X-Git-Url: http://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Ftdb2%2Ffree.c;h=658adec13bd4098859a9b7553994d0d0080d1391;hp=897d3cbe4627eaf69c9bf985a53608741b045fe5;hb=49475d68deecd0b31597ed6094229171d2699b11;hpb=323a9473c0aef80b8e18ef0c53529c8dfc29ec45

diff --git a/ccan/tdb2/free.c b/ccan/tdb2/free.c
index 897d3cbe..658adec1 100644
--- a/ccan/tdb2/free.c
+++ b/ccan/tdb2/free.c
@@ -59,32 +59,31 @@ tdb_off_t next_ftable(struct tdb_context *tdb, tdb_off_t ftable)
 	return tdb_read_off(tdb, ftable + offsetof(struct tdb_freetable,next));
 }
 
-int tdb_ftable_init(struct tdb_context *tdb)
+enum TDB_ERROR tdb_ftable_init(struct tdb_context *tdb)
 {
 	/* Use reservoir sampling algorithm to select a free list at random. */
 	unsigned int rnd, max = 0, count = 0;
 	tdb_off_t off;
 
-	tdb->ftable_off = off = first_ftable(tdb);
-	tdb->ftable = 0;
+	tdb->tdb2.ftable_off = off = first_ftable(tdb);
+	tdb->tdb2.ftable = 0;
 
 	while (off) {
 		if (TDB_OFF_IS_ERR(off)) {
-			tdb->ecode = off;
-			return -1;
+			return off;
 		}
 
 		rnd = random();
 		if (rnd >= max) {
-			tdb->ftable_off = off;
-			tdb->ftable = count;
+			tdb->tdb2.ftable_off = off;
+			tdb->tdb2.ftable = count;
 			max = rnd;
 		}
 
 		off = next_ftable(tdb, off);
 		count++;
 	}
-	return 0;
+	return TDB_SUCCESS;
 }
 
 /* Offset of a given bucket. */
@@ -104,170 +103,183 @@ static tdb_off_t find_free_head(struct tdb_context *tdb,
 				    bucket, TDB_FREE_BUCKETS);
 }
 
-/* Remove from free bucket. */
-static int remove_from_list(struct tdb_context *tdb,
-			    tdb_off_t b_off, tdb_off_t r_off,
-			    const struct tdb_free_record *r)
+static void check_list(struct tdb_context *tdb, tdb_off_t b_off)
 {
-	tdb_off_t off;
-	enum TDB_ERROR ecode;
-
-	/* Front of list? */
-	if (frec_prev(r) == 0) {
-		off = b_off;
-	} else {
-		off = frec_prev(r) + offsetof(struct tdb_free_record, next);
+#ifdef CCAN_TDB2_DEBUG
+	tdb_off_t off, prev = 0, first;
+	struct tdb_free_record r;
+
+	first = off = (tdb_read_off(tdb, b_off) & TDB_OFF_MASK);
+	while (off != 0) {
+		tdb_read_convert(tdb, off, &r, sizeof(r));
+		if (frec_magic(&r) != TDB_FREE_MAGIC)
+			abort();
+		if (prev && frec_prev(&r) != prev)
+			abort();
+		prev = off;
+		off = r.next;
 	}
 
-#ifdef CCAN_TDB2_DEBUG
-	if (tdb_read_off(tdb, off) != r_off) {
-		tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
-			 "remove_from_list: %llu bad prev in list %llu",
-			 (long long)r_off, (long long)b_off);
-		return -1;
+	if (first) {
+		tdb_read_convert(tdb, first, &r, sizeof(r));
+		if (frec_prev(&r) != prev)
+			abort();
 	}
 #endif
+}
 
-	/* r->prev->next = r->next */
-	ecode = tdb_write_off(tdb, off, r->next);
-	if (ecode != TDB_SUCCESS) {
-		tdb->ecode = ecode;
-		return -1;
+/* Remove from free bucket. */
+static enum TDB_ERROR remove_from_list(struct tdb_context *tdb,
+				       tdb_off_t b_off, tdb_off_t r_off,
+				       const struct tdb_free_record *r)
+{
+	tdb_off_t off, prev_next, head;
+	enum TDB_ERROR ecode;
+
+	/* Is this only element in list?  Zero out bucket, and we're done. */
+	if (frec_prev(r) == r_off)
+		return tdb_write_off(tdb, b_off, 0);
+
+	/* off = &r->prev->next */
+	off = frec_prev(r) + offsetof(struct tdb_free_record, next);
+
+	/* Get prev->next */
+	prev_next = tdb_read_off(tdb, off);
+	if (TDB_OFF_IS_ERR(prev_next))
+		return prev_next;
+
+	/* If prev->next == 0, we were head: update bucket to point to next. */
+	if (prev_next == 0) {
+		/* We must preserve upper bits. */
+		head = tdb_read_off(tdb, b_off);
+		if (TDB_OFF_IS_ERR(head))
+			return head;
+
+		if ((head & TDB_OFF_MASK) != r_off) {
+			return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
+					  "remove_from_list:"
+					  " %llu head %llu on list %llu",
+					  (long long)r_off,
+					  (long long)head,
+					  (long long)b_off);
+		}
+		head = ((head & ~TDB_OFF_MASK) | r->next);
+		ecode = tdb_write_off(tdb, b_off, head);
+		if (ecode != TDB_SUCCESS)
+			return ecode;
+	} else {
+		/* r->prev->next = r->next */
+		ecode = tdb_write_off(tdb, off, r->next);
+		if (ecode != TDB_SUCCESS)
+			return ecode;
 	}
 
