Import sources from 2011-03-30 iso image

1 files changed, 931 insertions, 0 deletions

diff --git a/sys/src/cmd/venti/srv/arena.c b/sys/src/cmd/venti/srv/arena.c
new file mode 100755
index 000000000..2a176cded
--- /dev/null
+++ b/sys/src/cmd/venti/srv/arena.c
@@ -0,0 +1,931 @@
+#include "stdinc.h"
+#include "dat.h"
+#include "fns.h"
+
+typedef struct ASum ASum;
+
+struct ASum
+{
+	Arena	*arena;
+	ASum	*next;
+};
+
+static void	sealarena(Arena *arena);
+static int	okarena(Arena *arena);
+static int	loadarena(Arena *arena);
+static CIBlock	*getcib(Arena *arena, int clump, int writing, CIBlock *rock);
+static void	putcib(Arena *arena, CIBlock *cib);
+static void	sumproc(void *);
+static void loadcig(Arena *arena);
+
+static QLock	sumlock;
+static Rendez	sumwait;
+static ASum	*sumq;
+static ASum	*sumqtail;
+static uchar zero[8192];
+
+int	arenasumsleeptime;
+
+int
+initarenasum(void)
+{
+	needzeroscore();  /* OS X */
+
+	sumwait.l = &sumlock;
+
+	if(vtproc(sumproc, nil) < 0){
+		seterr(EOk, "can't start arena checksum slave: %r");
+		return -1;
+	}
+	return 0;
+}
+
+/*
+ * make an Arena, and initialize it based upon the disk header and trailer.
+ */
+Arena*
+initarena(Part *part, u64int base, u64int size, u32int blocksize)
+{
+	Arena *arena;
+
+	arena = MKZ(Arena);
+	arena->part = part;
+	arena->blocksize = blocksize;
+	arena->clumpmax = arena->blocksize / ClumpInfoSize;
+	arena->base = base + blocksize;
+	arena->size = size - 2 * blocksize;
+
+	if(loadarena(arena) < 0){
+		seterr(ECorrupt, "arena header or trailer corrupted");
+		freearena(arena);
+		return nil;
+	}
+	if(okarena(arena) < 0){
+		freearena(arena);
+		return nil;
+	}
+
+	if(arena->diskstats.sealed && scorecmp(zeroscore, arena->score)==0)
+		sealarena(arena);
+
+	return arena;
+}
+
+void
+freearena(Arena *arena)
+{
+	if(arena == nil)
+		return;
+	free(arena);
+}
+
+Arena*
+newarena(Part *part, u32int vers, char *name, u64int base, u64int size, u32int blocksize)
+{
+	int bsize;
+	Arena *arena;
+
+	if(nameok(name) < 0){
+		seterr(EOk, "illegal arena name", name);
+		return nil;
+	}
+	arena = MKZ(Arena);
+	arena->part = part;
+	arena->version = vers;
+	if(vers == ArenaVersion4)
+		arena->clumpmagic = _ClumpMagic;
+	else{
+		do
+			arena->clumpmagic = fastrand();
+		while(arena->clumpmagic==_ClumpMagic || arena->clumpmagic==0);
+	}
+	arena->blocksize = blocksize;
+	arena->clumpmax = arena->blocksize / ClumpInfoSize;
+	arena->base = base + blocksize;
+	arena->size = size - 2 * blocksize;
+
+	namecp(arena->name, name);
+
+	bsize = sizeof zero;
+	if(bsize > arena->blocksize)
+		bsize = arena->blocksize;
+
+	if(wbarena(arena)<0 || wbarenahead(arena)<0
+	|| writepart(arena->part, arena->base, zero, bsize)<0){
+		freearena(arena);
+		return nil;
+	}
+
+	return arena;
+}
+
+int
+readclumpinfo(Arena *arena, int clump, ClumpInfo *ci)
+{
+	CIBlock *cib, r;
+
+	cib = getcib(arena, clump, 0, &r);
+	if(cib == nil)
+		return -1;
+	unpackclumpinfo(ci, &cib->data->data[cib->offset]);
+	putcib(arena, cib);
+	return 0;
+}
+
+int
+readclumpinfos(Arena *arena, int clump, ClumpInfo *cis, int n)
+{
+	CIBlock *cib, r;
+	int i;
+
+	/*
+	 * because the clump blocks are laid out
+	 * in reverse order at the end of the arena,
+	 * it can be a few percent faster to read
+	 * the clumps backwards, which reads the
+	 * disk blocks forwards.
