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	in some setups with ordering issues in drive configuration, we should rely on expected parityBlocks instead of `len(disks)/2`
		
			
				
	
	
		
			115 lines
		
	
	
		
			3.1 KiB
		
	
	
	
		
			Go
		
	
	
	
	
	
			
		
		
	
	
			115 lines
		
	
	
		
			3.1 KiB
		
	
	
	
		
			Go
		
	
	
	
	
	
/*
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 * MinIO Cloud Storage, (C) 2016-2020 MinIO, Inc.
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 *
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 * Licensed under the Apache License, Version 2.0 (the "License");
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 * you may not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 *     http://www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an "AS IS" BASIS,
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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package cmd
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import (
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	"bytes"
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	"context"
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	"fmt"
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	"io"
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	"github.com/klauspost/reedsolomon"
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	"github.com/minio/minio/cmd/logger"
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)
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// getDataBlockLen - get length of data blocks from encoded blocks.
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func getDataBlockLen(enBlocks [][]byte, dataBlocks int) int {
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	size := 0
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	// Figure out the data block length.
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	for _, block := range enBlocks[:dataBlocks] {
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		size += len(block)
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	}
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	return size
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}
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// Writes all the data blocks from encoded blocks until requested
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// outSize length. Provides a way to skip bytes until the offset.
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func writeDataBlocks(ctx context.Context, dst io.Writer, enBlocks [][]byte, dataBlocks int, offset int64, length int64) (int64, error) {
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	// Offset and out size cannot be negative.
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	if offset < 0 || length < 0 {
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		logger.LogIf(ctx, errUnexpected)
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		return 0, errUnexpected
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	}
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	// Do we have enough blocks?
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	if len(enBlocks) < dataBlocks {
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		logger.LogIf(ctx, fmt.Errorf("diskBlocks(%d)/dataBlocks(%d) - %w", len(enBlocks), dataBlocks, reedsolomon.ErrTooFewShards))
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		return 0, reedsolomon.ErrTooFewShards
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	}
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	// Do we have enough data?
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	if int64(getDataBlockLen(enBlocks, dataBlocks)) < length {
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		logger.LogIf(ctx, fmt.Errorf("getDataBlockLen(enBlocks, dataBlocks)(%d)/length(%d) - %w", getDataBlockLen(enBlocks, dataBlocks), length, reedsolomon.ErrShortData))
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		return 0, reedsolomon.ErrShortData
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	}
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	// Counter to decrement total left to write.
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	write := length
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	// Counter to increment total written.
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	var totalWritten int64
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	// Write all data blocks to dst.
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	for _, block := range enBlocks[:dataBlocks] {
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		// Skip blocks until we have reached our offset.
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		if offset >= int64(len(block)) {
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			// Decrement offset.
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			offset -= int64(len(block))
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			continue
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		} else {
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			// Skip until offset.
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			block = block[offset:]
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			// Reset the offset for next iteration to read everything
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			// from subsequent blocks.
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			offset = 0
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		}
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		// We have written all the blocks, write the last remaining block.
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		if write < int64(len(block)) {
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			n, err := io.Copy(dst, bytes.NewReader(block[:write]))
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			if err != nil {
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				if err != io.ErrClosedPipe {
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					logger.LogIf(ctx, err)
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				}
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				return 0, err
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			}
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			totalWritten += n
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			break
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		}
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		// Copy the block.
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		n, err := io.Copy(dst, bytes.NewReader(block))
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		if err != nil {
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			// The writer will be closed incase of range queries, which will emit ErrClosedPipe.
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			if err != io.ErrClosedPipe {
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				logger.LogIf(ctx, err)
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			}
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			return 0, err
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		}
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		// Decrement output size.
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		write -= n
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		// Increment written.
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		totalWritten += n
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	}
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	// Success.
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	return totalWritten, nil
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}
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