-	if (r->next != 0) {
-		off = r->next + offsetof(struct tdb_free_record,magic_and_prev);
-		/* r->next->prev = r->prev */
+	/* If we were the tail, off = &head->prev. */
+	if (r->next == 0) {
+		head = tdb_read_off(tdb, b_off);
+		if (TDB_OFF_IS_ERR(head))
+			return head;
+		head &= TDB_OFF_MASK;
+		off = head + offsetof(struct tdb_free_record, magic_and_prev);
+	} else {
+		/* off = &r->next->prev */
+		off = r->next + offsetof(struct tdb_free_record,
+					 magic_and_prev);
+	}
 
 #ifdef CCAN_TDB2_DEBUG
-		if (tdb_read_off(tdb, off) & TDB_OFF_MASK != r_off) {
-			tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
-				   "remove_from_list: %llu bad list %llu",
-				   (long long)r_off, (long long)b_off);
-			return -1;
-		}
-#endif
-
-		ecode = tdb_write_off(tdb, off, r->magic_and_prev);
-		if (ecode != TDB_SUCCESS) {
-			tdb->ecode = ecode;
-			return -1;
-		}
+	/* *off == r */
+	if ((tdb_read_off(tdb, off) & TDB_OFF_MASK) != r_off) {
+		return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
+				  "remove_from_list:"
+				  " %llu bad prev in list %llu",
+				  (long long)r_off, (long long)b_off);
 	}
-	return 0;
+#endif
+	/* r->next->prev = r->prev */
+	return tdb_write_off(tdb, off, r->magic_and_prev);
 }
 
-/* Enqueue in this free bucket. */
-static int enqueue_in_free(struct tdb_context *tdb,
-			   tdb_off_t b_off,
-			   tdb_off_t off,
-			   tdb_len_t len)
+/* Enqueue in this free bucket: sets coalesce if we've added 128
+ * entries to it. */
+static enum TDB_ERROR enqueue_in_free(struct tdb_context *tdb,
+				      tdb_off_t b_off,
+				      tdb_off_t off,
+				      tdb_len_t len,
+				      bool *coalesce)
 {
 	struct tdb_free_record new;
 	enum TDB_ERROR ecode;
+	tdb_off_t prev, head;
 	uint64_t magic = (TDB_FREE_MAGIC << (64 - TDB_OFF_UPPER_STEAL));
 
+	head = tdb_read_off(tdb, b_off);
+	if (TDB_OFF_IS_ERR(head))
+		return head;
+
 	/* We only need to set ftable_and_len; rest is set in enqueue_in_free */
-	new.ftable_and_len = ((uint64_t)tdb->ftable << (64 - TDB_OFF_UPPER_STEAL))
+	new.ftable_and_len = ((uint64_t)tdb->tdb2.ftable << (64 - TDB_OFF_UPPER_STEAL))
 		| len;
-	/* prev = 0. */
-	new.magic_and_prev = magic;
 
 	/* new->next = head. */
-	new.next = tdb_read_off(tdb, b_off);
-	if (TDB_OFF_IS_ERR(new.next)) {
-		tdb->ecode = new.next;
-		return -1;
-	}
+	new.next = (head & TDB_OFF_MASK);
 
-	if (new.next) {
-#ifdef CCAN_TDB2_DEBUG
-		if (tdb_read_off(tdb,
-				 new.next + offsetof(struct tdb_free_record,
-						     magic_and_prev))
-		    != magic) {
-			tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
-				   "enqueue_in_free: %llu bad head"
-				   " prev %llu",
-				   (long long)new.next, (long long)b_off);
-			return -1;
+	/* First element?  Prev points to ourselves. */
+	if (!new.next) {
+		new.magic_and_prev = (magic | off);
+	} else {
+		/* new->prev = next->prev */
+		prev = tdb_read_off(tdb,
+				    new.next + offsetof(struct tdb_free_record,
+							magic_and_prev));
+		new.magic_and_prev = prev;
+		if (frec_magic(&new) != TDB_FREE_MAGIC) {
+			return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
+					  "enqueue_in_free: %llu bad head"
+					  " prev %llu",
+					  (long long)new.next,
+					  (long long)prev);
 		}
-#endif
 		/* next->prev = new. */
 		ecode = tdb_write_off(tdb, new.next
 				      + offsetof(struct tdb_free_record,
 						 magic_and_prev),
 				      off | magic);
 		if (ecode != TDB_SUCCESS) {
-			tdb->ecode = ecode;
-			return -1;
+			return ecode;
 		}
-	}
-	/* head = new */
-	ecode = tdb_write_off(tdb, b_off, off);
-	if (ecode != TDB_SUCCESS) {
-		tdb->ecode = ecode;
-		return -1;
-	}
 
-	ecode = tdb_write_convert(tdb, off, &new, sizeof(new));
-	if (ecode != TDB_SUCCESS) {
-		tdb->ecode = ecode;
-		return -1;
+#ifdef CCAN_TDB2_DEBUG
+		prev = tdb_read_off(tdb, frec_prev(&new)
+				    + offsetof(struct tdb_free_record, next));
+		if (prev != 0) {
+			return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
+					  "enqueue_in_free:"
+					  " %llu bad tail next ptr %llu",
+					  (long long)frec_prev(&new)
+					  + offsetof(struct tdb_free_record,
+						     next),
+					  (long long)prev);
+		}
+#endif
 	}
-	return 0;
-}
 
