fix: fork os.MkdirAll to optimize cases where parent exists (#15379)

a/b/c/d/ where `a/b/c/` exists results in additional syscalls
such as an Lstat() call to verify if the `a/b/c/` exists
and its a directory.

We do not need to do this on MinIO since the parent prefixes
if exist, we can simply return success without spending
additional syscalls.

Also this implementation attempts to simply use Access() calls
to avoid os.Stat() calls since the latter does memory allocation
for things we do not need to use.

Access() is simpler since we have a predictable structure on
the backend and we know exactly how our path structures are.

cmd/fs-v1-rwpool.go

@@ -187,6 +187,8 @@ func (fsi *fsIOPool) Create(path string) (wlk *lock.LockedFile, err error) {
 			return nil, errFileAccessDenied
 		case isSysErrIsDir(err):
 			return nil, errIsNotRegular
+		case isSysErrNotDir(err):
+			return nil, errFileAccessDenied
 		case isSysErrPathNotFound(err):
 			return nil, errFileAccessDenied
 		default:

cmd/os-instrumented.go

@@ -35,6 +35,7 @@ type osMetric uint8
 const (
 	osMetricRemoveAll osMetric = iota
 	osMetricMkdirAll
+	osMetricMkdir
 	osMetricRename
 	osMetricOpenFile
 	osMetricOpen
@@ -114,10 +115,16 @@ func RemoveAll(dirPath string) error {
 	return os.RemoveAll(dirPath)
 }
 
+// Mkdir captures time taken to call os.Mkdir
+func Mkdir(dirPath string, mode os.FileMode) error {
+	defer updateOSMetrics(osMetricMkdir, dirPath)()
+	return os.Mkdir(dirPath, mode)
+}
+
 // MkdirAll captures time taken to call os.MkdirAll
 func MkdirAll(dirPath string, mode os.FileMode) error {
 	defer updateOSMetrics(osMetricMkdirAll, dirPath)()
-	return os.MkdirAll(dirPath, mode)
+	return osMkdirAll(dirPath, mode)
 }
 
 // Rename captures time taken to call os.Rename

cmd/os-reliable.go

@@ -104,7 +104,7 @@ func reliableMkdirAll(dirPath string, mode os.FileMode) (err error) {
 	i := 0
 	for {
 		// Creates all the parent directories, with mode 0777 mkdir honors system umask.
-		if err = MkdirAll(dirPath, mode); err != nil {
+		if err = osMkdirAll(dirPath, mode); err != nil {
 			// Retry only for the first retryable error.
 			if osIsNotExist(err) && i == 0 {
 				i++
@@ -166,6 +166,7 @@ func reliableRename(srcFilePath, dstFilePath string) (err error) {
 	if err = reliableMkdirAll(path.Dir(dstFilePath), 0o777); err != nil {
 		return err
 	}
+
 	i := 0
 	for {
 		// After a successful parent directory create attempt a renameAll.

cmd/os_other.go

@@ -31,6 +31,10 @@ func access(name string) error {
 	return err
 }
 
+func osMkdirAll(dirPath string, perm os.FileMode) error {
+	return os.MkdirAll(dirPath, perm)
+}
+
 // readDirFn applies the fn() function on each entries at dirPath, doesn't recurse into
 // the directory itself, if the dirPath doesn't exist this function doesn't return
 // an error.

cmd/os_unix.go

@@ -38,6 +38,55 @@ func access(name string) error {
 	return nil
 }
 
+// Forked from Golang but chooses fast path upon os.Mkdir()
+// error to avoid os.Lstat() call.
+//
+// osMkdirAll creates a directory named path,
+// along with any necessary parents, and returns nil,
+// or else returns an error.
+// The permission bits perm (before umask) are used for all
+// directories that MkdirAll creates.
+// If path is already a directory, MkdirAll does nothing
+// and returns nil.
+func osMkdirAll(dirPath string, perm os.FileMode) error {
+	// Fast path: if we can tell whether path is a directory or file, stop with success or error.
+	err := Access(dirPath)
+	if err == nil {
+		return nil
+	}
+	if !osIsNotExist(err) {
+		return &os.PathError{Op: "mkdir", Path: dirPath, Err: err}
+	}
+
+	// Slow path: make sure parent exists and then call Mkdir for path.
+	i := len(dirPath)
+	for i > 0 && os.IsPathSeparator(dirPath[i-1]) { // Skip trailing path separator.
+		i--
+	}
+
+	j := i
+	for j > 0 && !os.IsPathSeparator(dirPath[j-1]) { // Scan backward over element.
+		j--
+	}
+
+	if j > 1 {
+		// Create parent.
+		if err = osMkdirAll(dirPath[:j-1], perm); err != nil {
+			return err
+		}
+	}
+
+	// Parent now exists; invoke Mkdir and use its result.
+	if err = Mkdir(dirPath, perm); err != nil {
+		if osIsExist(err) {
+			return nil
+		}
+		return err
+	}
+
+	return nil
+}
+
 // The buffer must be at least a block long.
 // refer https://github.com/golang/go/issues/24015
 const blockSize = 8 << 10 // 8192

