diff --git a/fs/bcachefs/btree_gc.c b/fs/bcachefs/btree_gc.c
index 75ea243..c353fbb 100644
--- a/fs/bcachefs/btree_gc.c
+++ b/fs/bcachefs/btree_gc.c
@@ -482,6 +482,24 @@ static void bch2_gc_free(struct bch_fs *c)
 	c->usage[1] = NULL;
 }
 
+static void fs_usage_reset(struct bch_fs_usage *fs_usage)
+{
+	unsigned offset = offsetof(typeof(*fs_usage), s.gc_start);
+
+	memset((void *) fs_usage + offset, 0,
+	       sizeof(*fs_usage) - offset);
+}
+
+static void fs_usage_cpy(struct bch_fs_usage *dst,
+			 struct bch_fs_usage *src)
+{
+	unsigned offset = offsetof(typeof(*dst), s.gc_start);
+
+	memcpy((void *) dst + offset,
+	       (void *) src + offset,
+	       sizeof(*dst) - offset);
+}
+
 static void bch2_gc_done_nocheck(struct bch_fs *c)
 {
 	struct bch_dev *ca;
@@ -530,17 +548,12 @@ static void bch2_gc_done_nocheck(struct bch_fs *c)
 
 	{
 		struct bch_fs_usage src = __bch2_fs_usage_read(c, 1);
-		struct bch_fs_usage *p;
 
-		for_each_possible_cpu(cpu) {
-			p = per_cpu_ptr(c->usage[0], cpu);
-			memset(p, 0, offsetof(typeof(*p), online_reserved));
-		}
+		for_each_possible_cpu(cpu)
+			fs_usage_reset(per_cpu_ptr(c->usage[0], cpu));
 
 		preempt_disable();
-		memcpy(this_cpu_ptr(c->usage[0]),
-		       &src,
-		       offsetof(typeof(*p), online_reserved));
+		fs_usage_cpy(this_cpu_ptr(c->usage[0]), &src);
 		preempt_enable();
 	}
 
@@ -668,9 +681,14 @@ static void bch2_gc_done(struct bch_fs *c, bool initial)
 	{
 		struct bch_fs_usage dst = __bch2_fs_usage_read(c, 0);
 		struct bch_fs_usage src = __bch2_fs_usage_read(c, 1);
-		struct bch_fs_usage *p;
 		unsigned r, b;
 
+		copy_fs_field(s.hidden,		"hidden");
+		copy_fs_field(s.data,		"data");
+		copy_fs_field(s.cached,		"cached");
+		copy_fs_field(s.reserved,	"reserved");
+		copy_fs_field(s.nr_inodes,	"nr_inodes");
+
 		for (r = 0; r < BCH_REPLICAS_MAX; r++) {
 			for (b = 0; b < BCH_DATA_NR; b++)
 				copy_fs_field(replicas[r].data[b],
@@ -685,16 +703,12 @@ static void bch2_gc_done(struct bch_fs *c, bool initial)
 		for (b = 0; b < BCH_DATA_NR; b++)
 			copy_fs_field(buckets[b],
 				      "buckets[%s]", bch2_data_types[b]);
-		copy_fs_field(nr_inodes, "nr_inodes");
 
-		for_each_possible_cpu(cpu) {
-			p = per_cpu_ptr(c->usage[0], cpu);
-			memset(p, 0, offsetof(typeof(*p), online_reserved));
-		}
+		for_each_possible_cpu(cpu)
+			fs_usage_reset(per_cpu_ptr(c->usage[0], cpu));
 
 		preempt_disable();
-		p = this_cpu_ptr(c->usage[0]);
-		memcpy(p, &dst, offsetof(typeof(*p), online_reserved));
+		fs_usage_cpy(this_cpu_ptr(c->usage[0]), &dst);
 		preempt_enable();
 	}
 out:
diff --git a/fs/bcachefs/buckets.c b/fs/bcachefs/buckets.c
index c53d7a0..16aafe8 100644
--- a/fs/bcachefs/buckets.c
+++ b/fs/bcachefs/buckets.c
@@ -106,9 +106,9 @@ static void bch2_fs_stats_verify(struct bch_fs *c)
 			      bch_data_types[j],
 			      stats.buckets[j]);
 
