cryptfs: fix quota for overwrites if upload fails

Signed-off-by: Nicola Murino <nicola.murino@gmail.com>

go.mod

@@ -68,7 +68,7 @@ require (
 	golang.org/x/crypto v0.0.0-20221005025214-4161e89ecf1b
 	golang.org/x/net v0.0.0-20221004154528-8021a29435af
 	golang.org/x/oauth2 v0.0.0-20221006150949-b44042a4b9c1
-	golang.org/x/sys v0.0.0-20221006211917-84dc82d7e875
+	golang.org/x/sys v0.0.0-20221010170243-090e33056c14
 	golang.org/x/time v0.0.0-20220922220347-f3bd1da661af
 	google.golang.org/api v0.98.0
 	gopkg.in/natefinch/lumberjack.v2 v2.0.0
@@ -118,7 +118,7 @@ require (
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20200714003250-2b9c44734f2b // indirect
 	github.com/jmespath/go-jmespath v0.4.0 // indirect
-	github.com/klauspost/cpuid/v2 v2.1.1 // indirect
+	github.com/klauspost/cpuid/v2 v2.1.2 // indirect
 	github.com/kr/fs v0.1.0 // indirect
 	github.com/lestrrat-go/backoff/v2 v2.0.8 // indirect
 	github.com/lestrrat-go/blackmagic v1.0.1 // indirect
@@ -159,7 +159,7 @@ require (
 	golang.org/x/tools v0.1.12 // indirect
 	golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2 // indirect
 	google.golang.org/appengine v1.6.7 // indirect
-	google.golang.org/genproto v0.0.0-20220930163606-c98284e70a91 // indirect
+	google.golang.org/genproto v0.0.0-20221010155953-15ba04fc1c0e // indirect
 	google.golang.org/grpc v1.50.0 // indirect
 	google.golang.org/protobuf v1.28.1 // indirect
 	gopkg.in/ini.v1 v1.67.0 // indirect

