shithub: gefs

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quiesce: fix race

if the writer deferred frees between the quiesce and grabbing/trimming
the freelist, we could free blocks from the next epoch, which would
be bad.

--- a/blk.c

+++ b/blk.c

@@ -902,22 +902,21 @@

 		if(fs->active[i] == fs->lastactive[i])

 			allquiesced = 0;

 	}

-	if(allquiesced)

+	p = nil;

+	if(allquiesced){

+		inc64(&fs->qgen, 1);

 		for(i = 0; i < fs->nquiesce; i++)

 			fs->lastactive[i] = fs->active[i];

-	unlock(&fs->activelk);

-	if(!allquiesced)

-		return;

-	inc64(&fs->qgen, 1);

-	lock(&fs->freelk);

-	p = nil;

-	if(fs->freep != nil){

-		p = fs->freep->next;

-		fs->freep->next = nil;

+		lock(&fs->freelk);

+		if(fs->freep != nil){

+			p = fs->freep->next;

+			fs->freep->next = nil;

+		}

+		fs->freep = fs->freehd;

+		unlock(&fs->freelk);

 	}

-	fs->freep = fs->freehd;

-	unlock(&fs->freelk);

+	unlock(&fs->activelk);

 	while(p != nil){

 		n = p->next;