-	if ((s64) stats.online_reserved < 0)
+	if ((s64) stats.s.online_reserved < 0)
 		panic("sectors_online_reserved underflow: %lli\n",
-		      stats.online_reserved);
+		      stats.s.online_reserved);
 }
 
 static void bch2_dev_stats_verify(struct bch_dev *ca)
@@ -228,38 +228,6 @@ struct bch_fs_usage bch2_fs_usage_read(struct bch_fs *c)
 	return bch2_usage_read_raw(c->usage[0]);
 }
 
-struct fs_usage_sum {
-	u64	hidden;
-	u64	data;
-	u64	cached;
-	u64	reserved;
-};
-
-static inline struct fs_usage_sum __fs_usage_sum(struct bch_fs_usage stats)
-{
-	struct fs_usage_sum sum = { 0 };
-	unsigned i;
-
-	/*
-	 * For superblock and journal we count bucket usage, not sector usage,
-	 * because any internal fragmentation should _not_ be counted as
-	 * free space:
-	 */
-	sum.hidden += stats.buckets[BCH_DATA_SB];
-	sum.hidden += stats.buckets[BCH_DATA_JOURNAL];
-
-	for (i = 0; i < ARRAY_SIZE(stats.replicas); i++) {
-		sum.data	+= stats.replicas[i].data[BCH_DATA_BTREE];
-		sum.data	+= stats.replicas[i].data[BCH_DATA_USER];
-		sum.data	+= stats.replicas[i].ec_data;
-		sum.cached	+= stats.replicas[i].data[BCH_DATA_CACHED];
-		sum.reserved	+= stats.replicas[i].persistent_reserved;
-	}
-
-	sum.reserved += stats.online_reserved;
-	return sum;
-}
-
 #define RESERVE_FACTOR	6
 
 static u64 reserve_factor(u64 r)
@@ -274,9 +242,10 @@ static u64 avail_factor(u64 r)
 
 static inline u64 __bch2_fs_sectors_used(struct bch_fs *c, struct bch_fs_usage fs_usage)
 {
-	struct fs_usage_sum sum = __fs_usage_sum(fs_usage);
-
-	return sum.hidden + sum.data + reserve_factor(sum.reserved);
+	return fs_usage.s.hidden +
+		fs_usage.s.data +
+		reserve_factor(fs_usage.s.reserved +
+			       fs_usage.s.online_reserved);
 }
 
 u64 bch2_fs_sectors_used(struct bch_fs *c, struct bch_fs_usage fs_usage)
@@ -287,13 +256,14 @@ u64 bch2_fs_sectors_used(struct bch_fs *c, struct bch_fs_usage fs_usage)
 struct bch_fs_usage_short
 bch2_fs_usage_read_short(struct bch_fs *c)
 {
-	struct bch_fs_usage usage = bch2_fs_usage_read(c);
-	struct fs_usage_sum sum = __fs_usage_sum(usage);
+	struct bch_fs_usage_summarized usage =
+		bch2_usage_read_raw(&c->usage[0]->s);
 	struct bch_fs_usage_short ret;
 
-	ret.capacity	= READ_ONCE(c->capacity) - sum.hidden;
-	ret.used	= min(ret.capacity, sum.data +
-			      reserve_factor(sum.reserved));
+	ret.capacity	= READ_ONCE(c->capacity) - usage.hidden;
+	ret.used	= min(ret.capacity, usage.data +
+			      reserve_factor(usage.reserved +
+					     usage.online_reserved));
 	ret.nr_inodes	= usage.nr_inodes;
 
 	return ret;
@@ -334,8 +304,7 @@ void bch2_fs_usage_apply(struct bch_fs *c,
 			 struct disk_reservation *disk_res,
 			 struct gc_pos gc_pos)
 {
-	struct fs_usage_sum sum = __fs_usage_sum(*fs_usage);
-	s64 added = sum.data + sum.reserved;
+	s64 added = fs_usage->s.data + fs_usage->s.reserved;
 	s64 should_not_have_added;
 
 	percpu_rwsem_assert_held(&c->mark_lock);
@@ -353,7 +322,7 @@ void bch2_fs_usage_apply(struct bch_fs *c,
 
 	if (added > 0) {
 		disk_res->sectors		-= added;
-		fs_usage->online_reserved	-= added;
+		fs_usage->s.online_reserved	-= added;
 	}
 
 	preempt_disable();
@@ -368,6 +337,18 @@ void bch2_fs_usage_apply(struct bch_fs *c,
 	memset(fs_usage, 0, sizeof(*fs_usage));
 }
 
