lib/backup/common: consistently use canonical path with / directory separators at Part.Path

Previously Part.Path could contain `\` directory separators on Windows OS,
which could result in incorrect filepaths generation when making backups at object storage.

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4704

This is a follow-up for f2df8ad480

lib/backup/common/part.go

@@ -2,6 +2,7 @@ package common
 
 import (
 	"fmt"
+	"path/filepath"
 	"regexp"
 	"sort"
 	"strconv"
@@ -15,6 +16,9 @@ import (
 // Each source file can be split into parts with up to MaxPartSize sizes.
 type Part struct {
 	// Path is the path to file for backup.
+	//
+	// Path must consistently use `/` as directory separator.
+	// Use ToCanonicalPath() function for converting local directory separators to `/`.
 	Path string
 
 	// FileSize is the size of the whole file for the given part.
@@ -51,11 +55,30 @@ func (p *Part) RemotePath(prefix string) string {
 	return fmt.Sprintf("%s/%s/%016X_%016X_%016X", prefix, p.Path, p.FileSize, p.Offset, p.Size)
 }
 
+// LocalPath returns local path for p at the given dir.
+func (p *Part) LocalPath(dir string) string {
+	path := p.Path
+	if filepath.Separator != '/' {
+		path = strings.ReplaceAll(path, "/", string(filepath.Separator))
+	}
+	return filepath.Join(dir, path)
+}
+
+// ToCanonicalPath returns canonical path by replacing local directory separators with `/`.
+func ToCanonicalPath(path string) string {
+	if filepath.Separator == '/' {
+		return path
+	}
+	return strings.ReplaceAll(path, string(filepath.Separator), "/")
+}
+
 var partNameRegexp = regexp.MustCompile(`^(.+)[/\\]([0-9A-F]{16})_([0-9A-F]{16})_([0-9A-F]{16})$`)
 
 // ParseFromRemotePath parses p from remotePath.
 //
 // Returns true on success.
+//
+// remotePath must be in canonical form received from ToCanonicalPath().
 func (p *Part) ParseFromRemotePath(remotePath string) bool {
 	tmp := partNameRegexp.FindStringSubmatch(remotePath)
 	if len(tmp) != 5 {

lib/backup/fscommon/fscommon.go

@@ -10,9 +10,10 @@ import (
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 )
 
-// AppendFiles appends all the files from dir to dst.
+// AppendFiles appends paths to all the files from local dir to dst.
 //
-// All the appended files will have dir prefix.
+// All the appended filepaths will have dir prefix.
+// The returned paths have local OS-specific directory separators.
 func AppendFiles(dst []string, dir string) ([]string, error) {
 	d, err := os.Open(dir)
 	if err != nil {

lib/backup/fslocal/fslocal.go

@@ -77,7 +77,7 @@ func (fs *FS) ListParts() ([]common.Part, error) {
 		if err != nil {
 			return nil, fmt.Errorf("cannot stat %q: %w", file, err)
 		}
-		path := file[len(dir):]
+		path := common.ToCanonicalPath(file[len(dir):])
 		size := uint64(fi.Size())
 		if size == 0 {
 			parts = append(parts, common.Part{
@@ -146,8 +146,9 @@ func (fs *FS) NewWriteCloser(p common.Part) (io.WriteCloser, error) {
 	return blwc, nil
 }
 
-// DeletePath deletes the given path from fs and returns the size
-// for the deleted file.
+// DeletePath deletes the given path from fs and returns the size for the deleted file.
+//
+// The path must be in canonical form, e.g. it must have `/` directory separators
 func (fs *FS) DeletePath(path string) (uint64, error) {
 	p := common.Part{
 		Path: path,
@@ -187,7 +188,7 @@ func (fs *FS) mkdirAll(filePath string) error {
 }
 
 func (fs *FS) path(p common.Part) string {
-	return filepath.Join(fs.Dir, p.Path)
+	return p.LocalPath(fs.Dir)
 }
 
 type limitedReadCloser struct {

lib/backup/fsremote/fsremote.go

@@ -58,7 +58,8 @@ func (fs *FS) ListParts() ([]common.Part, error) {
 			continue
 		}
 		var p common.Part
-		if !p.ParseFromRemotePath(file[len(dir):]) {
+		remotePath := common.ToCanonicalPath(file[len(dir):])
+		if !p.ParseFromRemotePath(remotePath) {
 			logger.Infof("skipping unknown file %s", file)
 			continue
 		}
@@ -68,7 +69,6 @@ func (fs *FS) ListParts() ([]common.Part, error) {
 			return nil, fmt.Errorf("cannot stat file %q for part %q: %w", file, p.Path, err)
 		}
 		p.ActualSize = uint64(fi.Size())
-		p.Path = pathToCanonical(p.Path)
 		parts = append(parts, p)
 	}
 	return parts, nil
@@ -76,7 +76,6 @@ func (fs *FS) ListParts() ([]common.Part, error) {
 