-/* List need not be locked. */
-int add_free_record(struct tdb_context *tdb,
-		    tdb_off_t off, tdb_len_t len_with_header)
-{
-	tdb_off_t b_off;
-	tdb_len_t len;
-	int ret;
-	enum TDB_ERROR ecode;
-
-	assert(len_with_header >= sizeof(struct tdb_free_record));
+	/* Update enqueue count, but don't set high bit: see TDB_OFF_IS_ERR */
+	if (*coalesce)
+		head += (1ULL << (64 - TDB_OFF_UPPER_STEAL));
+	head &= ~(TDB_OFF_MASK | (1ULL << 63));
+	head |= off;
 
-	len = len_with_header - sizeof(struct tdb_used_record);
-
-	b_off = bucket_off(tdb->ftable_off, size_to_bucket(len));
-	ecode = tdb_lock_free_bucket(tdb, b_off, TDB_LOCK_WAIT);
+	ecode = tdb_write_off(tdb, b_off, head);
 	if (ecode != TDB_SUCCESS) {
-		tdb->ecode = ecode;
-		return -1;
+		return ecode;
 	}
 
-	ret = enqueue_in_free(tdb, b_off, off, len);
-	tdb_unlock_free_bucket(tdb, b_off);
-	return ret;
-}
-
-static size_t adjust_size(size_t keylen, size_t datalen)
-{
-	size_t size = keylen + datalen;
-
-	if (size < TDB_MIN_DATA_LEN)
-		size = TDB_MIN_DATA_LEN;
-
-	/* Round to next uint64_t boundary. */
-	return (size + (sizeof(uint64_t) - 1ULL)) & ~(sizeof(uint64_t) - 1ULL);
-}
-
-/* If we have enough left over to be useful, split that off. */
-static size_t record_leftover(size_t keylen, size_t datalen,
-			      bool want_extra, size_t total_len)
-{
-	ssize_t leftover;
-
-	if (want_extra)
-		datalen += datalen / 2;
-	leftover = total_len - adjust_size(keylen, datalen);
+	/* It's time to coalesce if counter wrapped. */
+	if (*coalesce)
+		*coalesce = ((head & ~TDB_OFF_MASK) == 0);
 
-	if (leftover < (ssize_t)sizeof(struct tdb_free_record))
-		return 0;
-
-	return leftover;
+	return tdb_write_convert(tdb, off, &new, sizeof(new));
 }
 
 static tdb_off_t ftable_offset(struct tdb_context *tdb, unsigned int ftable)
@@ -275,13 +287,12 @@ static tdb_off_t ftable_offset(struct tdb_context *tdb, unsigned int ftable)
 	tdb_off_t off;
 	unsigned int i;
 
-	if (likely(tdb->ftable == ftable))
-		return tdb->ftable_off;
+	if (likely(tdb->tdb2.ftable == ftable))
+		return tdb->tdb2.ftable_off;
 
 	off = first_ftable(tdb);
 	for (i = 0; i < ftable; i++) {
 		if (TDB_OFF_IS_ERR(off)) {
-			tdb->ecode = off;
 			break;
 		}
 		off = next_ftable(tdb, off);
@@ -289,25 +300,28 @@ static tdb_off_t ftable_offset(struct tdb_context *tdb, unsigned int ftable)
 	return off;
 }
 
-/* Note: we unlock the current bucket if we coalesce or fail. */
-static int coalesce(struct tdb_context *tdb,
-		    tdb_off_t off, tdb_off_t b_off, tdb_len_t data_len)
+/* Note: we unlock the current bucket if fail (-ve), or coalesce (+ve) and
+ * need to blatt the *protect record (which is set to an error). */
+static tdb_len_t coalesce(struct tdb_context *tdb,
+			  tdb_off_t off, tdb_off_t b_off,
+			  tdb_len_t data_len,
+			  tdb_off_t *protect)
 {
 	tdb_off_t end;
 	struct tdb_free_record rec;
 	enum TDB_ERROR ecode;
 
-	add_stat(tdb, alloc_coalesce_tried, 1);
+	tdb->stats.alloc_coalesce_tried++;
 	end = off + sizeof(struct tdb_used_record) + data_len;
 
-	while (end < tdb->map_size) {
+	while (end < tdb->file->map_size) {
 		const struct tdb_free_record *r;
 		tdb_off_t nb_off;
 		unsigned ftable, bucket;
 
 		r = tdb_access_read(tdb, end, sizeof(*r), true);
 		if (TDB_PTR_IS_ERR(r)) {
-			tdb->ecode = TDB_PTR_ERR(r);
+			ecode = TDB_PTR_ERR(r);
 			goto err;
 		}
 
@@ -319,91 +333,310 @@ static int coalesce(struct tdb_context *tdb,
 
 		ftable = frec_ftable(r);
 		bucket = size_to_bucket(frec_len(r));
-		nb_off = bucket_off(ftable_offset(tdb, ftable), bucket);
+		nb_off = ftable_offset(tdb, ftable);
+		if (TDB_OFF_IS_ERR(nb_off)) {
+			tdb_access_release(tdb, r);
+			ecode = nb_off;
+			goto err;
+		}
+		nb_off = bucket_off(nb_off, bucket);
 		tdb_access_release(tdb, r);
 
