
-```
-rclone sync Path1 Path2 --filter-from /path/to/filters.txt --create-empty-src-dirs -MPc -v  
-```
-(or switch Path1 and Path2 to make Path2 the source-of-truth)
-
-Or, if neither side is totally up-to-date, you could run a `--resync` to bring them back into agreement 
-(but remember that this could cause deleted files to re-appear.)
-
-*Note also that `rclone check` does not currently include empty directories, 
-so if you want to know if any empty directories are out of sync, 
-consider alternatively running the above `rclone sync` command with `--dry-run` added.
 
 ### Empty directories
 
@@ -1273,6 +1272,8 @@ about _Unison_ and synchronization in general.
 * Copies and deletes are now handled in one operation instead of two
 * `--track-renames` and `--backup-dir` are now supported
 * Partial uploads known issue on `local`/`ftp`/`sftp` has been resolved (unless using `--inplace`)
+* Final listings are now generated from sync results, to avoid needing to re-list
+* Bisync is now much more resilient to changes that happen during a bisync run, and far less prone to critical errors / undetected changes
 
 ### `v1.64`
 * Fixed an [issue](https://forum.rclone.org/t/bisync-bugs-and-feature-requests/37636#:~:text=1.%20Dry%20runs%20are%20not%20completely%20dry)