Merge pull request #2415 from calmh/dbkeys

Add database and transaction instances

lib/db/leveldb.go

@@ -89,9 +89,18 @@ type dbReader interface {
 	Get([]byte, *opt.ReadOptions) ([]byte, error)
 }
 
-type dbWriter interface {
-	Put([]byte, []byte)
-	Delete([]byte)
+type dbInstance struct {
+	*leveldb.DB
+}
+
+type readOnlyTransaction struct {
+	*leveldb.Snapshot
+	db *leveldb.DB
+}
+
+type readWriteTransaction struct {
+	readOnlyTransaction
+	*leveldb.Batch
 }
 
 // Flush batches to disk when they contain this many records.
@@ -166,27 +175,57 @@ func globalKeyFolder(key []byte) []byte {
 	return folder[:izero]
 }
 
-type deletionHandler func(db dbReader, batch dbWriter, folder, device, name []byte, dbi iterator.Iterator) int64
+type deletionHandler func(t readWriteTransaction, folder, device, name []byte, dbi iterator.Iterator) int64
+
+func (db *dbInstance) newReadOnlyTransaction() readOnlyTransaction {
+	snap, err := db.GetSnapshot()
+	if err != nil {
+		panic(err)
+	}
+	return readOnlyTransaction{
+		Snapshot: snap,
+		db:       db.DB,
+	}
+}
+
+func (db *dbInstance) newReadWriteTransaction() readWriteTransaction {
+	t := db.newReadOnlyTransaction()
+	return readWriteTransaction{
+		readOnlyTransaction: t,
+		Batch:               new(leveldb.Batch),
+	}
+}
+
+func (t readOnlyTransaction) close() {
+	t.Release()
+}
+
+func (t readWriteTransaction) close() {
+	if err := t.db.Write(t.Batch, nil); err != nil {
+		panic(err)
+	}
+	t.readOnlyTransaction.close()
+}
 
-func ldbGenericReplace(db *leveldb.DB, folder, device []byte, fs []protocol.FileInfo, localSize, globalSize *sizeTracker, deleteFn deletionHandler) int64 {
+func (t readWriteTransaction) checkFlush() {
+	if t.Batch.Len() > batchFlushSize {
+		if err := t.db.Write(t.Batch, nil); err != nil {
+			panic(err)
+		}
+		t.Batch.Reset()
+	}
+}
+
+func (db *dbInstance) genericReplace(folder, device []byte, fs []protocol.FileInfo, localSize, globalSize *sizeTracker, deleteFn deletionHandler) int64 {
 	sort.Sort(fileList(fs)) // sort list on name, same as in the database
 
 	start := deviceKey(folder, device, nil)                            // before all folder/device files
 	limit := deviceKey(folder, device, []byte{0xff, 0xff, 0xff, 0xff}) // after all folder/device files
 
-	batch := new(leveldb.Batch)
-	l.Debugf("new batch %p", batch)
-	snap, err := db.GetSnapshot()
-	if err != nil {
-		panic(err)
-	}
-	l.Debugf("created snapshot %p", snap)
-	defer func() {
-		l.Debugf("close snapshot %p", snap)
-		snap.Release()
-	}()
+	t := db.newReadWriteTransaction()
+	defer t.close()
 
-	dbi := snap.NewIterator(&util.Range{Start: start, Limit: limit}, nil)
+	dbi := t.NewIterator(&util.Range{Start: start, Limit: limit}, nil)
 	defer dbi.Release()
 
 	moreDb := dbi.Next()
@@ -218,16 +257,16 @@ func ldbGenericReplace(db *leveldb.DB, folder, device []byte, fs []protocol.File
 		case moreFs && (!moreDb || cmp == -1):
 			l.Debugln("generic replace; missing - insert")
 			// Database is missing this file. Insert it.
-			if lv := ldbInsert(batch, folder, device, fs[fsi]); lv > maxLocalVer {
+			if lv := t.insertFile(folder, device, fs[fsi]); lv > maxLocalVer {
 				maxLocalVer = lv
 			}
 			if isLocalDevice {
 				localSize.addFile(fs[fsi])
 			}
 			if fs[fsi].IsInvalid() {
-				ldbRemoveFromGlobal(snap, batch, folder, device, newName, globalSize)
+				t.removeFromGlobal(folder, device, newName, globalSize)
 			} else {
-				ldbUpdateGlobal(snap, batch, folder, device, fs[fsi], globalSize)
+				t.updateGlobal(folder, device, fs[fsi], globalSize)
 			}
 			fsi++
 
