lib/fs: substitute ReadFullData with MustReadData

Callers of ReadFullData() log the error and then exit.
So let's log the error with the path to the filename and the call stack
inside MustReadData(). This simplifies the code at callers' side,
while leaving the debuggability at the same level.

lib/fs/fs.go

@@ -337,19 +337,18 @@ func MustCopyFile(srcPath, dstPath string) {
 	MustSyncPath(dstPath)
 }
 
-// ReadFullData reads len(data) bytes from r.
-func ReadFullData(r io.Reader, data []byte) error {
+// MustReadData reads len(data) bytes from r.
+func MustReadData(r filestream.ReadCloser, data []byte) {
 	n, err := io.ReadFull(r, data)
 	if err != nil {
 		if err == io.EOF {
-			return io.EOF
+			return
 		}
-		return fmt.Errorf("cannot read %d bytes; read only %d bytes; error: %w", len(data), n, err)
+		logger.Panicf("FATAL: cannot read %d bytes from %s; read only %d bytes; error: %s", len(data), r.Path(), n, err)
 	}
 	if n != len(data) {
-		logger.Panicf("BUG: io.ReadFull read only %d bytes; must read %d bytes", n, len(data))
+		logger.Panicf("BUG: io.ReadFull read only %d bytes from %s; must read %d bytes", n, r.Path(), len(data))
 	}
-	return nil
 }
 
 // MustWriteData writes data to w.

lib/mergeset/block_stream_reader.go

@@ -234,16 +234,10 @@ func (bsr *blockStreamReader) Next() bool {
 	bsr.bhIdx++
 
 	bsr.sb.itemsData = bytesutil.ResizeNoCopyMayOverallocate(bsr.sb.itemsData, int(bsr.bh.itemsBlockSize))
-	if err := fs.ReadFullData(bsr.itemsReader, bsr.sb.itemsData); err != nil {
-		bsr.err = fmt.Errorf("cannot read compressed items block with size %d: %w", bsr.bh.itemsBlockSize, err)
-		return false
-	}
+	fs.MustReadData(bsr.itemsReader, bsr.sb.itemsData)
 
 	bsr.sb.lensData = bytesutil.ResizeNoCopyMayOverallocate(bsr.sb.lensData, int(bsr.bh.lensBlockSize))
-	if err := fs.ReadFullData(bsr.lensReader, bsr.sb.lensData); err != nil {
-		bsr.err = fmt.Errorf("cannot read compressed lens block with size %d: %w", bsr.bh.lensBlockSize, err)
-		return false
-	}
+	fs.MustReadData(bsr.lensReader, bsr.sb.lensData)
 
 	if err := bsr.Block.UnmarshalData(&bsr.sb, bsr.bh.firstItem, bsr.bh.commonPrefix, bsr.bh.itemsCount, bsr.bh.marshalType); err != nil {
 		bsr.err = fmt.Errorf("cannot unmarshal inmemoryBlock from storageBlock with firstItem=%X, commonPrefix=%X, itemsCount=%d, marshalType=%d: %w",
@@ -283,9 +277,7 @@ func (bsr *blockStreamReader) readNextBHS() error {
 
 	// Read compressed index block.
 	bsr.packedBuf = bytesutil.ResizeNoCopyMayOverallocate(bsr.packedBuf, int(mr.indexBlockSize))
-	if err := fs.ReadFullData(bsr.indexReader, bsr.packedBuf); err != nil {
-		return fmt.Errorf("cannot read compressed index block with size %d: %w", mr.indexBlockSize, err)
-	}
+	fs.MustReadData(bsr.indexReader, bsr.packedBuf)
 
 	// Unpack the compressed index block.
 	var err error

lib/storage/block_stream_reader.go

@@ -30,13 +30,9 @@ type blockStreamReader struct {
 
 	ph partHeader
 
-	// Use io.Reader type for timestampsReader and valuesReader
-	// in order to remove I2I conversion in readBlock
-	// when passing them to fs.ReadFullData
-	timestampsReader io.Reader
-	valuesReader     io.Reader
-
-	indexReader filestream.ReadCloser
+	timestampsReader filestream.ReadCloser
+	valuesReader     filestream.ReadCloser
+	indexReader      filestream.ReadCloser
 
 	mrs []metaindexRow
 
@@ -68,11 +64,6 @@ type blockStreamReader struct {
 	err error
 }
 
-func (bsr *blockStreamReader) assertWriteClosers() {
-	_ = bsr.timestampsReader.(filestream.ReadCloser)
-	_ = bsr.valuesReader.(filestream.ReadCloser)
-}
-
 func (bsr *blockStreamReader) reset() {
 	bsr.Block.Reset()
 
