shithub: gefs

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snap: stop playing games with re-enqueing blocks

this is inherently racy, and we probably don't want to be
modifying a block that we're in the process of writing back;
stop doing it, and instead ither enqueue and nil it out, or
mutate the block in place synchronously.

--- a/snap.c

+++ b/snap.c

@@ -15,11 +15,9 @@

 	if(dl->ins == nil)

 		return;

-	if(!checkflag(dl->ins, Bdirty))

-		return;

-

 	traceb("dlflush", dl->ins->bp);

 	enqueue(dl->ins);

+	dl->ins = nil;

 	m.op = Oinsert;

 	dlist2kv(dl, &m, kvbuf, sizeof(kvbuf));

 	btupsert(&fs->snap, &m, 1);

@@ -209,15 +207,15 @@

 		if(d->ins != nil)

 			holdblk(d->ins);

 	}else{

-		if(m->ins != nil && checkflag(m->ins, Bdirty))

+		if(m->ins != nil){

 			enqueue(m->ins);

-		if(d->tl.addr == d->ins->bp.addr)

-			b = holdblk(d->ins);

-		else

-			b = getblk(d->tl, 0);

+			dropblk(m->ins);

+			m->ins = nil;

+		}

+		b = getblk(d->tl, 0);

 		b->logp = m->hd;

-		setflag(b, Bdirty);

-		enqueue(b);

+		finalize(b);

+		syncblk(b);

 		dropblk(b);

 	}

 	msg[0].op = Odelete;

@@ -562,7 +560,7 @@

 	}

 	if(dl->ins == nil || Logspc - dl->ins->logsz < Logslop){

 		b = newblk(&fs->snap, Tdlist, 0);

-		if(dl->ins != nil && checkflag(b, Bdirty))

+		if(dl->ins != nil)

 			enqueue(dl->ins);

 		if(dl->tl.addr == -1)

 			dl->tl = b->bp;