+	 */
+	for(i = n-1; i >= 0; i--){
+		cib = getcib(arena, clump + i, 0, &r);
+		if(cib == nil){
+			n = i;
+			continue;
+		}
+		unpackclumpinfo(&cis[i], &cib->data->data[cib->offset]);
+		putcib(arena, cib);
+	}
+	return n;
+}
+
+/*
+ * write directory information for one clump
+ * must be called the arena locked
+ */
+int
+writeclumpinfo(Arena *arena, int clump, ClumpInfo *ci)
+{
+	CIBlock *cib, r;
+
+	cib = getcib(arena, clump, 1, &r);
+	if(cib == nil)
+		return -1;
+	dirtydblock(cib->data, DirtyArenaCib);
+	packclumpinfo(ci, &cib->data->data[cib->offset]);
+	putcib(arena, cib);
+	return 0;
+}
+
+u64int
+arenadirsize(Arena *arena, u32int clumps)
+{
+	return ((clumps / arena->clumpmax) + 1) * arena->blocksize;
+}
+
+/*
+ * read a clump of data
+ * n is a hint of the size of the data, not including the header
+ * make sure it won't run off the end, then return the number of bytes actually read
+ */
+u32int
+readarena(Arena *arena, u64int aa, u8int *buf, long n)
+{
+	DBlock *b;
+	u64int a;
+	u32int blocksize, off, m;
+	long nn;
+
+	if(n == 0)
+		return -1;
+
+	qlock(&arena->lock);
+	a = arena->size - arenadirsize(arena, arena->memstats.clumps);
+	qunlock(&arena->lock);
+	if(aa >= a){
+		seterr(EOk, "reading beyond arena clump storage: clumps=%d aa=%lld a=%lld -1 clumps=%lld\n", arena->memstats.clumps, aa, a, arena->size - arenadirsize(arena, arena->memstats.clumps - 1));
+		return -1;
+	}
+	if(aa + n > a)
+		n = a - aa;
+
+	blocksize = arena->blocksize;
+	a = arena->base + aa;
+	off = a & (blocksize - 1);
+	a -= off;
+	nn = 0;
+	for(;;){
+		b = getdblock(arena->part, a, OREAD);
+		if(b == nil)
+			return -1;
+		m = blocksize - off;
+		if(m > n - nn)
+			m = n - nn;
+		memmove(&buf[nn], &b->data[off], m);
+		putdblock(b);
+		nn += m;
+		if(nn == n)
+			break;
+		off = 0;
+		a += blocksize;
+	}
+	return n;
+}
+
+/*
+ * write some data to the clump section at a given offset
+ * used to fix up corrupted arenas.
+ */
+u32int
+writearena(Arena *arena, u64int aa, u8int *clbuf, u32int n)
+{
+	DBlock *b;
+	u64int a;
+	u32int blocksize, off, m;
+	long nn;
+	int ok;
+
+	if(n == 0)
+		return -1;
+
+	qlock(&arena->lock);
+	a = arena->size - arenadirsize(arena, arena->memstats.clumps);
+	if(aa >= a || aa + n > a){
+		qunlock(&arena->lock);
+		seterr(EOk, "writing beyond arena clump storage");
+		return -1;
+	}
+
+	blocksize = arena->blocksize;
+	a = arena->base + aa;
+	off = a & (blocksize - 1);
+	a -= off;
+	nn = 0;
+	for(;;){
+		b = getdblock(arena->part, a, off != 0 || off + n < blocksize ? ORDWR : OWRITE);
+		if(b == nil){
+			qunlock(&arena->lock);
+			return -1;
+		}
+		dirtydblock(b, DirtyArena);
+		m = blocksize - off;
+		if(m > n - nn)
+			m = n - nn;
+		memmove(&b->data[off], &clbuf[nn], m);
+		ok = 0;
+		putdblock(b);
+		if(ok < 0){
+			qunlock(&arena->lock);
+			return -1;
+		}
+		nn += m;
+		if(nn == n)
+			break;
+		off = 0;
+		a += blocksize;
+	}
+	qunlock(&arena->lock);
+	return n;
+}
+
+/*
+ * allocate space for the clump and write it,
+ * updating the arena directory
+ZZZ question: should this distinguish between an arena
+filling up and real errors writing the clump?
