hesela.devValidDataLength (exFAT)
ValidDataLength is the exFAT stream field that records the initialized prefix length in bytes.
For a regular file, VDL lies between zero and DataLength. Reads in the remaining logical tail return zeros although its on-media bytes are undefined. This differs from allocation size and does not demonstrate erasure. Directories require both lengths to match. [1]
Linux v6.12 distinguishes the partially initialized block from later unwritten blocks in exfat_get_block; exfat_direct_IO handles the partial-block read tail. This is version-specific code evidence, not a mounted-volume experiment. [2]
Relations
- related
- exFAT, Allocation bitmap, File storage