@@ -240,7 +279,7 @@ func ldbGenericReplace(db *leveldb.DB, folder, device []byte, fs []protocol.File
 			ef.UnmarshalXDR(dbi.Value())
 			if !fs[fsi].Version.Equal(ef.Version) || fs[fsi].Flags != ef.Flags {
 				l.Debugln("generic replace; differs - insert")
-				if lv := ldbInsert(batch, folder, device, fs[fsi]); lv > maxLocalVer {
+				if lv := t.insertFile(folder, device, fs[fsi]); lv > maxLocalVer {
 					maxLocalVer = lv
 				}
 				if isLocalDevice {
@@ -248,9 +287,9 @@ func ldbGenericReplace(db *leveldb.DB, folder, device []byte, fs []protocol.File
 					localSize.addFile(fs[fsi])
 				}
 				if fs[fsi].IsInvalid() {
-					ldbRemoveFromGlobal(snap, batch, folder, device, newName, globalSize)
+					t.removeFromGlobal(folder, device, newName, globalSize)
 				} else {
-					ldbUpdateGlobal(snap, batch, folder, device, fs[fsi], globalSize)
+					t.updateGlobal(folder, device, fs[fsi], globalSize)
 				}
 			} else {
 				l.Debugln("generic replace; equal - ignore")
@@ -261,7 +300,7 @@ func ldbGenericReplace(db *leveldb.DB, folder, device []byte, fs []protocol.File
 
 		case moreDb && (!moreFs || cmp == 1):
 			l.Debugln("generic replace; exists - remove")
-			if lv := deleteFn(snap, batch, folder, device, oldName, dbi); lv > maxLocalVer {
+			if lv := deleteFn(t, folder, device, oldName, dbi); lv > maxLocalVer {
 				maxLocalVer = lv
 			}
 			moreDb = dbi.Next()
@@ -269,51 +308,26 @@ func ldbGenericReplace(db *leveldb.DB, folder, device []byte, fs []protocol.File
 
 		// Write out and reuse the batch every few records, to avoid the batch
 		// growing too large and thus allocating unnecessarily much memory.
-		if batch.Len() > batchFlushSize {
-			l.Debugf("db.Write %p", batch)
-
-			err = db.Write(batch, nil)
-			if err != nil {
-				panic(err)
-			}
-
-			batch.Reset()
-		}
-	}
-
-	l.Debugf("db.Write %p", batch)
-	err = db.Write(batch, nil)
-	if err != nil {
-		panic(err)
+		t.checkFlush()
 	}
 
 	return maxLocalVer
 }
 
-func ldbReplace(db *leveldb.DB, folder, device []byte, fs []protocol.FileInfo, localSize, globalSize *sizeTracker) int64 {
+func (db *dbInstance) replace(folder, device []byte, fs []protocol.FileInfo, localSize, globalSize *sizeTracker) int64 {
 	// TODO: Return the remaining maxLocalVer?
-	return ldbGenericReplace(db, folder, device, fs, localSize, globalSize, func(db dbReader, batch dbWriter, folder, device, name []byte, dbi iterator.Iterator) int64 {
+	return db.genericReplace(folder, device, fs, localSize, globalSize, func(t readWriteTransaction, folder, device, name []byte, dbi iterator.Iterator) int64 {
 		// Database has a file that we are missing. Remove it.
 		l.Debugf("delete; folder=%q device=%v name=%q", folder, protocol.DeviceIDFromBytes(device), name)
-		ldbRemoveFromGlobal(db, batch, folder, device, name, globalSize)
-		l.Debugf("batch.Delete %p %x", batch, dbi.Key())
-		batch.Delete(dbi.Key())
+		t.removeFromGlobal(folder, device, name, globalSize)
+		t.Delete(dbi.Key())
 		return 0
 	})
 }
 
-func ldbUpdate(db *leveldb.DB, folder, device []byte, fs []protocol.FileInfo, localSize, globalSize *sizeTracker) int64 {
-	batch := new(leveldb.Batch)
-	l.Debugf("new batch %p", batch)
-	snap, err := db.GetSnapshot()
-	if err != nil {
-		panic(err)
-	}
-	l.Debugf("created snapshot %p", snap)
-	defer func() {
-		l.Debugf("close snapshot %p", snap)
-		snap.Release()
-	}()
+func (db *dbInstance) updateFiles(folder, device []byte, fs []protocol.FileInfo, localSize, globalSize *sizeTracker) int64 {
+	t := db.newReadWriteTransaction()
+	defer t.close()
 
 	var maxLocalVer int64
 	var fk []byte
@@ -321,20 +335,19 @@ func ldbUpdate(db *leveldb.DB, folder, device []byte, fs []protocol.FileInfo, lo
 	for _, f := range fs {
 		name := []byte(f.Name)
 		fk = deviceKeyInto(fk[:cap(fk)], folder, device, name)
-		l.Debugf("snap.Get %p %x", snap, fk)
-		bs, err := snap.Get(fk, nil)
+		bs, err := t.Get(fk, nil)
 		if err == leveldb.ErrNotFound {
 			if isLocalDevice {
 				localSize.addFile(f)
 			}
 
-			if lv := ldbInsert(batch, folder, device, f); lv > maxLocalVer {
+			if lv := t.insertFile(folder, device, f); lv > maxLocalVer {
 				maxLocalVer = lv
 			}
 			if f.IsInvalid() {
-				ldbRemoveFromGlobal(snap, batch, folder, device, name, globalSize)
+				t.removeFromGlobal(folder, device, name, globalSize)
 			} else {
-				ldbUpdateGlobal(snap, batch, folder, device, f, globalSize)
+				t.updateGlobal(folder, device, f, globalSize)
 			}
 			continue
 		}
@@ -352,40 +365,25 @@ func ldbUpdate(db *leveldb.DB, folder, device []byte, fs []protocol.FileInfo, lo
 				localSize.addFile(f)
 			}
 