 		/* We may be violating lock order here, so best effort. */
 		if (tdb_lock_free_bucket(tdb, nb_off, TDB_LOCK_NOWAIT)
 		    != TDB_SUCCESS) {
-			add_stat(tdb, alloc_coalesce_lockfail, 1);
+			tdb->stats.alloc_coalesce_lockfail++;
 			break;
 		}
 
 		/* Now we have lock, re-check. */
 		ecode = tdb_read_convert(tdb, end, &rec, sizeof(rec));
 		if (ecode != TDB_SUCCESS) {
-			tdb->ecode = ecode;
 			tdb_unlock_free_bucket(tdb, nb_off);
 			goto err;
 		}
 
 		if (unlikely(frec_magic(&rec) != TDB_FREE_MAGIC)) {
-			add_stat(tdb, alloc_coalesce_race, 1);
+			tdb->stats.alloc_coalesce_race++;
 			tdb_unlock_free_bucket(tdb, nb_off);
 			break;
 		}
 
 		if (unlikely(frec_ftable(&rec) != ftable)
 		    || unlikely(size_to_bucket(frec_len(&rec)) != bucket)) {
-			add_stat(tdb, alloc_coalesce_race, 1);
+			tdb->stats.alloc_coalesce_race++;
 			tdb_unlock_free_bucket(tdb, nb_off);
 			break;
 		}
 
-		if (remove_from_list(tdb, nb_off, end, &rec) == -1) {
+		/* Did we just mess up a record you were hoping to use? */
+		if (end == *protect) {
+			tdb->stats.alloc_coalesce_iterate_clash++;
+			*protect = TDB_ERR_NOEXIST;
+		}
+
+		ecode = remove_from_list(tdb, nb_off, end, &rec);
+		check_list(tdb, nb_off);
+		if (ecode != TDB_SUCCESS) {
 			tdb_unlock_free_bucket(tdb, nb_off);
 			goto err;
 		}
 
 		end += sizeof(struct tdb_used_record) + frec_len(&rec);
 		tdb_unlock_free_bucket(tdb, nb_off);
-		add_stat(tdb, alloc_coalesce_num_merged, 1);
+		tdb->stats.alloc_coalesce_num_merged++;
 	}
 
 	/* Didn't find any adjacent free? */
 	if (end == off + sizeof(struct tdb_used_record) + data_len)
 		return 0;
 
+	/* Before we expand, check this isn't one you wanted protected? */
+	if (off == *protect) {
+		*protect = TDB_ERR_EXISTS;
+		tdb->stats.alloc_coalesce_iterate_clash++;
+	}
+
 	/* OK, expand initial record */
 	ecode = tdb_read_convert(tdb, off, &rec, sizeof(rec));
 	if (ecode != TDB_SUCCESS) {
-		tdb->ecode = ecode;
 		goto err;
 	}
 
 	if (frec_len(&rec) != data_len) {
-		tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
-			   "coalesce: expected data len %zu not %zu",
-			   (size_t)data_len, (size_t)frec_len(&rec));
+		ecode = tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
+				   "coalesce: expected data len %zu not %zu",
+				   (size_t)data_len, (size_t)frec_len(&rec));
 		goto err;
 	}
 
-	if (remove_from_list(tdb, b_off, off, &rec) == -1)
-		goto err;
-
-	/* We have to drop this to avoid deadlocks, so make sure record
-	 * doesn't get coalesced by someone else! */
-	rec.ftable_and_len = (TDB_FTABLE_NONE << (64 - TDB_OFF_UPPER_STEAL))
-		| (end - off - sizeof(struct tdb_used_record));
-	ecode = tdb_write_off(tdb, off + offsetof(struct tdb_free_record,
-						  ftable_and_len),
-			      rec.ftable_and_len);
+	ecode = remove_from_list(tdb, b_off, off, &rec);
+	check_list(tdb, b_off);
 	if (ecode != TDB_SUCCESS) {
-		tdb->ecode = ecode;
 		goto err;
 	}
 
-	add_stat(tdb, alloc_coalesce_succeeded, 1);
-	tdb_unlock_free_bucket(tdb, b_off);
+	/* Try locking violation first.  We don't allow coalesce recursion! */
+	ecode = add_free_record(tdb, off, end - off, TDB_LOCK_NOWAIT, false);
+	if (ecode != TDB_SUCCESS) {
+		/* Need to drop lock.  Can't rely on anything stable. */
+		tdb->stats.alloc_coalesce_lockfail++;
+		*protect = TDB_ERR_CORRUPT;
+
+		/* We have to drop this to avoid deadlocks, so make sure record
+		 * doesn't get coalesced by someone else! */
+		rec.ftable_and_len = (TDB_FTABLE_NONE
+				      << (64 - TDB_OFF_UPPER_STEAL))
+			| (end - off - sizeof(struct tdb_used_record));
+		ecode = tdb_write_off(tdb,
+				      off + offsetof(struct tdb_free_record,
+						     ftable_and_len),
+				      rec.ftable_and_len);
+		if (ecode != TDB_SUCCESS) {
+			goto err;
+		}
+
+		tdb_unlock_free_bucket(tdb, b_off);
+
+		ecode = add_free_record(tdb, off, end - off, TDB_LOCK_WAIT,
+					false);
+		if (ecode != TDB_SUCCESS) {
+			return ecode;
+		}
+	} else if (TDB_OFF_IS_ERR(*protect)) {
+		/* For simplicity, we always drop lock if they can't continue */
+		tdb_unlock_free_bucket(tdb, b_off);
+	}
+	tdb->stats.alloc_coalesce_succeeded++;
 