go.sum

@@ -1064,8 +1064,8 @@ github.com/klauspost/compress v1.15.1/go.mod h1:/3/Vjq9QcHkK5uEr5lBEmyoZ1iFhe47e
 github.com/klauspost/compress v1.15.11 h1:Lcadnb3RKGin4FYM/orgq0qde+nc15E5Cbqg4B9Sx9c=
 github.com/klauspost/compress v1.15.11/go.mod h1:QPwzmACJjUTFsnSHH934V6woptycfrDDJnH7hvFVbGM=
 github.com/klauspost/cpuid/v2 v2.0.4/go.mod h1:FInQzS24/EEf25PyTYn52gqo7WaD8xa0213Md/qVLRg=
-github.com/klauspost/cpuid/v2 v2.1.1 h1:t0wUqjowdm8ezddV5k0tLWVklVuvLJpoHeb4WBdydm0=
+github.com/klauspost/cpuid/v2 v2.1.2 h1:XhdX4fqAJUA0yj+kUwMavO0hHrSPAecYdYf1ZmxHvak=
-github.com/klauspost/cpuid/v2 v2.1.1/go.mod h1:RVVoqg1df56z8g3pUjL/3lE5UfnlrJX8tyFgg4nqhuY=
+github.com/klauspost/cpuid/v2 v2.1.2/go.mod h1:RVVoqg1df56z8g3pUjL/3lE5UfnlrJX8tyFgg4nqhuY=
 github.com/kolo/xmlrpc v0.0.0-20201022064351-38db28db192b/go.mod h1:pcaDhQK0/NJZEvtCO0qQPPropqV0sJOJ6YW7X+9kRwM=
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/konsorten/go-windows-terminal-sequences v1.0.2/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
@@ -1916,8 +1916,8 @@ golang.org/x/sys v0.0.0-20220704084225-05e143d24a9e/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.0.0-20220728004956-3c1f35247d10/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220731174439-a90be440212d/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20221006211917-84dc82d7e875 h1:AzgQNqF+FKwyQ5LbVrVqOcuuFB67N47F9+htZYH0wFM=
+golang.org/x/sys v0.0.0-20221010170243-090e33056c14 h1:k5II8e6QD8mITdi+okbbmR/cIyEbeXLBhy5Ha4nevyc=
-golang.org/x/sys v0.0.0-20221006211917-84dc82d7e875/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20221010170243-090e33056c14/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.0.0-20210220032956-6a3ed077a48d/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.0.0-20210615171337-6886f2dfbf5b/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
@@ -2206,8 +2206,8 @@ google.golang.org/genproto v0.0.0-20220617124728-180714bec0ad/go.mod h1:KEWEmljW
 google.golang.org/genproto v0.0.0-20220624142145-8cd45d7dbd1f/go.mod h1:KEWEmljWE5zPzLBa/oHl6DaEt9LmfH6WtH1OHIvleBA=
 google.golang.org/genproto v0.0.0-20220628213854-d9e0b6570c03/go.mod h1:KEWEmljWE5zPzLBa/oHl6DaEt9LmfH6WtH1OHIvleBA=
 google.golang.org/genproto v0.0.0-20220802133213-ce4fa296bf78/go.mod h1:iHe1svFLAZg9VWz891+QbRMwUv9O/1Ww+/mngYeThbc=
-google.golang.org/genproto v0.0.0-20220930163606-c98284e70a91 h1:Ezh2cpcnP5Rq60sLensUsFnxh7P6513NLvNtCm9iyJ4=
+google.golang.org/genproto v0.0.0-20221010155953-15ba04fc1c0e h1:halCgTFuLWDRD61piiNSxPsARANGD3Xl16hPrLgLiIg=
-google.golang.org/genproto v0.0.0-20220930163606-c98284e70a91/go.mod h1:3526vdqwhZAwq4wsRUaVG555sVgsNmIjRtO7t/JH29U=
+google.golang.org/genproto v0.0.0-20221010155953-15ba04fc1c0e/go.mod h1:3526vdqwhZAwq4wsRUaVG555sVgsNmIjRtO7t/JH29U=
 google.golang.org/grpc v0.0.0-20160317175043-d3ddb4469d5a/go.mod h1:yo6s7OP7yaDglbqo1J04qKzAhqBH6lvTonzMVmEdcZw=
 google.golang.org/grpc v1.17.0/go.mod h1:6QZJwpn2B+Zp71q/5VxRsJ6NXXVCE5NRUHRo+f3cWCs=
 google.golang.org/grpc v1.19.0/go.mod h1:mqu4LbDTu4XGKhr4mRzUsmM4RtVoemTSY81AxZiDr8c=

internal/common/connection_test.go

@@ -37,10 +37,14 @@ import (
 type MockOsFs struct {
 	vfs.Fs
 	hasVirtualFolders bool
+	name              string
 }
 
 // Name returns the name for the Fs implementation
 func (fs *MockOsFs) Name() string {
+	if fs.name != "" {
+		return fs.name
+	}
 	return "mockOsFs"
 }
 
@@ -57,9 +61,10 @@ func (fs *MockOsFs) Chtimes(name string, atime, mtime time.Time, isUploading boo
 	return vfs.ErrVfsUnsupported
 }
 
-func newMockOsFs(hasVirtualFolders bool, connectionID, rootDir string) vfs.Fs {
+func newMockOsFs(hasVirtualFolders bool, connectionID, rootDir, name string) vfs.Fs {
 	return &MockOsFs{
 		Fs:                vfs.NewOsFs(connectionID, rootDir, ""),
+		name:              name,
 		hasVirtualFolders: hasVirtualFolders,
 	}
 }
@@ -108,7 +113,7 @@ func TestSetStatMode(t *testing.T) {
 	}
 	user.Permissions = make(map[string][]string)
 	user.Permissions["/"] = []string{dataprovider.PermAny}
-	fs := newMockOsFs(true, "", user.GetHomeDir())
+	fs := newMockOsFs(true, "", user.GetHomeDir(), "")
 	conn := NewBaseConnection("", ProtocolWebDAV, "", "", user)
 	err := conn.handleChmod(fs, fakePath, fakePath, nil)
 	assert.NoError(t, err)
@@ -429,7 +434,7 @@ func TestMaxWriteSize(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, int64(90), size)
 