+ */
+u64int
+writeaclump(Arena *arena, Clump *c, u8int *clbuf)
+{
+	DBlock *b;
+	u64int a, aa;
+	u32int clump, n, nn, m, off, blocksize;
+	int ok;
+
+	n = c->info.size + ClumpSize + U32Size;
+	qlock(&arena->lock);
+	aa = arena->memstats.used;
+	if(arena->memstats.sealed
+	|| aa + n + U32Size + arenadirsize(arena, arena->memstats.clumps + 1) > arena->size){
+		if(!arena->memstats.sealed){
+			logerr(EOk, "seal memstats %s", arena->name);
+			arena->memstats.sealed = 1;
+			wbarena(arena);
+		}
+		qunlock(&arena->lock);
+		return TWID64;
+	}
+	if(packclump(c, &clbuf[0], arena->clumpmagic) < 0){
+		qunlock(&arena->lock);
+		return TWID64;
+	}
+
+	/*
+	 * write the data out one block at a time
+	 */
+	blocksize = arena->blocksize;
+	a = arena->base + aa;
+	off = a & (blocksize - 1);
+	a -= off;
+	nn = 0;
+	for(;;){
+		b = getdblock(arena->part, a, off != 0 ? ORDWR : OWRITE);
+		if(b == nil){
+			qunlock(&arena->lock);
+			return TWID64;
+		}
+		dirtydblock(b, DirtyArena);
+		m = blocksize - off;
+		if(m > n - nn)
+			m = n - nn;
+		memmove(&b->data[off], &clbuf[nn], m);
+		ok = 0;
+		putdblock(b);
+		if(ok < 0){
+			qunlock(&arena->lock);
+			return TWID64;
+		}
+		nn += m;
+		if(nn == n)
+			break;
+		off = 0;
+		a += blocksize;
+	}
+
+	arena->memstats.used += c->info.size + ClumpSize;
+	arena->memstats.uncsize += c->info.uncsize;
+	if(c->info.size < c->info.uncsize)
+		arena->memstats.cclumps++;
+
+	clump = arena->memstats.clumps;
+	if(clump % ArenaCIGSize == 0){
+		if(arena->cig == nil){
+			loadcig(arena);
+			if(arena->cig == nil)
+				goto NoCIG;
+		}
+		/* add aa as start of next cig */
+		if(clump/ArenaCIGSize != arena->ncig){
+			fprint(2, "bad arena cig computation %s: writing clump %d but %d cigs\n",
+				arena->name, clump, arena->ncig);
+			arena->ncig = -1;
+			vtfree(arena->cig);
+			arena->cig = nil;
+			goto NoCIG;
+		}
+		arena->cig = vtrealloc(arena->cig, (arena->ncig+1)*sizeof arena->cig[0]);
+		arena->cig[arena->ncig++].offset = aa;
+	}
+NoCIG:
+	arena->memstats.clumps++;
+
+	if(arena->memstats.clumps == 0)
+		sysfatal("clumps wrapped");
+	arena->wtime = now();
+	if(arena->ctime == 0)
+		arena->ctime = arena->wtime;
+
+	writeclumpinfo(arena, clump, &c->info);
+	wbarena(arena);
+
+	qunlock(&arena->lock);
+
+	return aa;
+}
+
+int
+atailcmp(ATailStats *a, ATailStats *b)
+{
+	/* good test */
+	if(a->used < b->used)
+		return -1;
+	if(a->used > b->used)
+		return 1;
+		
+	/* suspect tests - why order this way? (no one cares) */
+	if(a->clumps < b->clumps)
+		return -1;
+	if(a->clumps > b->clumps)
+		return 1;
+	if(a->cclumps < b->cclumps)
+		return -1;
+	if(a->cclumps > b->cclumps)
+		return 1;
+	if(a->uncsize < b->uncsize)
+		return -1;
+	if(a->uncsize > b->uncsize)
+		return 1;
+	if(a->sealed < b->sealed)
+		return -1;
+	if(a->sealed > b->sealed)
+		return 1;
+		
+	/* everything matches */
+	return 0;
+}
+
+void
+setatailstate(AState *as)
+{
+	int i, j, osealed;
+	Arena *a;
+	Index *ix;
+
+	trace(0, "setatailstate %s 0x%llux clumps %d", as->arena->name, as->aa, as->stats.clumps);
+
+	/*
+	 * Look up as->arena to find index.
