weedfs_file_lseek.go 1.8 KB

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  1. package mount
  2. import (
  3. "syscall"
  4. "github.com/hanwen/go-fuse/v2/fuse"
  5. "github.com/seaweedfs/seaweedfs/weed/filer"
  6. "github.com/seaweedfs/seaweedfs/weed/glog"
  7. )
  8. // These are non-POSIX extensions
  9. const (
  10. SEEK_DATA uint32 = 3 // seek to next data after the offset
  11. SEEK_HOLE uint32 = 4 // seek to next hole after the offset
  12. ENXIO = fuse.Status(syscall.ENXIO)
  13. )
  14. // Lseek finds next data or hole segments after the specified offset
  15. // See https://man7.org/linux/man-pages/man2/lseek.2.html
  16. func (wfs *WFS) Lseek(cancel <-chan struct{}, in *fuse.LseekIn, out *fuse.LseekOut) fuse.Status {
  17. // not a documented feature
  18. if in.Padding != 0 {
  19. return fuse.EINVAL
  20. }
  21. if in.Whence != SEEK_DATA && in.Whence != SEEK_HOLE {
  22. return fuse.EINVAL
  23. }
  24. // file must exist
  25. fh := wfs.GetHandle(FileHandleId(in.Fh))
  26. if fh == nil {
  27. return fuse.EBADF
  28. }
  29. // lock the file until the proper offset was calculated
  30. fh.RLock()
  31. defer fh.RUnlock()
  32. fh.entryLock.RLock()
  33. defer fh.entryLock.RUnlock()
  34. fileSize := int64(filer.FileSize(fh.GetEntry()))
  35. offset := max(int64(in.Offset), 0)
  36. glog.V(4).Infof(
  37. "Lseek %s fh %d in [%d,%d], whence %d",
  38. fh.FullPath(), fh.fh, offset, fileSize, in.Whence,
  39. )
  40. // can neither seek beyond file nor seek to a hole at the end of the file with SEEK_DATA
  41. if offset > fileSize {
  42. return ENXIO
  43. } else if in.Whence == SEEK_DATA && offset == fileSize {
  44. return ENXIO
  45. }
  46. // search chunks for the offset
  47. found, offset := fh.entryChunkGroup.SearchChunks(offset, fileSize, in.Whence)
  48. if found {
  49. out.Offset = uint64(offset)
  50. return fuse.OK
  51. }
  52. // in case we found no exact matches, we return the recommended fallbacks, that is:
  53. // original offset for SEEK_DATA or end of file for an implicit hole
  54. if in.Whence == SEEK_DATA {
  55. out.Offset = in.Offset
  56. } else {
  57. out.Offset = uint64(fileSize)
  58. }
  59. return fuse.OK
  60. }