-	fs = newMockOsFs(true, fs.ConnectionID(), user.GetHomeDir())
+	fs = newMockOsFs(true, fs.ConnectionID(), user.GetHomeDir(), "")
 	size, err = conn.GetMaxWriteSize(quotaResult, true, 100, fs.IsUploadResumeSupported())
 	assert.EqualError(t, err, ErrOpUnsupported.Error())
 	assert.Equal(t, int64(0), size)

internal/common/protocol_test.go

@@ -479,6 +479,71 @@ func TestSetStat(t *testing.T) {
 	assert.NoError(t, err)
 }
 
+func TestCryptFsUserUploadErrorOverwrite(t *testing.T) {
+	u := getCryptFsUser()
+	u.QuotaSize = 6000
+	user, _, err := httpdtest.AddUser(u, http.StatusCreated)
+	assert.NoError(t, err)
+	var buf []byte
+	for i := 0; i < 4000; i++ {
+		buf = append(buf, []byte("a")...)
+	}
+	bufSize := int64(len(buf))
+	reader := bytes.NewReader(buf)
+	conn, client, err := getSftpClient(user)
+	if assert.NoError(t, err) {
+		defer conn.Close()
+		defer client.Close()
+
+		f, err := client.Create(testFileName + "_big")
+		assert.NoError(t, err)
+		n, err := io.Copy(f, reader)
+		assert.NoError(t, err)
+		assert.Equal(t, bufSize, n)
+		err = f.Close()
+		assert.NoError(t, err)
+		encryptedSize, err := getEncryptedFileSize(bufSize)
+		assert.NoError(t, err)
+		expectedSize := encryptedSize
+		user, _, err = httpdtest.GetUserByUsername(user.Username, http.StatusOK)
+		assert.NoError(t, err)
+		assert.Equal(t, 1, user.UsedQuotaFiles)
+		assert.Equal(t, expectedSize, user.UsedQuotaSize)
+		// now write a small file
+		f, err = client.Create(testFileName)
+		assert.NoError(t, err)
+		_, err = f.Write(testFileContent)
+		assert.NoError(t, err)
+		err = f.Close()
+		assert.NoError(t, err)
+		encryptedSize, err = getEncryptedFileSize(int64(len(testFileContent)))
+		assert.NoError(t, err)
+		user, _, err = httpdtest.GetUserByUsername(user.Username, http.StatusOK)
+		assert.NoError(t, err)
+		assert.Equal(t, 2, user.UsedQuotaFiles)
+		assert.Equal(t, expectedSize+encryptedSize, user.UsedQuotaSize)
+		// try to overwrite this file with a big one, this cause an overquota error
+		// the partial file is deleted and the quota updated
+		_, err = reader.Seek(0, io.SeekStart)
+		assert.NoError(t, err)
+		f, err = client.Create(testFileName)
+		assert.NoError(t, err)
+		_, err = io.Copy(f, reader)
+		assert.Error(t, err)
+		err = f.Close()
+		assert.Error(t, err)
+		user, _, err = httpdtest.GetUserByUsername(user.Username, http.StatusOK)
+		assert.NoError(t, err)
+		assert.Equal(t, 1, user.UsedQuotaFiles)
+		assert.Equal(t, expectedSize, user.UsedQuotaSize)
+	}
+
+	_, err = httpdtest.RemoveUser(user, http.StatusOK)
+	assert.NoError(t, err)
+	err = os.RemoveAll(user.GetHomeDir())
+	assert.NoError(t, err)
+}
+
 func TestChtimesOpenHandle(t *testing.T) {
 	localUser, _, err := httpdtest.AddUser(getTestUser(), http.StatusCreated)
 	assert.NoError(t, err)

internal/common/transfer.go

@@ -306,19 +306,26 @@ func (t *BaseTransfer) TransferError(err error) {
 		t.BytesReceived.Load(), elapsed)
 }
 