+	 */
+	needmainindex();	/* OS X linker */
+	ix = mainindex;
+	for(i=0; i<ix->narenas; i++)
+		if(ix->arenas[i] == as->arena)
+			break;
+	if(i==ix->narenas || as->aa < ix->amap[i].start || as->aa >= ix->amap[i].stop || as->arena != ix->arenas[i]){
+		fprint(2, "funny settailstate 0x%llux\n", as->aa);
+		return;
+	}
+
+	for(j=0; j<=i; j++){
+		a = ix->arenas[j];
+		if(atailcmp(&a->diskstats, &a->memstats) == 0)
+			continue;
+		qlock(&a->lock);
+		osealed = a->diskstats.sealed;
+		if(j == i)
+			a->diskstats = as->stats;
+		else
+			a->diskstats = a->memstats;
+		wbarena(a);
+		if(a->diskstats.sealed != osealed && !a->inqueue)
+			sealarena(a);
+		qunlock(&a->lock);
+	}
+}
+
+/*
+ * once sealed, an arena never has any data added to it.
+ * it should only be changed to fix errors.
+ * this also syncs the clump directory.
+ */
+static void
+sealarena(Arena *arena)
+{
+	arena->inqueue = 1;
+	backsumarena(arena);
+}
+
+void
+backsumarena(Arena *arena)
+{
+	ASum *as;
+
+	if(sumwait.l == nil)
+		return;
+
+	as = MK(ASum);
+	if(as == nil)
+		return;
+	qlock(&sumlock);
+	as->arena = arena;
+	as->next = nil;
+	if(sumq)
+		sumqtail->next = as;
+	else
+		sumq = as;
+	sumqtail = as;
+	rwakeup(&sumwait);
+	qunlock(&sumlock);
+}
+
+static void
+sumproc(void *unused)
+{
+	ASum *as;
+	Arena *arena;
+
+	USED(unused);
+
+	for(;;){
+		qlock(&sumlock);
+		while(sumq == nil)
+			rsleep(&sumwait);
+		as = sumq;
+		sumq = as->next;
+		qunlock(&sumlock);
+		arena = as->arena;
+		free(as);
+
+		sumarena(arena);
+	}
+}
+
+void
+sumarena(Arena *arena)
+{
+	ZBlock *b;
+	DigestState s;
+	u64int a, e;
+	u32int bs;
+	int t;
+	u8int score[VtScoreSize];
+
+	bs = MaxIoSize;
+	if(bs < arena->blocksize)
+		bs = arena->blocksize;
+
+	/*
+	 * read & sum all blocks except the last one
+	 */
+	flushdcache();
+	memset(&s, 0, sizeof s);
+	b = alloczblock(bs, 0, arena->part->blocksize);
+	e = arena->base + arena->size;
+	for(a = arena->base - arena->blocksize; a + arena->blocksize <= e; a += bs){
+		disksched();
+		while((t=arenasumsleeptime) == SleepForever){
+			sleep(1000);
+			disksched();
+		}
+		sleep(t);
+		if(a + bs > e)
+			bs = arena->blocksize;
+		if(readpart(arena->part, a, b->data, bs) < 0)
+			goto ReadErr;
+		addstat(StatSumRead, 1);
+		addstat(StatSumReadBytes, bs);
+		sha1(b->data, bs, nil, &s);
+	}
+
+	/*
+	 * the last one is special, since it may already have the checksum included
+	 */
+	bs = arena->blocksize;
+	if(readpart(arena->part, e, b->data, bs) < 0){
+ReadErr:
+		logerr(EOk, "sumarena can't sum %s, read at %lld failed: %r", arena->name, a);
+		freezblock(b);
+		return;
+	}
+	addstat(StatSumRead, 1);
+	addstat(StatSumReadBytes, bs);
+
+	sha1(b->data, bs-VtScoreSize, nil, &s);
+	sha1(zeroscore, VtScoreSize, nil, &s);
+	sha1(nil, 0, score, &s);
+	
+	/*
+	 * check for no checksum or the same
+	 */
+	if(scorecmp(score, &b->data[bs - VtScoreSize]) != 0
+	&& scorecmp(zeroscore, &b->data[bs - VtScoreSize]) != 0)
+		logerr(EOk, "overwriting mismatched checksums for arena=%s, found=%V calculated=%V",
