[TUHS] moving directories in svr2

[Bakul Shah]

On Dec 29, 2021, at 7:45 PM, Noel Chiappa <jnc at mercury.lcs.mit.edu> wrote:
> 
>> From: Bakul Shah
> 
>> My guess is *not* storing a path instead of a ptr to the inode was done
>> to save on memory.
> 
> More probably speed; those old disks were not fast, and on a PDP-11, disk
> caches were so small that converting the path to the current directory to its
> in memory inode could take a bunch of disk reads.

Good point!

>> Every inode has a linkcount so detecting when the last conn. is severed
>> not a problem.
> 
> Depends; if a directory _has_ to be empty before it can be deleted, maybe; but
> if not, no. (Consider if /a/b/c/d exists, and /a/b is removed; the tree
> underneath it has to be walked and the components deleted. That could take a
> while...) In the general case (e.g. without the restriction to a tree), it's
> basically the same problem as garbage collection in LISP.

Indeed. You can detect circularly linked nodes when you try to delete
sub directories. Then you have to ask the user whether to still delete it!
In Lisp you can simply NIL a node and let the GC take care of it.... May be
you can do the same with "rm -rf" but it may have a surprising/unintended
outcome! An important point I missed. Thanks.

> 
> 	  Noel