-			if lv := ldbInsert(batch, folder, device, f); lv > maxLocalVer {
+			if lv := t.insertFile(folder, device, f); lv > maxLocalVer {
 				maxLocalVer = lv
 			}
 			if f.IsInvalid() {
-				ldbRemoveFromGlobal(snap, batch, folder, device, name, globalSize)
+				t.removeFromGlobal(folder, device, name, globalSize)
 			} else {
-				ldbUpdateGlobal(snap, batch, folder, device, f, globalSize)
+				t.updateGlobal(folder, device, f, globalSize)
 			}
 		}
 
 		// Write out and reuse the batch every few records, to avoid the batch
 		// growing too large and thus allocating unnecessarily much memory.
-		if batch.Len() > batchFlushSize {
-			l.Debugf("db.Write %p", batch)
-
-			err = db.Write(batch, nil)
-			if err != nil {
-				panic(err)
-			}
-
-			batch.Reset()
-		}
-	}
-
-	l.Debugf("db.Write %p", batch)
-	err = db.Write(batch, nil)
-	if err != nil {
-		panic(err)
+		t.checkFlush()
 	}
 
 	return maxLocalVer
 }
 
-func ldbInsert(batch dbWriter, folder, device []byte, file protocol.FileInfo) int64 {
+func (t readWriteTransaction) insertFile(folder, device []byte, file protocol.FileInfo) int64 {
 	l.Debugf("insert; folder=%q device=%v %v", folder, protocol.DeviceIDFromBytes(device), file)
 
 	if file.LocalVersion == 0 {
@@ -394,20 +392,19 @@ func ldbInsert(batch dbWriter, folder, device []byte, file protocol.FileInfo) in
 
 	name := []byte(file.Name)
 	nk := deviceKey(folder, device, name)
-	l.Debugf("batch.Put %p %x", batch, nk)
-	batch.Put(nk, file.MustMarshalXDR())
+	t.Put(nk, file.MustMarshalXDR())
 
 	return file.LocalVersion
 }
 
-// ldbUpdateGlobal adds this device+version to the version list for the given
+// updateGlobal adds this device+version to the version list for the given
 // file. If the device is already present in the list, the version is updated.
 // If the file does not have an entry in the global list, it is created.
-func ldbUpdateGlobal(db dbReader, batch dbWriter, folder, device []byte, file protocol.FileInfo, globalSize *sizeTracker) bool {
+func (t readWriteTransaction) updateGlobal(folder, device []byte, file protocol.FileInfo, globalSize *sizeTracker) bool {
 	l.Debugf("update global; folder=%q device=%v file=%q version=%d", folder, protocol.DeviceIDFromBytes(device), file.Name, file.Version)
 	name := []byte(file.Name)
 	gk := globalKey(folder, name)
-	svl, err := db.Get(gk, nil)
+	svl, err := t.Get(gk, nil)
 	if err != nil && err != leveldb.ErrNotFound {
 		panic(err)
 	}
@@ -432,7 +429,7 @@ func ldbUpdateGlobal(db dbReader, batch dbWriter, folder, device []byte, file pr
 				if i == 0 {
 					// Keep the current newest file around so we can subtract it from
 					// the globalSize if we replace it.
-					oldFile, hasOldFile = ldbGet(db, folder, fl.versions[0].device, name)
+					oldFile, hasOldFile = t.getFile(folder, fl.versions[0].device, name)
 				}
 
 				fl.versions = append(fl.versions[:i], fl.versions[i+1:]...)
@@ -465,7 +462,7 @@ func ldbUpdateGlobal(db dbReader, batch dbWriter, folder, device []byte, file pr
 			// "Greater" in the condition above is just based on the device
 			// IDs in the version vector, which is not the only thing we use
 			// to determine the winner.)
-			of, ok := ldbGet(db, folder, fl.versions[i].device, name)
+			of, ok := t.getFile(folder, fl.versions[i].device, name)
 			if !ok {
 				panic("file referenced in version list does not exist")
 			}
@@ -492,7 +489,7 @@ done:
 				globalSize.removeFile(oldFile)
 			} else if len(fl.versions) > 1 {
 				// The previous newest version is now at index 1, grab it from there.
-				oldFile, ok := ldbGet(db, folder, fl.versions[1].device, name)
+				oldFile, ok := t.getFile(folder, fl.versions[1].device, name)
 				if !ok {
 					panic("file referenced in version list does not exist")
 				}
@@ -501,9 +498,8 @@ done:
 		}
 	}
 
