[Info-vax] Re; Spiralog, RMS Journaling (was Re: FREESPADRIFT)

[Johnny Billquist]

On 2016-06-30 09:15, lawrencedo99 at gmail.com wrote:
> On Wednesday, June 29, 2016 at 10:57:55 PM UTC+12, Johnny Billquist wrote:
>> On 2016-06-29 12:04, Lawrence D’Oliveiro wrote:
>>> Have you noticed that, on modern Linux systems, fsck invocations don’t
>>> need to happen that often? Yet your proposal would require them to happen
>>> much more frequently, even without abnormal shutdowns? Namely, you now
>>> have to have them as a regular part of normal system operation?
>>
>> Nothing bad happens if you do them more infrequently in this situation.
>> You just have some files/directories that you deleted, whose space on
>> the disk have not been reclaimed yet.
>
> OK, so you collect these orphaned directories into lost+found.

Whenever you go scanning for such things, yes.
Actually just the same as in VMS, where you can much more easily create 
lost files, since there isn't any reference counting on them. In VMS, 
just "unlink" the file, and there you are - a lost file.

> How do you delete them?

Delete all references to the directory, and the directory will be gone, 
obviously. Which means that something like "rm -rf foo" will do it 
properly, as it recursively first goes down and remove the entries 
inside the directory before removing the directory itself. So any 
circular reference will be broken first, and at the end, if no other 
directory would have a link, the the reference count would go to zero.

But this is all academic, as Unix systems today will not allow you to 
create random hard links to directories anyway. But the reason is not 
because of any cyclic issues. In fact, you have cycles everywhere.

How about /bin/../bin/../bin/../bin/../bin/..   (Feel free to continue 
that path pattern as long as you want, except that it will be refused 
when you go over MAXPATHLENGTH0.)
Of course the file system integrity was not violated because of this 
cycle... Because a cycle does not violate the file system integrity.

	Johnny