diff --git a/fs/bcachefs/alloc_background.h b/fs/bcachefs/alloc_background.h
index 2790e516383d..2bcc648081c3 100644
--- a/fs/bcachefs/alloc_background.h
+++ b/fs/bcachefs/alloc_background.h
@@ -21,8 +21,7 @@ static inline bool bch2_dev_bucket_exists(struct bch_fs *c, struct bpos pos)
 		return false;
 
 	ca = bch_dev_bkey_exists(c, pos.inode);
-	return pos.offset >= ca->mi.first_bucket &&
-		pos.offset < ca->mi.nbuckets;
+	return bucket_valid(ca, pos.offset);
 }
 
 static inline u64 bucket_to_u64(struct bpos bucket)
diff --git a/fs/bcachefs/bcachefs.h b/fs/bcachefs/bcachefs.h
index 6366a6a90944..3dad47533491 100644
--- a/fs/bcachefs/bcachefs.h
+++ b/fs/bcachefs/bcachefs.h
@@ -470,6 +470,7 @@ enum bch_time_stats {
 #include "quota_types.h"
 #include "rebalance_types.h"
 #include "replicas_types.h"
+#include "sb-members_types.h"
 #include "subvolume_types.h"
 #include "super_types.h"
 #include "thread_with_file_types.h"
diff --git a/fs/bcachefs/buckets.h b/fs/bcachefs/buckets.h
index a84e14468276..97b4bf8961e2 100644
--- a/fs/bcachefs/buckets.h
+++ b/fs/bcachefs/buckets.h
@@ -12,7 +12,7 @@
 #include "extents.h"
 #include "sb-members.h"
 
-static inline size_t sector_to_bucket(const struct bch_dev *ca, sector_t s)
+static inline u64 sector_to_bucket(const struct bch_dev *ca, sector_t s)
 {
 	return div_u64(s, ca->mi.bucket_size);
 }
@@ -30,12 +30,16 @@ static inline sector_t bucket_remainder(const struct bch_dev *ca, sector_t s)
 	return remainder;
 }
 
-static inline size_t sector_to_bucket_and_offset(const struct bch_dev *ca, sector_t s,
-						 u32 *offset)
+static inline u64 sector_to_bucket_and_offset(const struct bch_dev *ca, sector_t s, u32 *offset)
 {
 	return div_u64_rem(s, ca->mi.bucket_size, offset);
 }
 
+static inline bool bucket_valid(const struct bch_dev *ca, u64 b)
+{
+	return b - ca->mi.first_bucket < ca->mi.nbuckets_minus_first;
+}
+
 #define for_each_bucket(_b, _buckets)				\
 	for (_b = (_buckets)->b + (_buckets)->first_bucket;	\
 	     _b < (_buckets)->b + (_buckets)->nbuckets; _b++)
@@ -94,7 +98,7 @@ static inline struct bucket *gc_bucket(struct bch_dev *ca, size_t b)
 {
 	struct bucket_array *buckets = gc_bucket_array(ca);
 
-	BUG_ON(b < buckets->first_bucket || b >= buckets->nbuckets);
+	BUG_ON(!bucket_valid(ca, b));
 	return buckets->b + b;
 }
 
@@ -111,7 +115,7 @@ static inline u8 *bucket_gen(struct bch_dev *ca, size_t b)
 {
 	struct bucket_gens *gens = bucket_gens(ca);
 
-	BUG_ON(b < gens->first_bucket || b >= gens->nbuckets);
+	BUG_ON(!bucket_valid(ca, b));
 	return gens->b + b;
 }
 
diff --git a/fs/bcachefs/extents.c b/fs/bcachefs/extents.c
index 1a331e539204..e9db8f6d6bc1 100644
--- a/fs/bcachefs/extents.c
+++ b/fs/bcachefs/extents.c
@@ -998,9 +998,7 @@ void bch2_extent_ptr_to_text(struct printbuf *out, struct bch_fs *c, const struc
 			prt_str(out, " cached");
 		if (ptr->unwritten)
 			prt_str(out, " unwritten");
-		if (b >= ca->mi.first_bucket &&
-		    b <  ca->mi.nbuckets &&
-		    ptr_stale(ca, ptr))
+		if (bucket_valid(ca, b) && ptr_stale(ca, ptr))
 			prt_printf(out, " stale");
 	}
 }
diff --git a/fs/bcachefs/sb-members.h b/fs/bcachefs/sb-members.h
index 5bf27d30ca29..fa55b9666241 100644
--- a/fs/bcachefs/sb-members.h
+++ b/fs/bcachefs/sb-members.h
@@ -210,6 +210,8 @@ static inline struct bch_member_cpu bch2_mi_to_cpu(struct bch_member *mi)
 {
 	return (struct bch_member_cpu) {
 		.nbuckets	= le64_to_cpu(mi->nbuckets),
+		.nbuckets_minus_first = le64_to_cpu(mi->nbuckets) -
+			le16_to_cpu(mi->first_bucket),
 		.first_bucket	= le16_to_cpu(mi->first_bucket),
 		.bucket_size	= le16_to_cpu(mi->bucket_size),
 		.group		= BCH_MEMBER_GROUP(mi),
diff --git a/fs/bcachefs/sb-members_types.h b/fs/bcachefs/sb-members_types.h
new file mode 100644
index 000000000000..c0eda888fe39
--- /dev/null
+++ b/fs/bcachefs/sb-members_types.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BCACHEFS_SB_MEMBERS_TYPES_H
+#define _BCACHEFS_SB_MEMBERS_TYPES_H
+
+struct bch_member_cpu {
+	u64			nbuckets;	/* device size */
+	u64			nbuckets_minus_first;
+	u16			first_bucket;   /* index of first bucket used */
+	u16			bucket_size;	/* sectors */
+	u16			group;
+	u8			state;
+	u8			discard;
+	u8			data_allowed;
+	u8			durability;
+	u8			freespace_initialized;
+	u8			valid;
+	u8			btree_bitmap_shift;
+	u64			btree_allocated_bitmap;
+};
+
+#endif /* _BCACHEFS_SB_MEMBERS_H */
diff --git a/fs/bcachefs/super_types.h b/fs/bcachefs/super_types.h
index 11bcef170c2c..368a63d938cf 100644
--- a/fs/bcachefs/super_types.h
+++ b/fs/bcachefs/super_types.h
@@ -26,19 +26,4 @@ struct bch_devs_list {
 	u8			data[BCH_BKEY_PTRS_MAX];
 };
 
-struct bch_member_cpu {
-	u64			nbuckets;	/* device size */
-	u16			first_bucket;   /* index of first bucket used */
-	u16			bucket_size;	/* sectors */
-	u16			group;
-	u8			state;
-	u8			discard;
-	u8			data_allowed;
-	u8			durability;
-	u8			freespace_initialized;
-	u8			valid;
-	u8			btree_bitmap_shift;
-	u64			btree_allocated_bitmap;
-};
-
 #endif /* _BCACHEFS_SUPER_TYPES_H */