+			arena->name, &b->data[bs - VtScoreSize], score);
+	freezblock(b);
+
+	qlock(&arena->lock);
+	scorecp(arena->score, score);
+	wbarena(arena);
+	qunlock(&arena->lock);
+}
+
+/*
+ * write the arena trailer block to the partition
+ */
+int
+wbarena(Arena *arena)
+{
+	DBlock *b;
+	int bad;
+
+	if((b = getdblock(arena->part, arena->base + arena->size, OWRITE)) == nil){
+		logerr(EAdmin, "can't write arena trailer: %r");
+		return -1;
+	}
+	dirtydblock(b, DirtyArenaTrailer);
+	bad = okarena(arena)<0 || packarena(arena, b->data)<0;
+	scorecp(b->data + arena->blocksize - VtScoreSize, arena->score);
+	putdblock(b);
+	if(bad)
+		return -1;
+	return 0;
+}
+
+int
+wbarenahead(Arena *arena)
+{
+	ZBlock *b;
+	ArenaHead head;
+	int bad;
+
+	namecp(head.name, arena->name);
+	head.version = arena->version;
+	head.size = arena->size + 2 * arena->blocksize;
+	head.blocksize = arena->blocksize;
+	head.clumpmagic = arena->clumpmagic;
+	b = alloczblock(arena->blocksize, 1, arena->part->blocksize);
+	if(b == nil){
+		logerr(EAdmin, "can't write arena header: %r");
+/* ZZZ add error message? */
+		return -1;
+	}
+	/*
+	 * this writepart is okay because it only happens
+	 * during initialization.
+	 */
+	bad = packarenahead(&head, b->data)<0 ||
+	      writepart(arena->part, arena->base - arena->blocksize, b->data, arena->blocksize)<0 ||
+	      flushpart(arena->part)<0;
+	freezblock(b);
+	if(bad)
+		return -1;
+	return 0;
+}
+
+/*
+ * read the arena header and trailer blocks from disk
+ */
+static int
+loadarena(Arena *arena)
+{
+	ArenaHead head;
+	ZBlock *b;
+
+	b = alloczblock(arena->blocksize, 0, arena->part->blocksize);
+	if(b == nil)
+		return -1;
+	if(readpart(arena->part, arena->base + arena->size, b->data, arena->blocksize) < 0){
+		freezblock(b);
+		return -1;
+	}
+	if(unpackarena(arena, b->data) < 0){
+		freezblock(b);
+		return -1;
+	}
+	if(arena->version != ArenaVersion4 && arena->version != ArenaVersion5){
+		seterr(EAdmin, "unknown arena version %d", arena->version);
+		freezblock(b);
+		return -1;
+	}
+	scorecp(arena->score, &b->data[arena->blocksize - VtScoreSize]);
+
+	if(readpart(arena->part, arena->base - arena->blocksize, b->data, arena->blocksize) < 0){
+		logerr(EAdmin, "can't read arena header: %r");
+		freezblock(b);
+		return 0;
+	}
+	if(unpackarenahead(&head, b->data) < 0)
+		logerr(ECorrupt, "corrupted arena header: %r");
+	else if(namecmp(arena->name, head.name)!=0
+	     || arena->clumpmagic != head.clumpmagic
+	     || arena->version != head.version
+	     || arena->blocksize != head.blocksize
+	     || arena->size + 2 * arena->blocksize != head.size){
+		if(namecmp(arena->name, head.name)!=0)
+			logerr(ECorrupt, "arena tail name %s head %s", 
+				arena->name, head.name);
+		else if(arena->clumpmagic != head.clumpmagic)
+			logerr(ECorrupt, "arena %d tail clumpmagic 0x%lux head 0x%lux",
+				debugarena, (ulong)arena->clumpmagic,
+				(ulong)head.clumpmagic);
+		else if(arena->version != head.version)
+			logerr(ECorrupt, "arena tail version %d head version %d",
+				arena->version, head.version);