-	l.Debugf("batch.Put %p %x", batch, gk)
 	l.Debugf("new global after update: %v", fl)
-	batch.Put(gk, fl.MustMarshalXDR())
+	t.Put(gk, fl.MustMarshalXDR())
 
 	return true
 }
@@ -518,11 +514,11 @@ func insertVersion(vl []fileVersion, i int, v fileVersion) []fileVersion {
 // ldbRemoveFromGlobal removes the device from the global version list for the
 // given file. If the version list is empty after this, the file entry is
 // removed entirely.
-func ldbRemoveFromGlobal(db dbReader, batch dbWriter, folder, device, file []byte, globalSize *sizeTracker) {
+func (t readWriteTransaction) removeFromGlobal(folder, device, file []byte, globalSize *sizeTracker) {
 	l.Debugf("remove from global; folder=%q device=%v file=%q", folder, protocol.DeviceIDFromBytes(device), file)
 
 	gk := globalKey(folder, file)
-	svl, err := db.Get(gk, nil)
+	svl, err := t.Get(gk, nil)
 	if err != nil {
 		// We might be called to "remove" a global version that doesn't exist
 		// if the first update for the file is already marked invalid.
@@ -539,7 +535,7 @@ func ldbRemoveFromGlobal(db dbReader, batch dbWriter, folder, device, file []byt
 	for i := range fl.versions {
 		if bytes.Compare(fl.versions[i].device, device) == 0 {
 			if i == 0 && globalSize != nil {
-				f, ok := ldbGet(db, folder, device, file)
+				f, ok := t.getFile(folder, device, file)
 				if !ok {
 					panic("removing nonexistent file")
 				}
@@ -552,14 +548,12 @@ func ldbRemoveFromGlobal(db dbReader, batch dbWriter, folder, device, file []byt
 	}
 
 	if len(fl.versions) == 0 {
-		l.Debugf("batch.Delete %p %x", batch, gk)
-		batch.Delete(gk)
+		t.Delete(gk)
 	} else {
-		l.Debugf("batch.Put %p %x", batch, gk)
 		l.Debugf("new global after remove: %v", fl)
-		batch.Put(gk, fl.MustMarshalXDR())
+		t.Put(gk, fl.MustMarshalXDR())
 		if removed {
-			f, ok := ldbGet(db, folder, fl.versions[0].device, file)
+			f, ok := t.getFile(folder, fl.versions[0].device, file)
 			if !ok {
 				panic("new global is nonexistent file")
 			}
@@ -568,20 +562,14 @@ func ldbRemoveFromGlobal(db dbReader, batch dbWriter, folder, device, file []byt
 	}
 }
 
-func ldbWithHave(db *leveldb.DB, folder, device []byte, truncate bool, fn Iterator) {
+func (db *dbInstance) withHave(folder, device []byte, truncate bool, fn Iterator) {
 	start := deviceKey(folder, device, nil)                            // before all folder/device files
 	limit := deviceKey(folder, device, []byte{0xff, 0xff, 0xff, 0xff}) // after all folder/device files
-	snap, err := db.GetSnapshot()
-	if err != nil {
-		panic(err)
-	}
-	l.Debugf("created snapshot %p", snap)
-	defer func() {
-		l.Debugf("close snapshot %p", snap)
-		snap.Release()
-	}()
 
-	dbi := snap.NewIterator(&util.Range{Start: start, Limit: limit}, nil)
+	t := db.newReadOnlyTransaction()
+	defer t.close()
+
+	dbi := t.NewIterator(&util.Range{Start: start, Limit: limit}, nil)
 	defer dbi.Release()
 
 	for dbi.Next() {
@@ -595,20 +583,14 @@ func ldbWithHave(db *leveldb.DB, folder, device []byte, truncate bool, fn Iterat
 	}
 }
 
-func ldbWithAllFolderTruncated(db *leveldb.DB, folder []byte, fn func(device []byte, f FileInfoTruncated) bool) {
+func (db *dbInstance) withAllFolderTruncated(folder []byte, fn func(device []byte, f FileInfoTruncated) bool) {
 	start := deviceKey(folder, nil, nil)                                                  // before all folder/device files
 	limit := deviceKey(folder, protocol.LocalDeviceID[:], []byte{0xff, 0xff, 0xff, 0xff}) // after all folder/device files
-	snap, err := db.GetSnapshot()
-	if err != nil {
-		panic(err)
-	}
-	l.Debugf("created snapshot %p", snap)
-	defer func() {
-		l.Debugf("close snapshot %p", snap)
-		snap.Release()
-	}()
 
-	dbi := snap.NewIterator(&util.Range{Start: start, Limit: limit}, nil)
+	t := db.newReadWriteTransaction()
+	defer t.close()
+
+	dbi := t.NewIterator(&util.Range{Start: start, Limit: limit}, nil)
 	defer dbi.Release()
 
 	for dbi.Next() {
@@ -622,10 +604,9 @@ func ldbWithAllFolderTruncated(db *leveldb.DB, folder []byte, fn func(device []b
 		switch f.Name {
 		case "", ".", "..", "/": // A few obviously invalid filenames
 			l.Infof("Dropping invalid filename %q from database", f.Name)
-			batch := new(leveldb.Batch)
-			ldbRemoveFromGlobal(db, batch, folder, device, nil, nil)
-			batch.Delete(dbi.Key())
-			db.Write(batch, nil)
+			t.removeFromGlobal(folder, device, nil, nil)
+			t.Delete(dbi.Key())
+			t.checkFlush()
 			continue
 		}
 
