I keep wondering if this assertion of code difference or lack thereof can be tested. Are not all these sources available? Which bits are missing? On Tue, Nov 5, 2024 at 9:55 AM Noel Chiappa <jnc(a)mercury.lcs.mit.edu> wrote:

On Tue, Nov 5, 2024 at 10:55 AM Noel Chiappa <jnc(a)mercury.lcs.mit.edu> wrote: Yes. The original unix code was copied and redone somewhat. It was still likely a derivative work (which is why AT&T forced Berkeley to redo it for 4.4-lite), but it was like 25% the same, 25% similar but functionally identical and 50% new for UFS, but filesystem layout is file system layout and some similarities persisted. 3bsd added dtofsb() calls. 4bsd added code to make accessing the indirect blocks more reliable and made writing directories more reliable. 4.1 was identical to 4bsd. 4.2 changed a lot. the 32V bmap was 112 lines long, while 4.2 was 196 lines with the following diffstat: 1 file changed, 141 insertions(+), 57 deletions(-) So by this measure, over half of the new function was new (though most of the comments were still the same). It did have the same structure, but structure isn't necessarily copyrightable since filesystem layout code will be similar between filesystems that are write-in-place. Looking at the diff, there's one stretch of 15 lines that are identical, but otherwise there's changes (mostly additions) every few lines. A substantial re-write. These days, most open source authors would replace the copyright statement with their own for such an extensive rewrite since the diff was over 2x the size of the original file (another very imperfect measure). Though the comments remaining identical is troublesome because they are the parts of the code that are the most creative and subject to the most freedom while the for loops and such are largely dictated by the problem or C language and customary style. Between 4.2 and 4.3, the changes were around the edges of this function though not in this function (I was remiss in not chasing down the bare diff I did last night). By net.2 it was re-written again, moving most of the function of bmap elsewhere, so that almost nothing remained from the original 32V in the original bmap function (though a quick grep shows that parts did move elsewhere). In net.2 it's back down to 75 lines. shorter even than in 32V (but it's a bit deceptive since the code was elsewhere, though also largely reworked). diff reports only lines '{', '}', '/*', '*/' and a few simple assignments (bap = bp->b_un.b_daddr;) and function calls (brelse(bp)) being the same and all the comments different / gone from this function. Though a fair number of the diffs were due to changes in the "buffer cache" interface, some formatting changes and some substitution of #defines (like NIADDR) for bare constants (3 in this case). These changes were also due to the role of bmap being reduced and things like balloc being used to handle the details a fair bit differently. And bits of balloc do resemble bits of the original bmap, but again the structure had changed somewhat. The numbers for my diffs and such are based on Krik's disks, but can also be tested by looking at the links I posted earlier or downloading and extracting the sources from the TUHS archive. The bmap() function I've extracted from different versions: https://people.freebsd.org/~imp/pmap/pmap.32v https://people.freebsd.org/~imp/pmap/pmap.4.2 https://people.freebsd.org/~imp/pmap/pmap.4.3 https://people.freebsd.org/~imp/pmap/pmap.net.2 Warner