lib/fs: replace fs.OpenReaderAt with fs.MustOpenReaderAt

All the callers for fs.OpenReaderAt expect that the file will be opened.
So it is better to log fatal error inside fs.MustOpenReaderAt instead of leaving this to the caller.

app/vmselect/netstorage/tmp_blocks_file.go

@@ -133,10 +133,7 @@ func (tbf *tmpBlocksFile) Finalize() error {
 		return fmt.Errorf("cannot write the remaining %d bytes to %q: %w", len(tbf.buf), fname, err)
 	}
 	tbf.buf = tbf.buf[:0]
-	r, err := fs.OpenReaderAt(fname)
-	if err != nil {
-		logger.Panicf("FATAL: cannot open %q: %s", fname, err)
-	}
+	r := fs.MustOpenReaderAt(fname)
 	// Hint the OS that the file is read almost sequentiallly.
 	// This should reduce the number of disk seeks, which is important
 	// for HDDs.

lib/fs/reader_at.go

@@ -158,13 +158,13 @@ func (r *ReaderAt) MustFadviseSequentialRead(prefetch bool) {
 	}
 }
 
-// OpenReaderAt opens ReaderAt for reading from filename.
+// MustOpenReaderAt opens ReaderAt for reading from filename.
 //
 // MustClose must be called on the returned ReaderAt when it is no longer needed.
-func OpenReaderAt(path string) (*ReaderAt, error) {
+func MustOpenReaderAt(path string) *ReaderAt {
 	f, err := os.Open(path)
 	if err != nil {
-		return nil, fmt.Errorf("cannot open file %q for reader: %w", path, err)
+		logger.Panicf("FATAL: cannot open file %q for reading: %s", path, err)
 	}
 	var r ReaderAt
 	r.f = f
@@ -172,7 +172,8 @@ func OpenReaderAt(path string) (*ReaderAt, error) {
 	if !*disableMmap {
 		fi, err := f.Stat()
 		if err != nil {
-			return nil, fmt.Errorf("error in stat: %w", err)
+			MustClose(f)
+			logger.Panicf("FATAL: error in fstat(%q): %s", path, err)
 		}
 		size := fi.Size()
 		bm := &pageCacheBitmap{
@@ -188,12 +189,12 @@ func OpenReaderAt(path string) (*ReaderAt, error) {
 		data, err := mmapFile(f, size)
 		if err != nil {
 			MustClose(f)
-			return nil, fmt.Errorf("cannot init reader for %q: %w", path, err)
+			logger.Panicf("FATAL: cannot mmap %q: %s", path, err)
 		}
 		r.mmapData = data
 	}
 	readersCount.Inc()
-	return &r, nil
+	return &r
 }
 
 func pageCacheBitmapCleaner(pcbm *atomic.Value, stopCh <-chan struct{}) {

lib/fs/reader_at_test.go

@@ -22,10 +22,7 @@ func testReaderAt(t *testing.T, bufSize int) {
 		t.Fatalf("cannot create %q: %s", path, err)
 	}
 	defer MustRemoveAll(path)
-	r, err := OpenReaderAt(path)
-	if err != nil {
-		t.Fatalf("error in OpenReaderAt(%q): %s", path, err)
-	}
+	r := MustOpenReaderAt(path)
 	defer r.MustClose()
 
 	buf := make([]byte, bufSize)

lib/fs/reader_at_timing_test.go

@@ -29,10 +29,7 @@ func benchmarkReaderAtMustReadAt(b *testing.B, isMmap bool) {
 		b.Fatalf("cannot create %q: %s", path, err)
 	}
 	defer MustRemoveAll(path)
-	r, err := OpenReaderAt(path)
-	if err != nil {
-		b.Fatalf("error in OpenReaderAt(%q): %s", path, err)
-	}
+	r := MustOpenReaderAt(path)
 	defer r.MustClose()
 
 	b.ResetTimer()

lib/mergeset/part.go

@@ -78,30 +78,15 @@ func openFilePart(path string) (*part, error) {
 	metaindexSize := fs.MustFileSize(metaindexPath)
 
 	indexPath := path + "/index.bin"
-	indexFile, err := fs.OpenReaderAt(indexPath)
-	if err != nil {
-		metaindexFile.MustClose()
-		return nil, fmt.Errorf("cannot open %q: %w", indexPath, err)
-	}
+	indexFile := fs.MustOpenReaderAt(indexPath)
 	indexSize := fs.MustFileSize(indexPath)
 
 	itemsPath := path + "/items.bin"
-	itemsFile, err := fs.OpenReaderAt(itemsPath)
-	if err != nil {
-		metaindexFile.MustClose()
-		indexFile.MustClose()
-		return nil, fmt.Errorf("cannot open %q: %w", itemsPath, err)
-	}
+	itemsFile := fs.MustOpenReaderAt(itemsPath)
 	itemsSize := fs.MustFileSize(itemsPath)
 
 	lensPath := path + "/lens.bin"
-	lensFile, err := fs.OpenReaderAt(lensPath)
-	if err != nil {
-		metaindexFile.MustClose()
-		indexFile.MustClose()
-		itemsFile.MustClose()
-		return nil, fmt.Errorf("cannot open %q: %w", lensPath, err)
-	}
+	lensFile := fs.MustOpenReaderAt(lensPath)
 	lensSize := fs.MustFileSize(lensPath)
 
 	size := metaindexSize + indexSize + itemsSize + lensSize

lib/storage/part.go

@@ -60,27 +60,15 @@ func openFilePart(path string) (*part, error) {
 	}
 
 	timestampsPath := path + "/timestamps.bin"
-	timestampsFile, err := fs.OpenReaderAt(timestampsPath)
-	if err != nil {
-		return nil, fmt.Errorf("cannot open timestamps file: %w", err)
-	}
+	timestampsFile := fs.MustOpenReaderAt(timestampsPath)
 	timestampsSize := fs.MustFileSize(timestampsPath)
 
 	valuesPath := path + "/values.bin"
-	valuesFile, err := fs.OpenReaderAt(valuesPath)
-	if err != nil {
-		timestampsFile.MustClose()
-		return nil, fmt.Errorf("cannot open values file: %w", err)
-	}
+	valuesFile := fs.MustOpenReaderAt(valuesPath)
 	valuesSize := fs.MustFileSize(valuesPath)
 
 	indexPath := path + "/index.bin"
-	indexFile, err := fs.OpenReaderAt(indexPath)
-	if err != nil {
-		timestampsFile.MustClose()
-		valuesFile.MustClose()
-		return nil, fmt.Errorf("cannot open index file: %w", err)
-	}
+	indexFile := fs.MustOpenReaderAt(indexPath)
 	indexSize := fs.MustFileSize(indexPath)
 
 	metaindexPath := path + "/metaindex.bin"