+		else if(arena->blocksize != head.blocksize)
+			logerr(ECorrupt, "arena tail block size %d head %d",
+				arena->blocksize, head.blocksize);
+		else if(arena->size+2*arena->blocksize != head.size)
+			logerr(ECorrupt, "arena tail size %lud head %lud",
+				(ulong)arena->size+2*arena->blocksize, head.size);
+		else
+			logerr(ECorrupt, "arena header inconsistent with arena data");
+	}
+	freezblock(b);
+
+	return 0;
+}
+
+static int
+okarena(Arena *arena)
+{
+	u64int dsize;
+	int ok;
+
+	ok = 0;
+	dsize = arenadirsize(arena, arena->diskstats.clumps);
+	if(arena->diskstats.used + dsize > arena->size){
+		seterr(ECorrupt, "arena %s used > size", arena->name);
+		ok = -1;
+	}
+
+	if(arena->diskstats.cclumps > arena->diskstats.clumps)
+		logerr(ECorrupt, "arena %s has more compressed clumps than total clumps", arena->name);
+
+	/*
+	 * This need not be true if some of the disk is corrupted.
+	 *
+	if(arena->diskstats.uncsize + arena->diskstats.clumps * ClumpSize + arena->blocksize < arena->diskstats.used)
+		logerr(ECorrupt, "arena %s uncompressed size inconsistent with used space %lld %d %lld", arena->name, arena->diskstats.uncsize, arena->diskstats.clumps, arena->diskstats.used);
+	 */
+
+	/*
+	 * this happens; it's harmless.
+	 *
+	if(arena->ctime > arena->wtime)
+		logerr(ECorrupt, "arena %s creation time after last write time", arena->name);
+	 */
+	return ok;
+}
+
+static CIBlock*
+getcib(Arena *arena, int clump, int writing, CIBlock *rock)
+{
+	int mode;
+	CIBlock *cib;
+	u32int block, off;
+
+	if(clump >= arena->memstats.clumps){
+		seterr(EOk, "clump directory access out of range");
+		return nil;
+	}
+	block = clump / arena->clumpmax;
+	off = (clump - block * arena->clumpmax) * ClumpInfoSize;
+	cib = rock;
+	cib->block = block;
+	cib->offset = off;
+
+	if(writing){
+		if(off == 0 && clump == arena->memstats.clumps-1)
+			mode = OWRITE;
+		else
+			mode = ORDWR;
+	}else
+		mode = OREAD;
+
+	cib->data = getdblock(arena->part,
+		arena->base + arena->size - (block + 1) * arena->blocksize, mode);
+	if(cib->data == nil)
+		return nil;
+	return cib;
+}
+
+static void
+putcib(Arena *arena, CIBlock *cib)
+{
+	USED(arena);
+
+	putdblock(cib->data);
+	cib->data = nil;
+}
+
+
+/*
+ * For index entry readahead purposes, the arenas are 
+ * broken into smaller subpieces, called clump info groups
+ * or cigs.  Each cig has ArenaCIGSize clumps (ArenaCIGSize
+ * is chosen to make the index entries take up about half
+ * a megabyte).  The index entries do not contain enough
+ * information to determine what the clump index is for
+ * a given address in an arena.  That info is needed both for
+ * figuring out which clump group an address belongs to 
+ * and for prefetching a clump group's index entries from
+ * the arena table of contents.  The first time clump groups
+ * are accessed, we scan the entire arena table of contents
+ * (which might be 10s of megabytes), recording the data 
+ * offset of each clump group.
+ */
+
+/* 
+ * load clump info group information by scanning entire toc.