-	if (add_free_record(tdb, off, end - off) == -1)
-		return -1;
-	return 1;
+	/* Return usable length. */
+	return end - off - sizeof(struct tdb_used_record);
 
 err:
 	/* To unify error paths, we *always* unlock bucket on error. */
 	tdb_unlock_free_bucket(tdb, b_off);
-	return -1;
+	return ecode;
+}
+
+/* List is locked: we unlock it. */
+static enum TDB_ERROR coalesce_list(struct tdb_context *tdb,
+				    tdb_off_t ftable_off,
+				    tdb_off_t b_off,
+				    unsigned int limit)
+{
+	enum TDB_ERROR ecode;
+	tdb_off_t off;
+
+	off = tdb_read_off(tdb, b_off);
+	if (TDB_OFF_IS_ERR(off)) {
+		ecode = off;
+		goto unlock_err;
+	}
+	/* A little bit of paranoia: counter should be 0. */
+	off &= TDB_OFF_MASK;
+
+	while (off && limit--) {
+		struct tdb_free_record rec;
+		tdb_len_t coal;
+		tdb_off_t next;
+
+		ecode = tdb_read_convert(tdb, off, &rec, sizeof(rec));
+		if (ecode != TDB_SUCCESS)
+			goto unlock_err;
+
+		next = rec.next;
+		coal = coalesce(tdb, off, b_off, frec_len(&rec), &next);
+		if (TDB_OFF_IS_ERR(coal)) {
+			/* This has already unlocked on error. */
+			return coal;
+		}
+		if (TDB_OFF_IS_ERR(next)) {
+			/* Coalescing had to unlock, so stop. */
+			return TDB_SUCCESS;
+		}
+		/* Keep going if we're doing well... */
+		limit += size_to_bucket(coal / 16 + TDB_MIN_DATA_LEN);
+		off = next;
+	}
+
+	/* Now, move those elements to the tail of the list so we get something
+	 * else next time. */
+	if (off) {
+		struct tdb_free_record oldhrec, newhrec, oldtrec, newtrec;
+		tdb_off_t oldhoff, oldtoff, newtoff;
+
+		/* The record we were up to is the new head. */
+		ecode = tdb_read_convert(tdb, off, &newhrec, sizeof(newhrec));
+		if (ecode != TDB_SUCCESS)
+			goto unlock_err;
+
+		/* Get the new tail. */
+		newtoff = frec_prev(&newhrec);
+		ecode = tdb_read_convert(tdb, newtoff, &newtrec,
+					 sizeof(newtrec));
+		if (ecode != TDB_SUCCESS)
+			goto unlock_err;
+
+		/* Get the old head. */
+		oldhoff = tdb_read_off(tdb, b_off);
+		if (TDB_OFF_IS_ERR(oldhoff)) {
+			ecode = oldhoff;
+			goto unlock_err;
+		}
+
+		/* This could happen if they all coalesced away. */
+		if (oldhoff == off)
+			goto out;
+
+		ecode = tdb_read_convert(tdb, oldhoff, &oldhrec,
+					 sizeof(oldhrec));
+		if (ecode != TDB_SUCCESS)
+			goto unlock_err;
+
+		/* Get the old tail. */
+		oldtoff = frec_prev(&oldhrec);
+		ecode = tdb_read_convert(tdb, oldtoff, &oldtrec,
+					 sizeof(oldtrec));
+		if (ecode != TDB_SUCCESS)
+			goto unlock_err;
+
+		/* Old tail's next points to old head. */
+		oldtrec.next = oldhoff;
+
+		/* Old head's prev points to old tail. */
+		oldhrec.magic_and_prev
+			= (TDB_FREE_MAGIC << (64 - TDB_OFF_UPPER_STEAL))
+			| oldtoff;
+
+		/* New tail's next is 0. */
+		newtrec.next = 0;
+
+		/* Write out the modified versions. */
+		ecode = tdb_write_convert(tdb, oldtoff, &oldtrec,
+					  sizeof(oldtrec));
+		if (ecode != TDB_SUCCESS)
+			goto unlock_err;
+
+		ecode = tdb_write_convert(tdb, oldhoff, &oldhrec,
+					  sizeof(oldhrec));
+		if (ecode != TDB_SUCCESS)
+			goto unlock_err;
+
+		ecode = tdb_write_convert(tdb, newtoff, &newtrec,
+					  sizeof(newtrec));
+		if (ecode != TDB_SUCCESS)
+			goto unlock_err;
+		
+		/* And finally link in new head. */
+		ecode = tdb_write_off(tdb, b_off, off);
+		if (ecode != TDB_SUCCESS)
+			goto unlock_err;
+	}
+out:
+	tdb_unlock_free_bucket(tdb, b_off);
+	return TDB_SUCCESS;
+
+unlock_err:
+	tdb_unlock_free_bucket(tdb, b_off);
+	return ecode;
+}
+
+/* List must not be locked if coalesce_ok is set. */
+enum TDB_ERROR add_free_record(struct tdb_context *tdb,
+			       tdb_off_t off, tdb_len_t len_with_header,
+			       enum tdb_lock_flags waitflag,
+			       bool coalesce)
+{
+	tdb_off_t b_off;
+	tdb_len_t len;
+	enum TDB_ERROR ecode;
+
+	assert(len_with_header >= sizeof(struct tdb_free_record));
+
+	len = len_with_header - sizeof(struct tdb_used_record);
+
+	b_off = bucket_off(tdb->tdb2.ftable_off, size_to_bucket(len));
+	ecode = tdb_lock_free_bucket(tdb, b_off, waitflag);
+	if (ecode != TDB_SUCCESS) {
+		return ecode;
+	}
+
+	ecode = enqueue_in_free(tdb, b_off, off, len, &coalesce);
+	check_list(tdb, b_off);
+
+	/* Coalescing unlocks free list. */
+	if (!ecode && coalesce)
+		ecode = coalesce_list(tdb, tdb->tdb2.ftable_off, b_off, 2);
+	else
+		tdb_unlock_free_bucket(tdb, b_off);
+	return ecode;
+}
+
+static size_t adjust_size(size_t keylen, size_t datalen)
+{
+	size_t size = keylen + datalen;
+
+	if (size < TDB_MIN_DATA_LEN)
+		size = TDB_MIN_DATA_LEN;
+
+	/* Round to next uint64_t boundary. */
+	return (size + (sizeof(uint64_t) - 1ULL)) & ~(sizeof(uint64_t) - 1ULL);
+}
+
+/* If we have enough left over to be useful, split that off. */
+static size_t record_leftover(size_t keylen, size_t datalen,
+			      bool want_extra, size_t total_len)
+{
+	ssize_t leftover;
+
+	if (want_extra)
+		datalen += datalen / 2;
+	leftover = total_len - adjust_size(keylen, datalen);
+
+	if (leftover < (ssize_t)sizeof(struct tdb_free_record))
+		return 0;
+
+	return leftover;
 }
 