-func (t *BaseTransfer) getUploadFileSize() (int64, error) {
+func (t *BaseTransfer) getUploadFileSize() (int64, int, error) {
 	var fileSize int64
+	var deletedFiles int
+
 	info, err := t.Fs.Stat(t.fsPath)
 	if err == nil {
 		fileSize = info.Size()
 	}
-	if vfs.IsCryptOsFs(t.Fs) && t.ErrTransfer != nil {
+	if t.ErrTransfer != nil && vfs.IsCryptOsFs(t.Fs) {
 		errDelete := t.Fs.Remove(t.fsPath, false)
 		if errDelete != nil {
 			t.Connection.Log(logger.LevelWarn, "error removing partial crypto file %#v: %v", t.fsPath, errDelete)
+		} else {
+			fileSize = 0
+			deletedFiles = 1
+			t.BytesReceived.Store(0)
+			t.MinWriteOffset = 0
 		}
 	}
-	return fileSize, err
+	return fileSize, deletedFiles, err
 }
 
 // return 1 if the file is outside the user home dir
@@ -347,10 +354,7 @@ func (t *BaseTransfer) Close() error {
 	defer t.Connection.RemoveTransfer(t)
 
 	var err error
-	numFiles := 0
+	numFiles := t.getUploadedFiles()
-	if t.isNewFile {
-		numFiles = 1
-	}
 	metric.TransferCompleted(t.BytesSent.Load(), t.BytesReceived.Load(),
 		t.transferType, t.ErrTransfer, vfs.IsSFTPFs(t.Fs))
 	if t.transferQuota.HasSizeLimits() {
@@ -361,7 +365,6 @@ func (t *BaseTransfer) Close() error {
 		// if quota is exceeded we try to remove the partial file for uploads to local filesystem
 		err = t.Fs.Remove(t.File.Name(), false)
 		if err == nil {
-			numFiles--
 			t.BytesReceived.Store(0)
 			t.MinWriteOffset = 0
 		}
@@ -373,13 +376,12 @@ func (t *BaseTransfer) Close() error {
 			t.Connection.Log(logger.LevelDebug, "atomic upload completed, rename: %#v -> %#v, error: %v",
 				t.effectiveFsPath, t.fsPath, err)
 			// the file must be removed if it is uploaded to a path outside the home dir and cannot be renamed
-			numFiles -= t.checkUploadOutsideHomeDir(err)
+			t.checkUploadOutsideHomeDir(err)
 		} else {
 			err = t.Fs.Remove(t.effectiveFsPath, false)
 			t.Connection.Log(logger.LevelWarn, "atomic upload completed with error: \"%v\", delete temporary file: %#v, deletion error: %v",
 				t.ErrTransfer, t.effectiveFsPath, err)
 			if err == nil {
-				numFiles--
 				t.BytesReceived.Store(0)
 				t.MinWriteOffset = 0
 			}
@@ -393,11 +395,19 @@ func (t *BaseTransfer) Close() error {
 		ExecuteActionNotification(t.Connection, operationDownload, t.fsPath, t.requestPath, "", "", "", //nolint:errcheck
 			t.BytesSent.Load(), t.ErrTransfer)
 	} else {
-		uploadFileSize = t.BytesReceived.Load() + t.MinWriteOffset
+		statSize, deletedFiles, errStat := t.getUploadFileSize()
-		if statSize, errStat := t.getUploadFileSize(); errStat == nil {
+		if errStat == nil {
 			uploadFileSize = statSize
+		} else {
+			uploadFileSize = t.BytesReceived.Load() + t.MinWriteOffset
+			if t.Fs.IsNotExist(errStat) {
+				uploadFileSize = 0
+				numFiles--
+			}
 		}
-		t.Connection.Log(logger.LevelDebug, "upload file size %v", uploadFileSize)
+		numFiles -= deletedFiles
+		t.Connection.Log(logger.LevelDebug, "upload file size %d, num files %d, deleted files %d, fs path %q",
+			uploadFileSize, numFiles, deletedFiles, t.fsPath)
 		numFiles, uploadFileSize = t.executeUploadHook(numFiles, uploadFileSize)
 		t.updateQuota(numFiles, uploadFileSize)
 		t.updateTimes()
@@ -458,6 +468,14 @@ func (t *BaseTransfer) executeUploadHook(numFiles int, fileSize int64) (int, int
 	return numFiles, fileSize
 }
 