+ */
+static void
+loadcig(Arena *arena)
+{
+	u32int i, j, ncig, nci;
+	ArenaCIG *cig;
+	ClumpInfo *ci;
+	u64int offset;
+	int ms;
+
+	if(arena->cig || arena->ncig < 0)
+		return;
+
+//	fprint(2, "loadcig %s\n", arena->name);
+	
+	ncig = (arena->memstats.clumps+ArenaCIGSize-1) / ArenaCIGSize;
+	if(ncig == 0){
+		arena->cig = vtmalloc(1);
+		arena->ncig = 0;
+		return;
+	}
+
+	ms = msec();
+	cig = vtmalloc(ncig*sizeof cig[0]);
+	ci = vtmalloc(ArenaCIGSize*sizeof ci[0]);
+	offset = 0;
+	for(i=0; i<ncig; i++){
+		nci = readclumpinfos(arena, i*ArenaCIGSize, ci, ArenaCIGSize);
+		cig[i].offset = offset;
+		for(j=0; j<nci; j++)
+			offset += ClumpSize + ci[j].size;
+		if(nci < ArenaCIGSize){
+			if(i != ncig-1){
+				vtfree(ci);
+				vtfree(cig);
+				arena->ncig = -1;
+				fprint(2, "loadcig %s: got %ud cigs, expected %ud\n", arena->name, i+1, ncig);
+				goto out;
+			}
+		}
+	}
+	vtfree(ci);
+	
+	arena->ncig = ncig;
+	arena->cig = cig;
+
+out:
+	ms = msec() - ms;
+	addstat2(StatCigLoad, 1, StatCigLoadTime, ms);
+}
+
+/*
+ * convert arena address into arena group + data boundaries.
+ */
+int
+arenatog(Arena *arena, u64int addr, u64int *gstart, u64int *glimit, int *g)
+{
+	int r, l, m;
+
+	qlock(&arena->lock);
+	if(arena->cig == nil)
+		loadcig(arena);
+	if(arena->cig == nil || arena->ncig == 0){
+		qunlock(&arena->lock);
+		return -1;
+	}
+
+	l = 1;
+	r = arena->ncig - 1;
+	while(l <= r){
+		m = (r + l) / 2;
+		if(arena->cig[m].offset <= addr)
+			l = m + 1;
+		else
+			r = m - 1;
+	}
+	l--;
+
+	*g = l;
+	*gstart = arena->cig[l].offset;
+	if(l+1 < arena->ncig)
+		*glimit = arena->cig[l+1].offset;
+	else
+		*glimit = arena->memstats.used;
+	qunlock(&arena->lock);
+	return 0;
+}
+
+/*
+ * load the clump info for group g into the index entries.
+ */
+int
+asumload(Arena *arena, int g, IEntry *entries, int nentries)
+{
+	int i, base, limit;
+	u64int addr;
+	ClumpInfo ci;
+	IEntry *ie;
+
+	if(nentries < ArenaCIGSize){
+		fprint(2, "asking for too few entries\n");
+		return -1;
+	}
+	
+	qlock(&arena->lock);
+	if(arena->cig == nil)
+		loadcig(arena);
+	if(arena->cig == nil || arena->ncig == 0 || g >= arena->ncig){
+		qunlock(&arena->lock);
+		return -1;
+	}
+	
+	addr = 0;
+	base = g*ArenaCIGSize;
+	limit = base + ArenaCIGSize;
+	if(base > arena->memstats.clumps)
+		base = arena->memstats.clumps;
+	ie = entries;
+	for(i=base; i<limit; i++){
+		if(readclumpinfo(arena, i, &ci) < 0)
+			break;
+		if(ci.type != VtCorruptType){
+			scorecp(ie->score, ci.score);
+			ie->ia.type = ci.type;
+			ie->ia.size = ci.uncsize;
+			ie->ia.blocks = (ci.size + ClumpSize + (1<<ABlockLog) - 1) >> ABlockLog;
+			ie->ia.addr = addr;
+			ie++;
+		}
+		addr += ClumpSize + ci.size;
+	}
+	qunlock(&arena->lock);
+	return ie - entries;
+}