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  1. package mount
  2. import (
  3. "context"
  4. "syscall"
  5. "github.com/hanwen/go-fuse/v2/fuse"
  6. "github.com/seaweedfs/seaweedfs/weed/filer"
  7. "github.com/seaweedfs/seaweedfs/weed/glog"
  8. )
  9. // These are non-POSIX extensions
  10. const (
  11. SEEK_DATA uint32 = 3 // seek to next data after the offset
  12. SEEK_HOLE uint32 = 4 // seek to next hole after the offset
  13. ENXIO = fuse.Status(syscall.ENXIO)
  14. )
  15. // Lseek finds next data or hole segments after the specified offset
  16. // See https://man7.org/linux/man-pages/man2/lseek.2.html
  17. func (wfs *WFS) Lseek(cancel <-chan struct{}, in *fuse.LseekIn, out *fuse.LseekOut) fuse.Status {
  18. // not a documented feature
  19. if in.Padding != 0 {
  20. return fuse.EINVAL
  21. }
  22. if in.Whence != SEEK_DATA && in.Whence != SEEK_HOLE {
  23. return fuse.EINVAL
  24. }
  25. // file must exist
  26. fh := wfs.GetHandle(FileHandleId(in.Fh))
  27. if fh == nil {
  28. return fuse.EBADF
  29. }
  30. // lock the file until the proper offset was calculated
  31. fh.orderedMutex.Acquire(context.Background(), 1)
  32. defer fh.orderedMutex.Release(1)
  33. fileSize := int64(filer.FileSize(fh.GetEntry()))
  34. offset := max(int64(in.Offset), 0)
  35. glog.V(4).Infof(
  36. "Lseek %s fh %d in [%d,%d], whence %d",
  37. fh.FullPath(), fh.fh, offset, fileSize, in.Whence,
  38. )
  39. // can neither seek beyond file nor seek to a hole at the end of the file with SEEK_DATA
  40. if offset > fileSize {
  41. return ENXIO
  42. } else if in.Whence == SEEK_DATA && offset == fileSize {
  43. return ENXIO
  44. }
  45. // refresh view cache if necessary
  46. if fh.entryViewCache == nil {
  47. var err error
  48. fh.entryViewCache, err = filer.NonOverlappingVisibleIntervals(fh.wfs.LookupFn(), fh.entry.GetChunks(), 0, fileSize)
  49. if err != nil {
  50. return fuse.EIO
  51. }
  52. }
  53. // search chunks for the offset
  54. found, offset := searchChunks(fh, offset, fileSize, in.Whence)
  55. if found {
  56. out.Offset = uint64(offset)
  57. return fuse.OK
  58. }
  59. // in case we found no exact matches, we return the recommended fallbacks, that is:
  60. // original offset for SEEK_DATA or end of file for an implicit hole
  61. if in.Whence == SEEK_DATA {
  62. out.Offset = in.Offset
  63. } else {
  64. out.Offset = uint64(fileSize)
  65. }
  66. return fuse.OK
  67. }
  68. // searchChunks goes through all chunks to find the correct offset
  69. func searchChunks(fh *FileHandle, offset, fileSize int64, whence uint32) (found bool, out int64) {
  70. chunkViews := filer.ViewFromVisibleIntervals(fh.entryViewCache, offset, fileSize)
  71. for _, chunkView := range chunkViews {
  72. if offset < chunkView.LogicOffset {
  73. if whence == SEEK_HOLE {
  74. out = offset
  75. } else {
  76. out = chunkView.LogicOffset
  77. }
  78. return true, out
  79. }
  80. if offset >= chunkView.LogicOffset && offset < chunkView.Offset+int64(chunkView.Size) && whence == SEEK_DATA {
  81. out = offset
  82. return true, out
  83. }
  84. offset += int64(chunkView.Size)
  85. }
  86. return
  87. }