@@ -128,8 +119,6 @@ func (bsr *blockStreamReader) InitFromInmemoryPart(mp *inmemoryPart) {
 	if err != nil {
 		logger.Panicf("BUG: cannot unmarshal metaindex rows from inmemoryPart: %s", err)
 	}
-
-	bsr.assertWriteClosers()
 }
 
 // InitFromFilePart initializes bsr from a file-based part on the given path.
@@ -189,8 +178,6 @@ func (bsr *blockStreamReader) InitFromFilePart(path string) error {
 	bsr.indexReader = indexFile
 	bsr.mrs = mrs
 
-	bsr.assertWriteClosers()
-
 	return nil
 }
 
@@ -198,8 +185,8 @@ func (bsr *blockStreamReader) InitFromFilePart(path string) error {
 //
 // It closes *Reader files passed to Init.
 func (bsr *blockStreamReader) MustClose() {
-	bsr.timestampsReader.(filestream.ReadCloser).MustClose()
-	bsr.valuesReader.(filestream.ReadCloser).MustClose()
+	bsr.timestampsReader.MustClose()
+	bsr.valuesReader.MustClose()
 	bsr.indexReader.MustClose()
 
 	bsr.reset()
@@ -309,18 +296,14 @@ func (bsr *blockStreamReader) readBlock() error {
 		bsr.Block.timestampsData = append(bsr.Block.timestampsData[:0], bsr.prevTimestampsData...)
 	} else {
 		bsr.Block.timestampsData = bytesutil.ResizeNoCopyMayOverallocate(bsr.Block.timestampsData, int(bsr.Block.bh.TimestampsBlockSize))
-		if err := fs.ReadFullData(bsr.timestampsReader, bsr.Block.timestampsData); err != nil {
-			return fmt.Errorf("cannot read timestamps block at offset %d: %w", bsr.timestampsBlockOffset, err)
-		}
+		fs.MustReadData(bsr.timestampsReader, bsr.Block.timestampsData)
 		bsr.prevTimestampsBlockOffset = bsr.timestampsBlockOffset
 		bsr.prevTimestampsData = append(bsr.prevTimestampsData[:0], bsr.Block.timestampsData...)
 	}
 
 	// Read values data.
 	bsr.Block.valuesData = bytesutil.ResizeNoCopyMayOverallocate(bsr.Block.valuesData, int(bsr.Block.bh.ValuesBlockSize))
-	if err := fs.ReadFullData(bsr.valuesReader, bsr.Block.valuesData); err != nil {
-		return fmt.Errorf("cannot read values block at offset %d: %w", bsr.valuesBlockOffset, err)
-	}
+	fs.MustReadData(bsr.valuesReader, bsr.Block.valuesData)
 
 	// Update offsets.
 	if !usePrevTimestamps {
@@ -353,9 +336,7 @@ func (bsr *blockStreamReader) readIndexBlock() error {
 
 	// Read index block.
 	bsr.compressedIndexData = bytesutil.ResizeNoCopyMayOverallocate(bsr.compressedIndexData, int(bsr.mr.IndexBlockSize))
-	if err := fs.ReadFullData(bsr.indexReader, bsr.compressedIndexData); err != nil {
-		return fmt.Errorf("cannot read index block at offset %d: %w", bsr.indexBlockOffset, err)
-	}
+	fs.MustReadData(bsr.indexReader, bsr.compressedIndexData)
 	tmpData, err := encoding.DecompressZSTD(bsr.indexData[:0], bsr.compressedIndexData)
 	if err != nil {
 		return fmt.Errorf("cannot decompress index block at offset %d: %w", bsr.indexBlockOffset, err)