@@ -635,7 +616,15 @@ func ldbWithAllFolderTruncated(db *leveldb.DB, folder []byte, fn func(device []b
 	}
 }
 
-func ldbGet(db dbReader, folder, device, file []byte) (protocol.FileInfo, bool) {
+func (db *dbInstance) getFile(folder, device, file []byte) (protocol.FileInfo, bool) {
+	return ldbGetFile(db, folder, device, file)
+}
+
+func (t readOnlyTransaction) getFile(folder, device, file []byte) (protocol.FileInfo, bool) {
+	return ldbGetFile(t, folder, device, file)
+}
+
+func ldbGetFile(db dbReader, folder, device, file []byte) (protocol.FileInfo, bool) {
 	nk := deviceKey(folder, device, file)
 	bs, err := db.Get(nk, nil)
 	if err == leveldb.ErrNotFound {
@@ -653,20 +642,13 @@ func ldbGet(db dbReader, folder, device, file []byte) (protocol.FileInfo, bool)
 	return f, true
 }
 
-func ldbGetGlobal(db *leveldb.DB, folder, file []byte, truncate bool) (FileIntf, bool) {
+func (db *dbInstance) getGlobal(folder, file []byte, truncate bool) (FileIntf, bool) {
 	k := globalKey(folder, file)
-	snap, err := db.GetSnapshot()
-	if err != nil {
-		panic(err)
-	}
-	l.Debugf("created snapshot %p", snap)
-	defer func() {
-		l.Debugf("close snapshot %p", snap)
-		snap.Release()
-	}()
 
-	l.Debugf("snap.Get %p %x", snap, k)
-	bs, err := snap.Get(k, nil)
+	t := db.newReadOnlyTransaction()
+	defer t.close()
+
+	bs, err := t.Get(k, nil)
 	if err == leveldb.ErrNotFound {
 		return nil, false
 	}
@@ -685,8 +667,7 @@ func ldbGetGlobal(db *leveldb.DB, folder, file []byte, truncate bool) (FileIntf,
 	}
 
 	k = deviceKey(folder, vl.versions[0].device, file)
-	l.Debugf("snap.Get %p %x", snap, k)
-	bs, err = snap.Get(k, nil)
+	bs, err = t.Get(k, nil)
 	if err != nil {
 		panic(err)
 	}
@@ -698,18 +679,11 @@ func ldbGetGlobal(db *leveldb.DB, folder, file []byte, truncate bool) (FileIntf,
 	return fi, true
 }
 
-func ldbWithGlobal(db *leveldb.DB, folder, prefix []byte, truncate bool, fn Iterator) {
-	snap, err := db.GetSnapshot()
-	if err != nil {
-		panic(err)
-	}
-	l.Debugf("created snapshot %p", snap)
-	defer func() {
-		l.Debugf("close snapshot %p", snap)
-		snap.Release()
-	}()
+func (db *dbInstance) withGlobal(folder, prefix []byte, truncate bool, fn Iterator) {
+	t := db.newReadOnlyTransaction()
+	defer t.close()
 
-	dbi := snap.NewIterator(util.BytesPrefix(globalKey(folder, prefix)), nil)
+	dbi := t.NewIterator(util.BytesPrefix(globalKey(folder, prefix)), nil)
 	defer dbi.Release()
 
 	var fk []byte
@@ -725,8 +699,7 @@ func ldbWithGlobal(db *leveldb.DB, folder, prefix []byte, truncate bool, fn Iter
 		}
 		name := globalKeyName(dbi.Key())
 		fk = deviceKeyInto(fk[:cap(fk)], folder, vl.versions[0].device, name)
-		l.Debugf("snap.Get %p %x", snap, fk)
-		bs, err := snap.Get(fk, nil)
+		bs, err := t.Get(fk, nil)
 		if err != nil {
 			l.Debugf("folder: %q (%x)", folder, folder)
 			l.Debugf("key: %q (%x)", dbi.Key(), dbi.Key())
@@ -749,7 +722,7 @@ func ldbWithGlobal(db *leveldb.DB, folder, prefix []byte, truncate bool, fn Iter
 	}
 }
 
-func ldbAvailability(db *leveldb.DB, folder, file []byte) []protocol.DeviceID {
+func (db *dbInstance) availability(folder, file []byte) []protocol.DeviceID {
 	k := globalKey(folder, file)
 	bs, err := db.Get(k, nil)
 	if err == leveldb.ErrNotFound {
@@ -777,20 +750,14 @@ func ldbAvailability(db *leveldb.DB, folder, file []byte) []protocol.DeviceID {
 	return devices
 }
 