 // DeletePart deletes the given part p from fs.
 func (fs *FS) DeletePart(p common.Part) error {
-	p.Path = canonicalPathToLocal(p.Path)
 	path := fs.path(p)
 	if err := os.Remove(path); err != nil {
 		return fmt.Errorf("cannot remove %q: %w", path, err)
@@ -97,7 +96,6 @@ func (fs *FS) CopyPart(srcFS common.OriginFS, p common.Part) error {
 	if !ok {
 		return fmt.Errorf("cannot perform server-side copying from %s to %s: both of them must be fsremote", srcFS, fs)
 	}
-	p.Path = canonicalPathToLocal(p.Path)
 	srcPath := src.path(p)
 	dstPath := fs.path(p)
 	if err := fs.mkdirAll(dstPath); err != nil {
@@ -142,7 +140,6 @@ func (fs *FS) CopyPart(srcFS common.OriginFS, p common.Part) error {
 
 // DownloadPart download part p from fs to w.
 func (fs *FS) DownloadPart(p common.Part, w io.Writer) error {
-	p.Path = canonicalPathToLocal(p.Path)
 	path := fs.path(p)
 	r, err := os.Open(path)
 	if err != nil {
@@ -198,14 +195,13 @@ func (fs *FS) mkdirAll(filePath string) error {
 }
 
 func (fs *FS) path(p common.Part) string {
-	return filepath.Join(fs.Dir, p.Path, fmt.Sprintf("%016X_%016X_%016X", p.FileSize, p.Offset, p.Size))
+	return filepath.Join(p.LocalPath(fs.Dir), fmt.Sprintf("%016X_%016X_%016X", p.FileSize, p.Offset, p.Size))
 }
 
 // DeleteFile deletes filePath at fs.
 //
 // The function does nothing if the filePath doesn't exist.
 func (fs *FS) DeleteFile(filePath string) error {
-	filePath = canonicalPathToLocal(filePath)
 	path := filepath.Join(fs.Dir, filePath)
 	err := os.Remove(path)
 	if err != nil && !os.IsNotExist(err) {
@@ -247,6 +243,5 @@ func (fs *FS) HasFile(filePath string) (bool, error) {
 // ReadFile returns the content of filePath at fs.
 func (fs *FS) ReadFile(filePath string) ([]byte, error) {
 	path := filepath.Join(fs.Dir, filePath)
-
 	return os.ReadFile(path)
 }

lib/backup/fsremote/normilize_path_bsd.go

@@ -1,12 +0,0 @@
-//go:build freebsd || openbsd || dragonfly || netbsd
-// +build freebsd openbsd dragonfly netbsd
-
-package fsremote
-
-func pathToCanonical(path string) string {
-	return path
-}
-
-func canonicalPathToLocal(path string) string {
-	return path
-}

lib/backup/fsremote/normilize_path_darwin.go

@@ -1,9 +0,0 @@
-package fsremote
-
-func pathToCanonical(path string) string {
-	return path
-}
-
-func canonicalPathToLocal(path string) string {
-	return path
-}

lib/backup/fsremote/normilize_path_linux.go

@@ -1,9 +0,0 @@
-package fsremote
-
-func pathToCanonical(path string) string {
-	return path
-}
-
-func canonicalPathToLocal(path string) string {
-	return path
-}

lib/backup/fsremote/normilize_path_solaris.go

@@ -1,9 +0,0 @@
-package fsremote
-
-func pathToCanonical(path string) string {
-	return path
-}
-
-func canonicalPathToLocal(path string) string {
-	return path
-}

lib/backup/fsremote/normilize_path_windows.go

@@ -1,11 +0,0 @@
-package fsremote
-
-import "strings"
-
-func pathToCanonical(path string) string {
-	return strings.ReplaceAll(path, "\\", "/")
-}
-
-func canonicalPathToLocal(path string) string {
-	return strings.ReplaceAll(path, "/", "\\")
-}