bcachefs: Fixes for replicas tracking

The continue statement in bch2_trans_mark_extent() was wrong - by
bailing out early, we'd be constructing the wrong replicas list to
update. Also, the assertion in update_replicas() was wrong - due to
rounding with compressed extents, it is possible for sectors to be 0
sometimes.

Also, change extent_to_replicas() in replicas.c to match the replicas
list we construct in buckets.c.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/buckets.c

@@ -520,7 +520,6 @@ static inline void update_replicas(struct bch_fs *c,
 	int idx = bch2_replicas_entry_idx(c, r);
 
 	BUG_ON(idx < 0);
-	BUG_ON(!sectors);
 
 	switch (r->data_type) {
 	case BCH_DATA_BTREE:
@@ -569,8 +568,12 @@ static inline void update_replicas_list(struct btree_trans *trans,
 {
 	struct replicas_delta_list *d;
 	struct replicas_delta *n;
-	unsigned b = replicas_entry_bytes(r) + 8;
+	unsigned b;
+
+	if (!sectors)
+		return;
 
+	b = replicas_entry_bytes(r) + 8;
 	d = replicas_deltas_realloc(trans, b);
 
 	n = (void *) d->d + d->used;
@@ -1029,7 +1032,7 @@ static int bch2_mark_extent(struct bch_fs *c, struct bkey_s_c k,
 					fs_usage, journal_seq, flags);
 
 		if (p.ptr.cached) {
-			if (disk_sectors && !stale)
+			if (!stale)
 				update_cached_sectors(c, fs_usage, p.ptr.dev,
 						      disk_sectors);
 		} else if (!p.ec_nr) {
@@ -1048,8 +1051,7 @@ static int bch2_mark_extent(struct bch_fs *c, struct bkey_s_c k,
 		}
 	}
 
-	if (dirty_sectors)
-		update_replicas(c, fs_usage, &r.e, dirty_sectors);
+	update_replicas(c, fs_usage, &r.e, dirty_sectors);
 
 	return 0;
 }
@@ -1561,12 +1563,6 @@ static int bch2_trans_mark_extent(struct btree_trans *trans,
 			? sectors
 			: ptr_disk_sectors_delta(p, offset, sectors, flags);
 
-		/*
-		 * can happen due to rounding with compressed extents:
-		 */
-		if (!disk_sectors)
-			continue;
-
 		ret = bch2_trans_mark_pointer(trans, p, disk_sectors,
 					      data_type);
 		if (ret < 0)
@@ -1575,7 +1571,7 @@ static int bch2_trans_mark_extent(struct btree_trans *trans,
 		stale = ret > 0;
 
 		if (p.ptr.cached) {
-			if (disk_sectors && !stale)
+			if (!stale)
 				update_cached_sectors_list(trans, p.ptr.dev,
 							   disk_sectors);
 		} else if (!p.ec_nr) {
@@ -1593,8 +1589,7 @@ static int bch2_trans_mark_extent(struct btree_trans *trans,
 		}
 	}
 
-	if (dirty_sectors)
-		update_replicas_list(trans, &r.e, dirty_sectors);
+	update_replicas_list(trans, &r.e, dirty_sectors);
 
 	return 0;
 }

fs/bcachefs/replicas.c

@@ -80,7 +80,7 @@ static void extent_to_replicas(struct bkey_s_c k,
 			continue;
 
 		if (p.ec_nr) {
-			r->nr_devs = 0;
+			r->nr_required = 0;
 			break;
 		}