+func (t *BaseTransfer) getUploadedFiles() int {
+	numFiles := 0
+	if t.isNewFile {
+		numFiles = 1
+	}
+	return numFiles
+}
+
 func (t *BaseTransfer) updateTimes() {
 	if !t.aTime.IsZero() && !t.mTime.IsZero() {
 		err := t.Fs.Chtimes(t.fsPath, t.aTime, t.mTime, true)
@@ -467,12 +485,12 @@ func (t *BaseTransfer) updateTimes() {
 }
 
 func (t *BaseTransfer) updateQuota(numFiles int, fileSize int64) bool {
-	// S3 uploads are atomic, if there is an error nothing is uploaded
+	// Uploads on some filesystem (S3 and similar) are atomic, if there is an error nothing is uploaded
-	if t.File == nil && t.ErrTransfer != nil && !t.Connection.User.HasBufferedSFTP(t.GetVirtualPath()) {
+	if t.File == nil && t.ErrTransfer != nil && vfs.HasImplicitAtomicUploads(t.Fs) {
 		return false
 	}
 	sizeDiff := fileSize - t.InitialSize
-	if t.transferType == TransferUpload && (numFiles != 0 || sizeDiff > 0) {
+	if t.transferType == TransferUpload && (numFiles != 0 || sizeDiff != 0) {
 		vfolder, err := t.Connection.User.GetVirtualFolderForPath(path.Dir(t.requestPath))
 		if err == nil {
 			dataprovider.UpdateVirtualFolderQuota(&vfolder.BaseVirtualFolder, numFiles, //nolint:errcheck

internal/common/transfer_test.go

@@ -40,7 +40,6 @@ func TestTransferUpdateQuota(t *testing.T) {
 	transfer.BytesReceived.Store(123)
 	errFake := errors.New("fake error")
 	transfer.TransferError(errFake)
-	assert.False(t, transfer.updateQuota(1, 0))
 	err := transfer.Close()
 	if assert.Error(t, err) {
 		assert.EqualError(t, err, errFake.Error())
@@ -61,6 +60,10 @@ func TestTransferUpdateQuota(t *testing.T) {
 	assert.True(t, transfer.updateQuota(1, 0))
 	err = transfer.Close()
 	assert.NoError(t, err)
+
+	transfer.ErrTransfer = errFake
+	transfer.Fs = newMockOsFs(true, "", "", "S3Fs fake")
+	assert.False(t, transfer.updateQuota(1, 0))
 }
 
 func TestTransferThrottling(t *testing.T) {
@@ -297,13 +300,14 @@ func TestRemovePartialCryptoFile(t *testing.T) {
 	transfer := NewBaseTransfer(nil, conn, nil, testFile, testFile, "/transfer_test_file", TransferUpload,
 		0, 0, 0, 0, true, fs, dataprovider.TransferQuota{})
 	transfer.ErrTransfer = errors.New("test error")
-	_, err = transfer.getUploadFileSize()
+	_, _, err = transfer.getUploadFileSize()
 	assert.Error(t, err)
 	err = os.WriteFile(testFile, []byte("test data"), os.ModePerm)
 	assert.NoError(t, err)
-	size, err := transfer.getUploadFileSize()
+	size, deletedFiles, err := transfer.getUploadFileSize()
 	assert.NoError(t, err)
-	assert.Equal(t, int64(9), size)
+	assert.Equal(t, int64(0), size)
+	assert.Equal(t, 1, deletedFiles)
 	assert.NoFileExists(t, testFile)
 }
 

internal/dataprovider/user.go

@@ -496,15 +496,6 @@ func (u *User) GetPermissionsForPath(p string) []string {
 	return permissions
 }
 
