From mboxrd@z Thu Jan  1 00:00:00 1970
To: 9fans@cse.psu.edu
Subject: Re: [9fans] Fossil thinks my free space is a wee bit more than it is
From: "Russ Cox" <rsc@swtch.com>
Date: Tue,  9 Oct 2007 22:23:50 -0400
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The fix should be to edit the bottom of
/sys/src/cmd/fossil/cache.c:/^doRemoveLink
changing

	l.epochClose = p->epoch;
	blockSetLabel(b, &l, 0);

to

	l.epochClose = p->epoch;
	if(l.epochClose == l.epoch){
		vtLock(c->fl->lk);
		if(l.epoch == c->fl->epochlow)
			c->fl->nused--;
		blockSetLabel(b, &l, 0);
		vtUnlock(c->fl->lk);
	}else
		blockSetLabel(b, &l, 0);

Untested.

Treating l.epoch == l.epochClose as meaning the block is free
is an optimization that allows fossil to reclaim space allocated
and then discarded in the same snapshot.  The nused tracking
code was not changed when the optimization got added, 
causing the misreported use numbers.

Also, you can delete u32int nfree; from struct FreeList.
It is never accessed.

Russ