forked from TrueCloudLab/restic
116 lines
2.6 KiB
Go
116 lines
2.6 KiB
Go
package restorer
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import (
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"os"
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"sync"
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"github.com/cespare/xxhash/v2"
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"github.com/restic/restic/internal/debug"
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)
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// writes blobs to target files.
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// multiple files can be written to concurrently.
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// multiple blobs can be concurrently written to the same file.
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// TODO I am not 100% convinced this is necessary, i.e. it may be okay
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// to use multiple os.File to write to the same target file
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type filesWriter struct {
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buckets []filesWriterBucket
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}
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type filesWriterBucket struct {
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lock sync.Mutex
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files map[string]*partialFile
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}
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type partialFile struct {
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*os.File
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users int // Reference count.
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sparse bool
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}
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func newFilesWriter(count int) *filesWriter {
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buckets := make([]filesWriterBucket, count)
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for b := 0; b < count; b++ {
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buckets[b].files = make(map[string]*partialFile)
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}
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return &filesWriter{
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buckets: buckets,
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}
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}
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func (w *filesWriter) writeToFile(path string, blob []byte, offset int64, createSize int64, sparse bool) error {
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bucket := &w.buckets[uint(xxhash.Sum64String(path))%uint(len(w.buckets))]
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acquireWriter := func() (*partialFile, error) {
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bucket.lock.Lock()
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defer bucket.lock.Unlock()
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if wr, ok := bucket.files[path]; ok {
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bucket.files[path].users++
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return wr, nil
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}
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var flags int
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if createSize >= 0 {
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flags = os.O_CREATE | os.O_TRUNC | os.O_WRONLY
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} else {
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flags = os.O_WRONLY
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}
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f, err := os.OpenFile(path, flags, 0600)
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if err != nil {
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return nil, err
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}
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wr := &partialFile{File: f, users: 1, sparse: sparse}
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bucket.files[path] = wr
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if createSize >= 0 {
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if sparse {
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err = truncateSparse(f, createSize)
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if err != nil {
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return nil, err
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}
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} else {
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err := preallocateFile(wr.File, createSize)
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if err != nil {
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// Just log the preallocate error but don't let it cause the restore process to fail.
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// Preallocate might return an error if the filesystem (implementation) does not
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// support preallocation or our parameters combination to the preallocate call
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// This should yield a syscall.ENOTSUP error, but some other errors might also
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// show up.
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debug.Log("Failed to preallocate %v with size %v: %v", path, createSize, err)
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}
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}
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}
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return wr, nil
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}
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releaseWriter := func(wr *partialFile) error {
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bucket.lock.Lock()
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defer bucket.lock.Unlock()
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if bucket.files[path].users == 1 {
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delete(bucket.files, path)
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return wr.Close()
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}
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bucket.files[path].users--
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return nil
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}
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wr, err := acquireWriter()
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if err != nil {
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return err
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}
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_, err = wr.WriteAt(blob, offset)
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if err != nil {
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// ignore subsequent errors
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_ = releaseWriter(wr)
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return err
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}
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return releaseWriter(wr)
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}
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