Pádraig Brady wrote:
+** Improvements + + dd now supports iflag=direct with arbitrary sized files. + ** Build-related
----- What was the use-case for this? It seems it is a problematic feature: if someone uses 'direct', they aren't getting the most recent version of the file and may get random "slicing" in the file -- meaning that on-disk sectors may not (if looking at "byte-order") be contiguous. If someone has updated, say, sectors 0-127 of a file by inserting a new sentence in block 0 -- which shifts the byte stream for the whole file, but has only written back sectors 0-16, then someone doing a direct read of sectors 0-127 will see a discontinuity between sectors 16-17. If the purpose is to not wipe the memory cache with a 1-time read, they can use the madvise option to tell the OS that it shouldn't keep around sectors after they have been read. I can't think of any good use case to force reading stale sectors off of disk as they on-disk image would have no integrity if someone else is writing to the file and has only written a partial update. -l