 /* We need size bytes to put our key and data in. */
@@ -421,16 +654,14 @@ static tdb_off_t lock_and_alloc(struct tdb_context *tdb,
 	size_t size = adjust_size(keylen, datalen);
 	enum TDB_ERROR ecode;
 
-	add_stat(tdb, allocs, 1);
-again:
+	tdb->stats.allocs++;
 	b_off = bucket_off(ftable_off, bucket);
 
 	/* FIXME: Try non-blocking wait first, to measure contention. */
 	/* Lock this bucket. */
 	ecode = tdb_lock_free_bucket(tdb, b_off, TDB_LOCK_WAIT);
 	if (ecode != TDB_SUCCESS) {
-		tdb->ecode = ecode;
-		return TDB_OFF_ERR;
+		return ecode;
 	}
 
 	best.ftable_and_len = -1ULL;
@@ -446,9 +677,10 @@ again:
 	 * as we go. */
 	off = tdb_read_off(tdb, b_off);
 	if (TDB_OFF_IS_ERR(off)) {
-		tdb->ecode = off;
+		ecode = off;
 		goto unlock_err;
 	}
+	off &= TDB_OFF_MASK;
 
 	while (off) {
 		const struct tdb_free_record *r;
@@ -457,15 +689,17 @@ again:
 
 		r = tdb_access_read(tdb, off, sizeof(*r), true);
 		if (TDB_PTR_IS_ERR(r)) {
-			tdb->ecode = TDB_PTR_ERR(r);
+			ecode = TDB_PTR_ERR(r);
 			goto unlock_err;
 		}
 
 		if (frec_magic(r) != TDB_FREE_MAGIC) {
+			ecode = tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
+					   "lock_and_alloc:"
+					   " %llu non-free 0x%llx",
+					   (long long)off,
+					   (long long)r->magic_and_prev);
 			tdb_access_release(tdb, r);
-			tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
-				 "lock_and_alloc: %llu non-free 0x%llx",
-				 (long long)off, (long long)r->magic_and_prev);
 			goto unlock_err;
 		}
 
@@ -474,7 +708,7 @@ again:
 			best = *r;
 		}
 
-		if (frec_len(&best) < size * multiplier && best_off) {
+		if (frec_len(&best) <= size * multiplier && best_off) {
 			tdb_access_release(tdb, r);
 			break;
 		}
@@ -484,16 +718,6 @@ again:
 		next = r->next;
 		len = frec_len(r);
 		tdb_access_release(tdb, r);
-
-		/* Since we're going slow anyway, try coalescing here. */
-		switch (coalesce(tdb, off, b_off, len)) {
-		case -1:
-			/* This has already unlocked on error. */
-			return -1;
-		case 1:
-			/* This has unlocked list, restart. */
-			goto again;
-		}
 		off = next;
 	}
 
@@ -503,8 +727,11 @@ again:
 		size_t leftover;
 
