restore: factor out file creation helper

internal/restorer/fileswriter.go

@@ -39,6 +39,48 @@ func newFilesWriter(count int) *filesWriter {
 	}
 }
 
+func createFile(path string, createSize int64, sparse bool) (*os.File, error) {
+	var f *os.File
+	var err error
+	if f, err = os.OpenFile(path, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0600); err != nil {
+		if !fs.IsAccessDenied(err) {
+			return nil, err
+		}
+
+		// If file is readonly, clear the readonly flag by resetting the
+		// permissions of the file and try again
+		// as the metadata will be set again in the second pass and the
+		// readonly flag will be applied again if needed.
+		if err = fs.ResetPermissions(path); err != nil {
+			return nil, err
+		}
+		if f, err = os.OpenFile(path, os.O_TRUNC|os.O_WRONLY, 0600); err != nil {
+			return nil, err
+		}
+	}
+
+	if createSize > 0 {
+		if sparse {
+			err = truncateSparse(f, createSize)
+			if err != nil {
+				_ = f.Close()
+				return nil, err
+			}
+		} else {
+			err := fs.PreallocateFile(f, createSize)
+			if err != nil {
+				// Just log the preallocate error but don't let it cause the restore process to fail.
+				// Preallocate might return an error if the filesystem (implementation) does not
+				// support preallocation or our parameters combination to the preallocate call
+				// This should yield a syscall.ENOTSUP error, but some other errors might also
+				// show up.
+				debug.Log("Failed to preallocate %v with size %v: %v", path, createSize, err)
+			}
+		}
+	}
+	return f, err
+}
+
 func (w *filesWriter) writeToFile(path string, blob []byte, offset int64, createSize int64, sparse bool) error {
 	bucket := &w.buckets[uint(xxhash.Sum64String(path))%uint(len(w.buckets))]
 
@@ -53,22 +95,10 @@ func (w *filesWriter) writeToFile(path string, blob []byte, offset int64, create
 		var f *os.File
 		var err error
 		if createSize >= 0 {
-			if f, err = os.OpenFile(path, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0600); err != nil {
+			f, err = createFile(path, createSize, sparse)
-				if fs.IsAccessDenied(err) {
+			if err != nil {
-					// If file is readonly, clear the readonly flag by resetting the
-					// permissions of the file and try again
-					// as the metadata will be set again in the second pass and the
-					// readonly flag will be applied again if needed.
-					if err = fs.ResetPermissions(path); err != nil {
 				return nil, err
 			}
-					if f, err = os.OpenFile(path, os.O_TRUNC|os.O_WRONLY, 0600); err != nil {
-						return nil, err
-					}
-				} else {
-					return nil, err
-				}
-			}
 		} else if f, err = os.OpenFile(path, os.O_WRONLY, 0600); err != nil {
 			return nil, err
 		}
@@ -76,25 +106,6 @@ func (w *filesWriter) writeToFile(path string, blob []byte, offset int64, create
 		wr := &partialFile{File: f, users: 1, sparse: sparse}
 		bucket.files[path] = wr
 
-		if createSize >= 0 {
-			if sparse {
-				err = truncateSparse(f, createSize)
-				if err != nil {
-					return nil, err
-				}
-			} else {
-				err := fs.PreallocateFile(wr.File, createSize)
-				if err != nil {
-					// Just log the preallocate error but don't let it cause the restore process to fail.
-					// Preallocate might return an error if the filesystem (implementation) does not
-					// support preallocation or our parameters combination to the preallocate call
-					// This should yield a syscall.ENOTSUP error, but some other errors might also
-					// show up.
-					debug.Log("Failed to preallocate %v with size %v: %v", path, createSize, err)
-				}
-			}
-		}
-
 		return wr, nil
 	}