-func ldbWithNeed(db *leveldb.DB, folder, device []byte, truncate bool, fn Iterator) {
+func (db *dbInstance) withNeed(folder, device []byte, truncate bool, fn Iterator) {
 	start := globalKey(folder, nil)
 	limit := globalKey(folder, []byte{0xff, 0xff, 0xff, 0xff})
-	snap, err := db.GetSnapshot()
-	if err != nil {
-		panic(err)
-	}
-	l.Debugf("created snapshot %p", snap)
-	defer func() {
-		l.Debugf("close snapshot %p", snap)
-		snap.Release()
-	}()
 
-	dbi := snap.NewIterator(&util.Range{Start: start, Limit: limit}, nil)
+	t := db.newReadOnlyTransaction()
+	defer t.close()
+
+	dbi := t.NewIterator(&util.Range{Start: start, Limit: limit}, nil)
 	defer dbi.Release()
 
 	var fk []byte
@@ -832,8 +799,7 @@ nextFile:
 					continue nextFile
 				}
 				fk = deviceKeyInto(fk[:cap(fk)], folder, vl.versions[i].device, name)
-				l.Debugf("snap.Get %p %x", snap, fk)
-				bs, err := snap.Get(fk, nil)
+				bs, err := t.Get(fk, nil)
 				if err != nil {
 					var id protocol.DeviceID
 					copy(id[:], device)
@@ -875,18 +841,11 @@ nextFile:
 	}
 }
 
-func ldbListFolders(db *leveldb.DB) []string {
-	snap, err := db.GetSnapshot()
-	if err != nil {
-		panic(err)
-	}
-	l.Debugf("created snapshot %p", snap)
-	defer func() {
-		l.Debugf("close snapshot %p", snap)
-		snap.Release()
-	}()
+func (db *dbInstance) listFolders() []string {
+	t := db.newReadOnlyTransaction()
+	defer t.close()
 
-	dbi := snap.NewIterator(util.BytesPrefix([]byte{KeyTypeGlobal}), nil)
+	dbi := t.NewIterator(util.BytesPrefix([]byte{KeyTypeGlobal}), nil)
 	defer dbi.Release()
 
 	folderExists := make(map[string]bool)
@@ -906,19 +865,12 @@ func ldbListFolders(db *leveldb.DB) []string {
 	return folders
 }
 
-func ldbDropFolder(db *leveldb.DB, folder []byte) {
-	snap, err := db.GetSnapshot()
-	if err != nil {
-		panic(err)
-	}
-	l.Debugf("created snapshot %p", snap)
-	defer func() {
-		l.Debugf("close snapshot %p", snap)
-		snap.Release()
-	}()
+func (db *dbInstance) dropFolder(folder []byte) {
+	t := db.newReadOnlyTransaction()
+	defer t.close()
 
 	// Remove all items related to the given folder from the device->file bucket
-	dbi := snap.NewIterator(util.BytesPrefix([]byte{KeyTypeDevice}), nil)
+	dbi := t.NewIterator(util.BytesPrefix([]byte{KeyTypeDevice}), nil)
 	for dbi.Next() {
 		itemFolder := deviceKeyFolder(dbi.Key())
 		if bytes.Compare(folder, itemFolder) == 0 {
@@ -928,7 +880,7 @@ func ldbDropFolder(db *leveldb.DB, folder []byte) {
 	dbi.Release()
 
 	// Remove all items related to the given folder from the global bucket
-	dbi = snap.NewIterator(util.BytesPrefix([]byte{KeyTypeGlobal}), nil)
+	dbi = t.NewIterator(util.BytesPrefix([]byte{KeyTypeGlobal}), nil)
 	for dbi.Next() {
 		itemFolder := globalKeyFolder(dbi.Key())
 		if bytes.Compare(folder, itemFolder) == 0 {
@@ -950,25 +902,15 @@ func unmarshalTrunc(bs []byte, truncate bool) (FileIntf, error) {
 	return tf, err
 }
 
-func ldbCheckGlobals(db *leveldb.DB, folder []byte, globalSize *sizeTracker) {
-	snap, err := db.GetSnapshot()
-	if err != nil {
-		panic(err)
-	}
-	l.Debugf("created snapshot %p", snap)
-	defer func() {
-		l.Debugf("close snapshot %p", snap)
-		snap.Release()
-	}()
+func (db *dbInstance) checkGlobals(folder []byte, globalSize *sizeTracker) {
+	t := db.newReadWriteTransaction()
+	defer t.close()
 
 	start := globalKey(folder, nil)
 	limit := globalKey(folder, []byte{0xff, 0xff, 0xff, 0xff})
-	dbi := snap.NewIterator(&util.Range{Start: start, Limit: limit}, nil)
+	dbi := t.NewIterator(&util.Range{Start: start, Limit: limit}, nil)
 	defer dbi.Release()
 
-	batch := new(leveldb.Batch)
-	l.Debugf("new batch %p", batch)
-
 	var fk []byte
 	for dbi.Next() {
 		gk := dbi.Key()
@@ -988,8 +930,7 @@ func ldbCheckGlobals(db *leveldb.DB, folder []byte, globalSize *sizeTracker) {
 		for i, version := range vl.versions {
 			fk = deviceKeyInto(fk[:cap(fk)], folder, version.device, name)
 