 		/* We're happy with this size: take it. */
-		if (remove_from_list(tdb, b_off, best_off, &best) != 0)
+		ecode = remove_from_list(tdb, b_off, best_off, &best);
+		check_list(tdb, b_off);
+		if (ecode != TDB_SUCCESS) {
 			goto unlock_err;
+		}
 
 		leftover = record_leftover(keylen, datalen, want_extra,
 					   frec_len(&best));
@@ -512,25 +739,37 @@ again:
 		assert(keylen + datalen + leftover <= frec_len(&best));
 		/* We need to mark non-free before we drop lock, otherwise
 		 * coalesce() could try to merge it! */
-		if (set_header(tdb, &rec, magic, keylen, datalen,
-			       frec_len(&best) - leftover, hashlow) != 0)
+		ecode = set_header(tdb, &rec, magic, keylen, datalen,
+				   frec_len(&best) - leftover, hashlow);
+		if (ecode != TDB_SUCCESS) {
 			goto unlock_err;
+		}
 
 		ecode = tdb_write_convert(tdb, best_off, &rec, sizeof(rec));
 		if (ecode != TDB_SUCCESS) {
-			tdb->ecode = ecode;
 			goto unlock_err;
 		}
 
+		/* For futureproofing, we put a 0 in any unused space. */
+		if (rec_extra_padding(&rec)) {
+			ecode = tdb->tdb2.io->twrite(tdb, best_off + sizeof(rec)
+						     + keylen + datalen, "", 1);
+			if (ecode != TDB_SUCCESS) {
+				goto unlock_err;
+			}
+		}
+
 		/* Bucket of leftover will be <= current bucket, so nested
 		 * locking is allowed. */
 		if (leftover) {
-			add_stat(tdb, alloc_leftover, 1);
-			if (add_free_record(tdb,
-					    best_off + sizeof(rec)
-					    + frec_len(&best) - leftover,
-					    leftover))
-				best_off = TDB_OFF_ERR;
+			tdb->stats.alloc_leftover++;
+			ecode = add_free_record(tdb,
+						best_off + sizeof(rec)
+						+ frec_len(&best) - leftover,
+						leftover, TDB_LOCK_WAIT, false);
+			if (ecode != TDB_SUCCESS) {
+				best_off = ecode;
+			}
 		}
 		tdb_unlock_free_bucket(tdb, b_off);
 
@@ -542,10 +781,10 @@ again:
 
 unlock_err:
 	tdb_unlock_free_bucket(tdb, b_off);
-	return TDB_OFF_ERR;
+	return ecode;
 }
 
-/* Get a free block from current free list, or 0 if none. */
+/* Get a free block from current free list, or 0 if none, -ve on error. */
 static tdb_off_t get_free(struct tdb_context *tdb,
 			  size_t keylen, size_t datalen, bool want_extra,
 			  unsigned magic, unsigned hashlow)
@@ -561,9 +800,9 @@ static tdb_off_t get_free(struct tdb_context *tdb,
 	else
 		start_b = size_to_bucket(adjust_size(keylen, datalen));
 
-	ftable_off = tdb->ftable_off;
-	ftable = tdb->ftable;
-	while (!wrapped || ftable_off != tdb->ftable_off) {
+	ftable_off = tdb->tdb2.ftable_off;
+	ftable = tdb->tdb2.ftable;
+	while (!wrapped || ftable_off != tdb->tdb2.ftable_off) {
 		/* Start at exact size bucket, and search up... */
 		for (b = find_free_head(tdb, ftable_off, start_b);
 		     b < TDB_FREE_BUCKETS;
@@ -572,31 +811,29 @@ static tdb_off_t get_free(struct tdb_context *tdb,
 			off = lock_and_alloc(tdb, ftable_off,
 					     b, keylen, datalen, want_extra,
 					     magic, hashlow);
-			if (off == TDB_OFF_ERR)
-				return TDB_OFF_ERR;
+			if (TDB_OFF_IS_ERR(off))
+				return off;
 			if (off != 0) {
 				if (b == start_b)
-					add_stat(tdb, alloc_bucket_exact, 1);
+					tdb->stats.alloc_bucket_exact++;
 				if (b == TDB_FREE_BUCKETS - 1)
-					add_stat(tdb, alloc_bucket_max, 1);
+					tdb->stats.alloc_bucket_max++;
 				/* Worked?  Stay using this list. */
-				tdb->ftable_off = ftable_off;
-				tdb->ftable = ftable;
+				tdb->tdb2.ftable_off = ftable_off;
+				tdb->tdb2.ftable = ftable;
 				return off;
 			}
 			/* Didn't work.  Try next bucket. */
 		}
 
 		if (TDB_OFF_IS_ERR(b)) {
-			tdb->ecode = b;
-			return 0;
+			return b;
 		}
 
 		/* Hmm, try next table. */
 		ftable_off = next_ftable(tdb, ftable_off);
 		if (TDB_OFF_IS_ERR(ftable_off)) {
-			tdb->ecode = ftable_off;
-			return 0;
+			return ftable_off;
 		}
 		ftable++;
 
@@ -604,8 +841,7 @@ static tdb_off_t get_free(struct tdb_context *tdb,
 			wrapped = true;
 			ftable_off = first_ftable(tdb);
 			if (TDB_OFF_IS_ERR(ftable_off)) {
-				tdb->ecode = ftable_off;
-				return 0;
+				return ftable_off;
 			}
 			ftable = 0;
 		}
@@ -614,10 +850,10 @@ static tdb_off_t get_free(struct tdb_context *tdb,
 	return 0;
 }
 
-int set_header(struct tdb_context *tdb,
-	       struct tdb_used_record *rec,
-	       unsigned magic, uint64_t keylen, uint64_t datalen,
-	       uint64_t actuallen, unsigned hashlow)
+enum TDB_ERROR set_header(struct tdb_context *tdb,
+			  struct tdb_used_record *rec,
+			  unsigned magic, uint64_t keylen, uint64_t datalen,
+			  uint64_t actuallen, unsigned hashlow)
 {
 	uint64_t keybits = (fls64(keylen) + 1) / 2;
 