+static inline void account_bucket(struct bch_fs_usage *fs_usage,
+				  struct bch_dev_usage *dev_usage,
+				  enum bch_data_type type,
+				  int nr, s64 size)
+{
+	if (type == BCH_DATA_SB || type == BCH_DATA_JOURNAL)
+		fs_usage->s.hidden	+= size;
+
+	fs_usage->buckets[type]		+= size;
+	dev_usage->buckets[type]	+= nr;
+}
+
 static void bch2_dev_usage_update(struct bch_fs *c, struct bch_dev *ca,
 				  struct bch_fs_usage *fs_usage,
 				  struct bucket_mark old, struct bucket_mark new,
@@ -386,15 +367,13 @@ static void bch2_dev_usage_update(struct bch_fs *c, struct bch_dev *ca,
 	preempt_disable();
 	dev_usage = this_cpu_ptr(ca->usage[gc]);
 
-	if (bucket_type(old)) {
-		fs_usage->buckets[bucket_type(old)] -= ca->mi.bucket_size;
-		dev_usage->buckets[bucket_type(old)]--;
-	}
+	if (bucket_type(old))
+		account_bucket(fs_usage, dev_usage, bucket_type(old),
+			       -1, -ca->mi.bucket_size);
 
-	if (bucket_type(new)) {
-		fs_usage->buckets[bucket_type(new)] += ca->mi.bucket_size;
-		dev_usage->buckets[bucket_type(new)]++;
-	}
+	if (bucket_type(new))
+		account_bucket(fs_usage, dev_usage, bucket_type(new),
+			       1, ca->mi.bucket_size);
 
 	dev_usage->buckets_alloc +=
 		(int) new.owned_by_allocator - (int) old.owned_by_allocator;
@@ -460,7 +439,8 @@ static void __bch2_invalidate_bucket(struct bch_fs *c, struct bch_dev *ca,
 		new.gen++;
 	}));
 
-	fs_usage->replicas[0].data[BCH_DATA_CACHED] -= old->cached_sectors;
+	fs_usage->replicas[0].data[BCH_DATA_CACHED]	-= old->cached_sectors;
+	fs_usage->s.cached				-= old->cached_sectors;
 }
 
 void bch2_invalidate_bucket(struct bch_fs *c, struct bch_dev *ca,
@@ -528,7 +508,10 @@ static void __bch2_mark_metadata_bucket(struct bch_fs *c, struct bch_dev *ca,
 		checked_add(new.dirty_sectors, sectors);
 	}));
 
-	fs_usage->replicas[0].data[type] += sectors;
+	if (type == BCH_DATA_BTREE ||
+	    type == BCH_DATA_USER)
+		fs_usage->s.data		+= sectors;
+	fs_usage->replicas[0].data[type]	+= sectors;
 }
 
 void bch2_mark_metadata_bucket(struct bch_fs *c, struct bch_dev *ca,
@@ -755,8 +738,13 @@ static int bch2_mark_extent(struct bch_fs *c, struct bkey_s_c k,
 	ec_redundancy	= clamp_t(unsigned,	ec_redundancy,
 				  1, ARRAY_SIZE(fs_usage->replicas));
 
+	fs_usage->s.cached					+= cached_sectors;
 	fs_usage->replicas[0].data[BCH_DATA_CACHED]		+= cached_sectors;
+
+	fs_usage->s.data					+= dirty_sectors;
 	fs_usage->replicas[replicas - 1].data[data_type]	+= dirty_sectors;
+
+	fs_usage->s.data					+= ec_sectors;
 	fs_usage->replicas[ec_redundancy - 1].ec_data		+= ec_sectors;
 
 	return 0;
@@ -866,9 +854,9 @@ static int __bch2_mark_key(struct bch_fs *c, struct bkey_s_c k,
 		break;
 	case KEY_TYPE_alloc:
 		if (inserting)
-			fs_usage->nr_inodes++;
+			fs_usage->s.nr_inodes++;
 		else
-			fs_usage->nr_inodes--;
+			fs_usage->s.nr_inodes--;
 		break;
 	case KEY_TYPE_reservation: {
 		unsigned replicas = bkey_s_c_to_reservation(k).v->nr_replicas;
@@ -877,7 +865,8 @@ static int __bch2_mark_key(struct bch_fs *c, struct bkey_s_c k,
 		replicas = clamp_t(unsigned, replicas,
 				   1, ARRAY_SIZE(fs_usage->replicas));
 