-			l.Debugf("snap.Get %p %x", snap, fk)
-			_, err := snap.Get(fk, nil)
+			_, err := t.Get(fk, nil)
 			if err == leveldb.ErrNotFound {
 				continue
 			}
@@ -999,7 +940,7 @@ func ldbCheckGlobals(db *leveldb.DB, folder []byte, globalSize *sizeTracker) {
 			newVL.versions = append(newVL.versions, version)
 
 			if i == 0 {
-				fi, ok := ldbGet(snap, folder, version.device, name)
+				fi, ok := t.getFile(folder, version.device, name)
 				if !ok {
 					panic("nonexistent global master file")
 				}
@@ -1008,10 +949,9 @@ func ldbCheckGlobals(db *leveldb.DB, folder []byte, globalSize *sizeTracker) {
 		}
 
 		if len(newVL.versions) != len(vl.versions) {
-			l.Infof("db repair: rewriting global version list for %x %x", gk[1:1+64], gk[1+64:])
-			batch.Put(dbi.Key(), newVL.MustMarshalXDR())
+			t.Put(dbi.Key(), newVL.MustMarshalXDR())
+			t.checkFlush()
 		}
 	}
 	l.Debugf("db check completed for %q", folder)
-	db.Write(batch, nil)
 }

lib/db/set.go

@@ -25,7 +25,7 @@ type FileSet struct {
 	localVersion map[protocol.DeviceID]int64
 	mutex        sync.Mutex
 	folder       string
-	db           *leveldb.DB
+	db           *dbInstance
 	blockmap     *BlockMap
 	localSize    sizeTracker
 	globalSize   sizeTracker
@@ -97,15 +97,15 @@ func NewFileSet(folder string, db *leveldb.DB) *FileSet {
 	var s = FileSet{
 		localVersion: make(map[protocol.DeviceID]int64),
 		folder:       folder,
-		db:           db,
+		db:           &dbInstance{db},
 		blockmap:     NewBlockMap(db, folder),
 		mutex:        sync.NewMutex(),
 	}
 
-	ldbCheckGlobals(db, []byte(folder), &s.globalSize)
+	s.db.checkGlobals([]byte(folder), &s.globalSize)
 
 	var deviceID protocol.DeviceID
-	ldbWithAllFolderTruncated(db, []byte(folder), func(device []byte, f FileInfoTruncated) bool {
+	s.db.withAllFolderTruncated([]byte(folder), func(device []byte, f FileInfoTruncated) bool {
 		copy(deviceID[:], device)
 		if f.LocalVersion > s.localVersion[deviceID] {
 			s.localVersion[deviceID] = f.LocalVersion
@@ -126,7 +126,7 @@ func (s *FileSet) Replace(device protocol.DeviceID, fs []protocol.FileInfo) {
 	normalizeFilenames(fs)
 	s.mutex.Lock()
 	defer s.mutex.Unlock()
-	s.localVersion[device] = ldbReplace(s.db, []byte(s.folder), device[:], fs, &s.localSize, &s.globalSize)
+	s.localVersion[device] = s.db.replace([]byte(s.folder), device[:], fs, &s.localSize, &s.globalSize)
 	if len(fs) == 0 {
 		// Reset the local version if all files were removed.
 		s.localVersion[device] = 0
@@ -146,7 +146,7 @@ func (s *FileSet) Update(device protocol.DeviceID, fs []protocol.FileInfo) {
 		discards := make([]protocol.FileInfo, 0, len(fs))
 		updates := make([]protocol.FileInfo, 0, len(fs))
 		for _, newFile := range fs {
-			existingFile, ok := ldbGet(s.db, []byte(s.folder), device[:], []byte(newFile.Name))
+			existingFile, ok := s.db.getFile([]byte(s.folder), device[:], []byte(newFile.Name))
 			if !ok || !existingFile.Version.Equal(newFile.Version) {
 				discards = append(discards, existingFile)
 				updates = append(updates, newFile)
@@ -155,54 +155,54 @@ func (s *FileSet) Update(device protocol.DeviceID, fs []protocol.FileInfo) {
 		s.blockmap.Discard(discards)
 		s.blockmap.Update(updates)
 	}
-	if lv := ldbUpdate(s.db, []byte(s.folder), device[:], fs, &s.localSize, &s.globalSize); lv > s.localVersion[device] {
+	if lv := s.db.updateFiles([]byte(s.folder), device[:], fs, &s.localSize, &s.globalSize); lv > s.localVersion[device] {
 		s.localVersion[device] = lv
 	}
 }
 
 func (s *FileSet) WithNeed(device protocol.DeviceID, fn Iterator) {
 	l.Debugf("%s WithNeed(%v)", s.folder, device)
-	ldbWithNeed(s.db, []byte(s.folder), device[:], false, nativeFileIterator(fn))
+	s.db.withNeed([]byte(s.folder), device[:], false, nativeFileIterator(fn))
 }
 
