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Copy patherasure-decode.go
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188 lines (169 loc) · 4.34 KB
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/*
* Minio Cloud Storage, (C) 2016 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cmd
import (
"context"
"io"
"github.com/minio/minio/cmd/logger"
)
// Reads in parallel from bitrotReaders.
type parallelReader struct {
readers []*bitrotReader
dataBlocks int
offset int64
shardSize int64
shardFileSize int64
}
// newParallelReader returns parallelReader.
func newParallelReader(readers []*bitrotReader, dataBlocks int, offset int64, fileSize int64, blocksize int64) *parallelReader {
shardSize := ceilFrac(blocksize, int64(dataBlocks))
shardFileSize := getErasureShardFileSize(blocksize, fileSize, dataBlocks)
return ¶llelReader{
readers,
dataBlocks,
(offset / blocksize) * shardSize,
shardSize,
shardFileSize,
}
}
// Returns if buf can be erasure decoded.
func (p *parallelReader) canDecode(buf [][]byte) bool {
bufCount := 0
for _, b := range buf {
if b != nil {
bufCount++
}
}
return bufCount >= p.dataBlocks
}
// Read reads from bitrotReaders in parallel. Returns p.dataBlocks number of bufs.
func (p *parallelReader) Read() ([][]byte, error) {
type errIdx struct {
idx int
buf []byte
err error
}
errCh := make(chan errIdx)
currReaderIndex := 0
newBuf := make([][]byte, len(p.readers))
if p.offset+p.shardSize > p.shardFileSize {
p.shardSize = p.shardFileSize - p.offset
}
read := func(currReaderIndex int) {
b, err := p.readers[currReaderIndex].ReadChunk(p.offset, p.shardSize)
errCh <- errIdx{currReaderIndex, b, err}
}
readerCount := 0
for _, r := range p.readers {
if r != nil {
readerCount++
}
}
if readerCount < p.dataBlocks {
return nil, errXLReadQuorum
}
readerCount = 0
for i, r := range p.readers {
if r == nil {
continue
}
go read(i)
readerCount++
if readerCount == p.dataBlocks {
currReaderIndex = i + 1
break
}
}
for errVal := range errCh {
if errVal.err == nil {
newBuf[errVal.idx] = errVal.buf
if p.canDecode(newBuf) {
p.offset += int64(p.shardSize)
return newBuf, nil
}
continue
}
p.readers[errVal.idx] = nil
for currReaderIndex < len(p.readers) {
if p.readers[currReaderIndex] != nil {
break
}
currReaderIndex++
}
if currReaderIndex == len(p.readers) {
break
}
go read(currReaderIndex)
currReaderIndex++
}
return nil, errXLReadQuorum
}
// Decode reads from readers, reconstructs data if needed and writes the data to the writer.
func (e Erasure) Decode(ctx context.Context, writer io.Writer, readers []*bitrotReader, offset, length, totalLength int64) error {
if offset < 0 || length < 0 {
logger.LogIf(ctx, errInvalidArgument)
return errInvalidArgument
}
if offset+length > totalLength {
logger.LogIf(ctx, errInvalidArgument)
return errInvalidArgument
}
if length == 0 {
return nil
}
reader := newParallelReader(readers, e.dataBlocks, offset, totalLength, e.blockSize)
startBlock := offset / e.blockSize
endBlock := (offset + length) / e.blockSize
var bytesWritten int64
for block := startBlock; block <= endBlock; block++ {
var blockOffset, blockLength int64
switch {
case startBlock == endBlock:
blockOffset = offset % e.blockSize
blockLength = length
case block == startBlock:
blockOffset = offset % e.blockSize
blockLength = e.blockSize - blockOffset
case block == endBlock:
blockOffset = 0
blockLength = (offset + length) % e.blockSize
default:
blockOffset = 0
blockLength = e.blockSize
}
if blockLength == 0 {
break
}
bufs, err := reader.Read()
if err != nil {
return err
}
if err = e.DecodeDataBlocks(bufs); err != nil {
logger.LogIf(ctx, err)
return err
}
n, err := writeDataBlocks(ctx, writer, bufs, e.dataBlocks, blockOffset, blockLength)
if err != nil {
return err
}
bytesWritten += n
}
if bytesWritten != length {
logger.LogIf(ctx, errLessData)
return errLessData
}
return nil
}