-// HasBufferedSFTP returns true if the user has a SFTP filesystem with buffering enabled
-func (u *User) HasBufferedSFTP(name string) bool {
-	fs := u.GetFsConfigForPath(name)
-	if fs.Provider == sdk.SFTPFilesystemProvider {
-		return fs.SFTPConfig.BufferSize > 0
-	}
-	return false
-}
-
 func (u *User) getForbiddenSFTPSelfUsers(username string) ([]string, error) {
 	sftpUser, err := UserExists(username)
 	if err == nil {

internal/vfs/azblobfs.go

@@ -54,6 +54,7 @@ import (
 
 const (
 	azureDefaultEndpoint = "blob.core.windows.net"
+	azBlobFsName         = "AzureBlobFs"
 )
 
 // AzureBlobFs is a Fs implementation for Azure Blob storage.
@@ -158,9 +159,9 @@ func (fs *AzureBlobFs) initFromSASURL() (Fs, error) {
 // Name returns the name for the Fs implementation
 func (fs *AzureBlobFs) Name() string {
 	if !fs.config.SASURL.IsEmpty() {
-		return fmt.Sprintf("Azure Blob with SAS URL, container %#v", fs.config.Container)
+		return fmt.Sprintf("%s with SAS URL, container %q", azBlobFsName, fs.config.Container)
 	}
-	return fmt.Sprintf("Azure Blob container %#v", fs.config.Container)
+	return fmt.Sprintf("%s container %q", azBlobFsName, fs.config.Container)
 }
 
 // ConnectionID returns the connection ID associated to this Fs implementation

internal/vfs/gcsfs.go

@@ -45,6 +45,7 @@ import (
 
 const (
 	defaultGCSPageSize = 5000
+	gcsfsName          = "GCSFs"
 )
 
 var (
@@ -104,7 +105,7 @@ func NewGCSFs(connectionID, localTempDir, mountPath string, config GCSFsConfig)
 
 // Name returns the name for the Fs implementation
 func (fs *GCSFs) Name() string {
-	return fmt.Sprintf("GCSFs bucket %#v", fs.config.Bucket)
+	return fmt.Sprintf("%s bucket %q", gcsfsName, fs.config.Bucket)
 }
 
 // ConnectionID returns the connection ID associated to this Fs implementation

internal/vfs/s3fs.go

@@ -57,6 +57,7 @@ const (
 	// using this mime type for directories improves compatibility with s3fs-fuse
 	s3DirMimeType        = "application/x-directory"
 	s3TransferBufferSize = 256 * 1024
+	s3fsName             = "S3Fs"
 )
 
 // S3Fs is a Fs implementation for AWS S3 compatible object storages
@@ -139,7 +140,7 @@ func NewS3Fs(connectionID, localTempDir, mountPath string, s3Config S3FsConfig)
 
 // Name returns the name for the Fs implementation
 func (fs *S3Fs) Name() string {
-	return fmt.Sprintf("S3Fs bucket %#v", fs.config.Bucket)
+	return fmt.Sprintf("%s bucket %q", s3fsName, fs.config.Bucket)
 }
 
 // ConnectionID returns the connection ID associated to this Fs implementation

internal/vfs/vfs.go

@@ -746,6 +746,20 @@ func HasTruncateSupport(fs Fs) bool {
 	return IsLocalOsFs(fs) || IsSFTPFs(fs) || IsHTTPFs(fs)
 }
 
+// HasImplicitAtomicUploads returns true if the fs don't persists partial files on error
+func HasImplicitAtomicUploads(fs Fs) bool {
+	if strings.HasPrefix(fs.Name(), s3fsName) {
+		return true
+	}
+	if strings.HasPrefix(fs.Name(), gcsfsName) {
+		return true
+	}
+	if strings.HasPrefix(fs.Name(), azBlobFsName) {
+		return true
+	}
+	return false
+}
+
 // HasOpenRWSupport returns true if the fs can open a file
 // for reading and writing at the same time
 func HasOpenRWSupport(fs Fs) bool {