@@ -632,68 +868,79 @@ int set_header(struct tdb_context *tdb,
 	if (rec_key_length(rec) != keylen
 	    || rec_data_length(rec) != datalen
 	    || rec_extra_padding(rec) != actuallen - (keylen + datalen)) {
-		tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
-			 "Could not encode k=%llu,d=%llu,a=%llu",
-			 (long long)keylen, (long long)datalen,
-			 (long long)actuallen);
-		return -1;
+		return tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
+				  "Could not encode k=%llu,d=%llu,a=%llu",
+				  (long long)keylen, (long long)datalen,
+				  (long long)actuallen);
 	}
-	return 0;
+	return TDB_SUCCESS;
 }
 
 /* Expand the database. */
-static int tdb_expand(struct tdb_context *tdb, tdb_len_t size)
+static enum TDB_ERROR tdb_expand(struct tdb_context *tdb, tdb_len_t size)
 {
-	uint64_t old_size;
+	uint64_t old_size, rec_size, map_size;
 	tdb_len_t wanted;
 	enum TDB_ERROR ecode;
 
-	/* We need room for the record header too. */
-	wanted = sizeof(struct tdb_used_record) + size;
-
 	/* Need to hold a hash lock to expand DB: transactions rely on it. */
 	if (!(tdb->flags & TDB_NOLOCK)
-	    && !tdb->allrecord_lock.count && !tdb_has_hash_locks(tdb)) {
-		tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
-			   "tdb_expand: must hold lock during expand");
-		return -1;
+	    && !tdb->file->allrecord_lock.count && !tdb_has_hash_locks(tdb)) {
+		return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
+				  "tdb_expand: must hold lock during expand");
 	}
 
-	/* always make room for at least 100 more records, and at
-           least 25% more space. */
-	if (size * TDB_EXTENSION_FACTOR > tdb->map_size / 4)
-		wanted = size * TDB_EXTENSION_FACTOR;
-	else
-		wanted = tdb->map_size / 4;
-	wanted = adjust_size(0, wanted);
-
 	/* Only one person can expand file at a time. */
 	ecode = tdb_lock_expand(tdb, F_WRLCK);
 	if (ecode != TDB_SUCCESS) {
-		tdb->ecode = ecode;
-		return -1;
+		return ecode;
 	}
 
 	/* Someone else may have expanded the file, so retry. */
-	old_size = tdb->map_size;
-	tdb->methods->oob(tdb, tdb->map_size + 1, true);
-	if (tdb->map_size != old_size) {
+	old_size = tdb->file->map_size;
+	tdb->tdb2.io->oob(tdb, tdb->file->map_size + 1, true);
+	if (tdb->file->map_size != old_size) {
 		tdb_unlock_expand(tdb, F_WRLCK);
-		return 0;
+		return TDB_SUCCESS;
 	}
 
-	ecode = tdb->methods->expand_file(tdb, wanted);
+	/* limit size in order to avoid using up huge amounts of memory for
+	 * in memory tdbs if an oddball huge record creeps in */
+	if (size > 100 * 1024) {
+		rec_size = size * 2;
+	} else {
+		rec_size = size * 100;
+	}
+
+	/* always make room for at least rec_size more records, and at
+	   least 25% more space. if the DB is smaller than 100MiB,
+	   otherwise grow it by 10% only. */
+	if (old_size > 100 * 1024 * 1024) {
+		map_size = old_size / 10;
+	} else {
+		map_size = old_size / 4;
+	}
+
+	if (map_size > rec_size) {
+		wanted = map_size;
+	} else {
+		wanted = rec_size;
+	}
+
+	/* We need room for the record header too. */
+	wanted = adjust_size(0, sizeof(struct tdb_used_record) + wanted);
+
+	ecode = tdb->tdb2.io->expand_file(tdb, wanted);
 	if (ecode != TDB_SUCCESS) {
-		tdb->ecode = ecode;
 		tdb_unlock_expand(tdb, F_WRLCK);
-		return -1;
+		return ecode;
 	}
 
 	/* We need to drop this lock before adding free record. */
 	tdb_unlock_expand(tdb, F_WRLCK);
 
-	add_stat(tdb, expands, 1);
-	return add_free_record(tdb, old_size, wanted);
+	tdb->stats.expands++;
+	return add_free_record(tdb, old_size, wanted, TDB_LOCK_WAIT, true);
 }
 
 /* This won't fail: it will expand the database if it has to. */
@@ -703,15 +950,18 @@ tdb_off_t alloc(struct tdb_context *tdb, size_t keylen, size_t datalen,
 	tdb_off_t off;
 
 	/* We can't hold pointers during this: we could unmap! */
-	assert(!tdb->direct_access);
+	assert(!tdb->tdb2.direct_access);
 
 	for (;;) {
+		enum TDB_ERROR ecode;
 		off = get_free(tdb, keylen, datalen, growing, magic, hash);
 		if (likely(off != 0))
 			break;
 
-		if (tdb_expand(tdb, adjust_size(keylen, datalen)))
-			return TDB_OFF_ERR;
+		ecode = tdb_expand(tdb, adjust_size(keylen, datalen));
+		if (ecode != TDB_SUCCESS) {
+			return ecode;
+		}
 	}
 
 	return off;