cmd/os_windows.go

@@ -31,6 +31,10 @@ func access(name string) error {
 	return err
 }
 
+func osMkdirAll(dirPath string, perm os.FileMode) error {
+	return os.MkdirAll(dirPath, perm)
+}
+
 // readDirFn applies the fn() function on each entries at dirPath, doesn't recurse into
 // the directory itself, if the dirPath doesn't exist this function doesn't return
 // an error.

cmd/osmetric_string.go

@@ -10,24 +10,25 @@ func _() {
 	var x [1]struct{}
 	_ = x[osMetricRemoveAll-0]
 	_ = x[osMetricMkdirAll-1]
-	_ = x[osMetricRename-2]
-	_ = x[osMetricOpenFile-3]
-	_ = x[osMetricOpen-4]
-	_ = x[osMetricOpenFileDirectIO-5]
-	_ = x[osMetricLstat-6]
-	_ = x[osMetricRemove-7]
-	_ = x[osMetricStat-8]
-	_ = x[osMetricAccess-9]
-	_ = x[osMetricCreate-10]
-	_ = x[osMetricReadDirent-11]
-	_ = x[osMetricFdatasync-12]
-	_ = x[osMetricSync-13]
-	_ = x[osMetricLast-14]
+	_ = x[osMetricMkdir-2]
+	_ = x[osMetricRename-3]
+	_ = x[osMetricOpenFile-4]
+	_ = x[osMetricOpen-5]
+	_ = x[osMetricOpenFileDirectIO-6]
+	_ = x[osMetricLstat-7]
+	_ = x[osMetricRemove-8]
+	_ = x[osMetricStat-9]
+	_ = x[osMetricAccess-10]
+	_ = x[osMetricCreate-11]
+	_ = x[osMetricReadDirent-12]
+	_ = x[osMetricFdatasync-13]
+	_ = x[osMetricSync-14]
+	_ = x[osMetricLast-15]
 }
 
-const _osMetric_name = "RemoveAllMkdirAllRenameOpenFileOpenOpenFileDirectIOLstatRemoveStatAccessCreateReadDirentFdatasyncSyncLast"
+const _osMetric_name = "RemoveAllMkdirAllMkdirRenameOpenFileOpenOpenFileDirectIOLstatRemoveStatAccessCreateReadDirentFdatasyncSyncLast"
 
-var _osMetric_index = [...]uint8{0, 9, 17, 23, 31, 35, 51, 56, 62, 66, 72, 78, 88, 97, 101, 105}
+var _osMetric_index = [...]uint8{0, 9, 17, 22, 28, 36, 40, 56, 61, 67, 71, 77, 83, 93, 102, 106, 110}
 
 func (i osMetric) String() string {
 	if i >= osMetric(len(_osMetric_index)-1) {

cmd/xl-storage.go

@@ -1647,6 +1647,8 @@ func (s *xlStorage) openFileSync(filePath string, mode int) (f *os.File, err err
 			return nil, errIsNotRegular
 		case osIsPermission(err):
 			return nil, errFileAccessDenied
+		case isSysErrNotDir(err):
+			return nil, errFileAccessDenied
 		case isSysErrIO(err):
 			return nil, errFaultyDisk
 		case isSysErrTooManyFiles(err):
@@ -2487,8 +2489,10 @@ func (s *xlStorage) RenameFile(ctx context.Context, srcVolume, srcPath, dstVolum
 				return errFileAccessDenied
 			}
 			if err = Remove(dstFilePath); err != nil {
-				if isSysErrNotEmpty(err) {
+				if isSysErrNotEmpty(err) || isSysErrNotDir(err) {
 					return errFileAccessDenied
+				} else if isSysErrIO(err) {
+					return errFaultyDisk
 				}
 				return err
 			}
@@ -2496,6 +2500,9 @@ func (s *xlStorage) RenameFile(ctx context.Context, srcVolume, srcPath, dstVolum
 	}
 
 	if err = renameAll(srcFilePath, dstFilePath); err != nil {
+		if isSysErrNotEmpty(err) || isSysErrNotDir(err) {
+			return errFileAccessDenied
+		}
 		return osErrToFileErr(err)
 	}