-		fs_usage->replicas[replicas - 1].persistent_reserved += sectors;
+		fs_usage->s.reserved					+= sectors;
+		fs_usage->replicas[replicas - 1].persistent_reserved	+= sectors;
 		break;
 	}
 	default:
@@ -1021,8 +1010,7 @@ static u64 bch2_recalc_sectors_available(struct bch_fs *c)
 void __bch2_disk_reservation_put(struct bch_fs *c, struct disk_reservation *res)
 {
 	percpu_down_read(&c->mark_lock);
-	this_cpu_sub(c->usage[0]->online_reserved,
-		     res->sectors);
+	this_cpu_sub(c->usage[0]->s.online_reserved, res->sectors);
 
 	bch2_fs_stats_verify(c);
 	percpu_up_read(&c->mark_lock);
@@ -1064,7 +1052,7 @@ int bch2_disk_reservation_add(struct bch_fs *c, struct disk_reservation *res,
 
 out:
 	pcpu->sectors_available		-= sectors;
-	this_cpu_add(c->usage[0]->online_reserved, sectors);
+	this_cpu_add(c->usage[0]->s.online_reserved, sectors);
 	res->sectors			+= sectors;
 
 	bch2_disk_reservations_verify(c, flags);
@@ -1098,7 +1086,7 @@ int bch2_disk_reservation_add(struct bch_fs *c, struct disk_reservation *res,
 	    (flags & BCH_DISK_RESERVATION_NOFAIL)) {
 		atomic64_set(&c->sectors_available,
 			     max_t(s64, 0, sectors_available - sectors));
-		this_cpu_add(c->usage[0]->online_reserved, sectors);
+		this_cpu_add(c->usage[0]->s.online_reserved, sectors);
 		res->sectors			+= sectors;
 		ret = 0;
 
diff --git a/fs/bcachefs/buckets_types.h b/fs/bcachefs/buckets_types.h
index f451a96..196f07f 100644
--- a/fs/bcachefs/buckets_types.h
+++ b/fs/bcachefs/buckets_types.h
@@ -63,6 +63,21 @@ struct bch_dev_usage {
 struct bch_fs_usage {
 	/* all fields are in units of 512 byte sectors: */
 
+	/* summarized: */
+	struct bch_fs_usage_summarized {
+		u64		online_reserved;
+
+		/* fields after online_reserved are cleared/recalculated by gc: */
+		u64		gc_start[0];
+
+		u64		hidden;
+		u64		data;
+		u64		cached;
+		u64		reserved;
+		u64		nr_inodes;
+	} s;
+
+	/* broken out: */
 	struct {
 		u64		data[BCH_DATA_NR];
 		u64		ec_data;
@@ -70,10 +85,6 @@ struct bch_fs_usage {
 	}			replicas[BCH_REPLICAS_MAX];
 
 	u64			buckets[BCH_DATA_NR];
-
-	u64			nr_inodes;
-
-	u64			online_reserved;
 };
 
 struct bch_fs_usage_short {
diff --git a/fs/bcachefs/chardev.c b/fs/bcachefs/chardev.c
index c11f8f4..7f79f02 100644
--- a/fs/bcachefs/chardev.c
+++ b/fs/bcachefs/chardev.c
@@ -398,7 +398,7 @@ static long bch2_ioctl_usage(struct bch_fs *c,
 		struct bch_ioctl_fs_usage dst = {
 			.capacity		= c->capacity,
 			.used			= bch2_fs_sectors_used(c, src),
-			.online_reserved	= src.online_reserved,
+			.online_reserved	= src.s.online_reserved,
 		};
 
 		for (i = 0; i < BCH_REPLICAS_MAX; i++) {
diff --git a/fs/bcachefs/sysfs.c b/fs/bcachefs/sysfs.c
index 7e46b25..a423159 100644
--- a/fs/bcachefs/sysfs.c
+++ b/fs/bcachefs/sysfs.c
@@ -259,7 +259,7 @@ static ssize_t show_fs_alloc_debug(struct bch_fs *c, char *buf)
 		       stats.buckets[type]);
 
 	pr_buf(&out, "online reserved:\t%llu\n",
-	       stats.online_reserved);
+	       stats.s.online_reserved);
 
 	return out.pos - buf;
 }