 func (s *FileSet) WithNeedTruncated(device protocol.DeviceID, fn Iterator) {
 	l.Debugf("%s WithNeedTruncated(%v)", s.folder, device)
-	ldbWithNeed(s.db, []byte(s.folder), device[:], true, nativeFileIterator(fn))
+	s.db.withNeed([]byte(s.folder), device[:], true, nativeFileIterator(fn))
 }
 
 func (s *FileSet) WithHave(device protocol.DeviceID, fn Iterator) {
 	l.Debugf("%s WithHave(%v)", s.folder, device)
-	ldbWithHave(s.db, []byte(s.folder), device[:], false, nativeFileIterator(fn))
+	s.db.withHave([]byte(s.folder), device[:], false, nativeFileIterator(fn))
 }
 
 func (s *FileSet) WithHaveTruncated(device protocol.DeviceID, fn Iterator) {
 	l.Debugf("%s WithHaveTruncated(%v)", s.folder, device)
-	ldbWithHave(s.db, []byte(s.folder), device[:], true, nativeFileIterator(fn))
+	s.db.withHave([]byte(s.folder), device[:], true, nativeFileIterator(fn))
 }
 
 func (s *FileSet) WithGlobal(fn Iterator) {
 	l.Debugf("%s WithGlobal()", s.folder)
-	ldbWithGlobal(s.db, []byte(s.folder), nil, false, nativeFileIterator(fn))
+	s.db.withGlobal([]byte(s.folder), nil, false, nativeFileIterator(fn))
 }
 
 func (s *FileSet) WithGlobalTruncated(fn Iterator) {
 	l.Debugf("%s WithGlobalTruncated()", s.folder)
-	ldbWithGlobal(s.db, []byte(s.folder), nil, true, nativeFileIterator(fn))
+	s.db.withGlobal([]byte(s.folder), nil, true, nativeFileIterator(fn))
 }
 
 func (s *FileSet) WithPrefixedGlobalTruncated(prefix string, fn Iterator) {
 	l.Debugf("%s WithPrefixedGlobalTruncated()", s.folder, prefix)
-	ldbWithGlobal(s.db, []byte(s.folder), []byte(osutil.NormalizedFilename(prefix)), true, nativeFileIterator(fn))
+	s.db.withGlobal([]byte(s.folder), []byte(osutil.NormalizedFilename(prefix)), true, nativeFileIterator(fn))
 }
 
 func (s *FileSet) Get(device protocol.DeviceID, file string) (protocol.FileInfo, bool) {
-	f, ok := ldbGet(s.db, []byte(s.folder), device[:], []byte(osutil.NormalizedFilename(file)))
+	f, ok := s.db.getFile([]byte(s.folder), device[:], []byte(osutil.NormalizedFilename(file)))
 	f.Name = osutil.NativeFilename(f.Name)
 	return f, ok
 }
 
 func (s *FileSet) GetGlobal(file string) (protocol.FileInfo, bool) {
-	fi, ok := ldbGetGlobal(s.db, []byte(s.folder), []byte(osutil.NormalizedFilename(file)), false)
+	fi, ok := s.db.getGlobal([]byte(s.folder), []byte(osutil.NormalizedFilename(file)), false)
 	if !ok {
 		return protocol.FileInfo{}, false
 	}
@@ -212,7 +212,7 @@ func (s *FileSet) GetGlobal(file string) (protocol.FileInfo, bool) {
 }
 
 func (s *FileSet) GetGlobalTruncated(file string) (FileInfoTruncated, bool) {
-	fi, ok := ldbGetGlobal(s.db, []byte(s.folder), []byte(osutil.NormalizedFilename(file)), true)
+	fi, ok := s.db.getGlobal([]byte(s.folder), []byte(osutil.NormalizedFilename(file)), true)
 	if !ok {
 		return FileInfoTruncated{}, false
 	}
@@ -222,7 +222,7 @@ func (s *FileSet) GetGlobalTruncated(file string) (FileInfoTruncated, bool) {
 }
 
 func (s *FileSet) Availability(file string) []protocol.DeviceID {
-	return ldbAvailability(s.db, []byte(s.folder), []byte(osutil.NormalizedFilename(file)))
+	return s.db.availability([]byte(s.folder), []byte(osutil.NormalizedFilename(file)))
 }
 
 func (s *FileSet) LocalVersion(device protocol.DeviceID) int64 {
@@ -241,13 +241,15 @@ func (s *FileSet) GlobalSize() (files, deleted int, bytes int64) {
 
 // ListFolders returns the folder IDs seen in the database.
 func ListFolders(db *leveldb.DB) []string {
-	return ldbListFolders(db)
+	i := &dbInstance{db}
+	return i.listFolders()
 }
 
 // DropFolder clears out all information related to the given folder from the
 // database.
 func DropFolder(db *leveldb.DB, folder string) {
-	ldbDropFolder(db, []byte(folder))
+	i := &dbInstance{db}
+	i.dropFolder([]byte(folder))
 	bm := &BlockMap{
 		db:     db,
 		folder: folder,