shithub: gefs

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snap: add a special-case snap deadlist for the snap tree

we need to log the snap tree blocks somewhere, so that we
can avoid them getting clobbered. Put this into the superblock,
and reclaim it on snap sync.

--- a/blk.c

+++ b/blk.c

@@ -944,7 +944,7 @@

 	Bfree *f;

 	ulong ge;

-	if(t != nil && t != &fs->snap && bp.gen <= t->prev){

+	if(t == &fs->snap || (t != nil && bp.gen <= t->prev)){

 		killblk(t, bp);

 		return;

 	}

@@ -1246,5 +1246,10 @@

 			sysfatal("sync arena: %r");

 		unlock(a);

 	}

+	freedl(&fs->snapdl, 1);

+	fs->snapdl.hd.addr = -1;

+	fs->snapdl.hd.hash = -1;

+	fs->snapdl.tl.addr = -1;

+	fs->snapdl.tl.hash = -1;

 	qunlock(&fs->synclk);

 }

--- a/dat.h

+++ b/dat.h

@@ -458,6 +458,7 @@

 	int	blksz;

 	int	bufspc;

 	Tree	snap;

+	Dlist	snapdl;

 	int	narena;

 	vlong	arenasz;

 	vlong	nextqid;

--- a/fns.h

+++ b/fns.h

@@ -66,6 +66,7 @@

 char*	updatesnap(Tree**, Tree*, char*);

 char*	labelsnap(Tree*, char*);

 char*	delsnap(Tree*, vlong, char*);

+char*	freedl(Dlist*, int);

 Tree*	opensnap(char*);

 vlong	successor(vlong);

--- a/pack.c

+++ b/pack.c

@@ -561,12 +561,16 @@

 	int i;

 	assert(sz == Blksz);

-	memcpy(p, "gefs0006", 8);	p += 8;

+	memcpy(p, "gefs0007", 8);	p += 8;

 	PACK32(p, Blksz);		p += 4;

 	PACK32(p, Bufspc);		p += 4;

 	PACK32(p, fi->snap.ht);		p += 4;

 	PACK64(p, fi->snap.bp.addr);	p += 8;

 	PACK64(p, fi->snap.bp.hash);	p += 8;

+	PACK64(p, fi->snapdl.hd.addr);	p += 8;

+	PACK64(p, fi->snapdl.hd.hash);	p += 8;

+	PACK64(p, fi->snapdl.tl.addr);	p += 8;

+	PACK64(p, fi->snapdl.tl.hash);	p += 8;

 	PACK32(p, fi->narena);		p += 4;

 	PACK64(p, fi->arenasz);		p += 8;

 	PACK64(p, fi->nextqid);		p += 8;

@@ -585,21 +589,28 @@

 	int i;

 	assert(sz == Blksz);

-	if(memcmp(p, "gefs0006", 8) != 0){

+	if(memcmp(p, "gefs0007", 8) != 0){

 		werrstr("wrong block header %.8s\n", p);

 		return nil;

 	}

 	p += 8;

-	fi->blksz = UNPACK32(p);	p += 4;

-	fi->bufspc = UNPACK32(p);	p += 4;

-	fi->snap.ht = UNPACK32(p);	p += 4;

-	fi->snap.bp.addr = UNPACK64(p);	p += 8;

-	fi->snap.bp.hash = UNPACK64(p);	p += 8;

-	fi->snap.bp.gen = -1;		p += 0;

-	fi->narena = UNPACK32(p);	p += 4;

-	fi->arenasz = UNPACK64(p);	p += 8;

-	fi->nextqid = UNPACK64(p);	p += 8;

-	fi->nextgen = UNPACK64(p);	p += 8;

+	fi->blksz = UNPACK32(p);		p += 4;

+	fi->bufspc = UNPACK32(p);		p += 4;

+	fi->snap.ht = UNPACK32(p);		p += 4;

+	fi->snap.bp.addr = UNPACK64(p);		p += 8;

+	fi->snap.bp.hash = UNPACK64(p);		p += 8;

+	fi->snap.bp.gen = -1;			p += 0;

+	fi->snapdl.hd.addr = UNPACK64(p);	p += 8;

+	fi->snapdl.hd.hash = UNPACK64(p);	p += 8;

+	fi->snapdl.gen = -1;			p += 0;

+	fi->snapdl.tl.addr = UNPACK64(p);	p += 8;

+	fi->snapdl.tl.hash = UNPACK64(p);	p += 8;

+	fi->snapdl.gen = -1;			p += 0;

+	fi->snapdl.gen = 

+	fi->narena = UNPACK32(p);		p += 4;

+	fi->arenasz = UNPACK64(p);		p += 8;

+	fi->nextqid = UNPACK64(p);		p += 8;

+	fi->nextgen = UNPACK64(p);		p += 8;

 	fi->qgen = UNPACK64(p);	p += 8;

 	fi->arenabp = malloc(fi->narena * sizeof(Bptr));

 	for(i = 0; i < fi->narena; i++){

--- a/ream.c

+++ b/ream.c

@@ -351,6 +351,10 @@

 	fs->snap.bp = tb->bp;

 	fs->snap.ht = 1;

+	fs->snapdl.hd.addr = -1;

+	fs->snapdl.hd.hash = -1;

+	fs->snapdl.tl.addr = -1;

+	fs->snapdl.tl.hash = -1;

 	fs->nextqid = Nreamqid;

 	dropblk(mb);

--- a/snap.c

+++ b/snap.c

@@ -140,7 +140,7 @@

 	}

 }

-static char*

+char*

 freedl(Dlist *dl, int docontents)

 {

 	Bptr bp;

@@ -532,7 +532,9 @@

 	Blk *b;

 	char *p;

-	if((dl = getdl(t->gen, bp.gen)) == nil)

+	if(t == &fs->snap)

+		dl = &fs->snapdl;

+	else if((dl = getdl(t->gen, bp.gen)) == nil)

 		return -1;

 	if(dl->ins == nil || dl->ins->deadsz == Dlspc){

 		if((b = newblk(&fs->snap, Tdlist)) == nil){