diff --git a/libbcachefs/alloc_background.c b/libbcachefs/alloc_background.c
index 990701a6..e252a039 100644
--- a/libbcachefs/alloc_background.c
+++ b/libbcachefs/alloc_background.c
@@ -152,6 +152,7 @@ void bch2_alloc_pack(struct bkey_i_alloc *dst,
 {
 	unsigned idx = 0;
 	void *d = dst->v.data;
+	unsigned bytes;
 
 	dst->v.fields	= 0;
 	dst->v.gen	= src.gen;
@@ -160,7 +161,9 @@ void bch2_alloc_pack(struct bkey_i_alloc *dst,
 	BCH_ALLOC_FIELDS()
 #undef  x
 
-	set_bkey_val_bytes(&dst->k, (void *) d - (void *) &dst->v);
+	bytes = (void *) d - (void *) &dst->v;
+	set_bkey_val_bytes(&dst->k, bytes);
+	memset_u64s_tail(&dst->v, 0, bytes);
 }
 
 static unsigned bch_alloc_val_u64s(const struct bch_alloc *a)
diff --git a/libbcachefs/btree_cache.c b/libbcachefs/btree_cache.c
index 41694951..2d8f6379 100644
--- a/libbcachefs/btree_cache.c
+++ b/libbcachefs/btree_cache.c
@@ -83,6 +83,9 @@ static void btree_node_data_alloc(struct bch_fs *c, struct btree *b, gfp_t gfp)
 	if (bch2_btree_keys_alloc(b, btree_page_order(c), gfp))
 		goto err;
 
+	memset(&b->data->csum, 0, sizeof b->data->csum);
+	b->data->flags = 0;
+
 	bc->used++;
 	list_move(&b->list, &bc->freeable);
 	return;
diff --git a/libbcachefs/inode.c b/libbcachefs/inode.c
index e953b78f..59653b97 100644
--- a/libbcachefs/inode.c
+++ b/libbcachefs/inode.c
@@ -95,6 +95,7 @@ void bch2_inode_pack(struct bkey_inode_buf *packed,
 	u8 *end = (void *) &packed[1];
 	u8 *last_nonzero_field = out;
 	unsigned nr_fields = 0, last_nonzero_fieldnr = 0;
+	unsigned bytes;
 
 	bkey_inode_init(&packed->inode.k_i);
 	packed->inode.k.p.inode		= inode->bi_inum;
@@ -117,10 +118,9 @@ void bch2_inode_pack(struct bkey_inode_buf *packed,
 	out = last_nonzero_field;
 	nr_fields = last_nonzero_fieldnr;
 
-	set_bkey_val_bytes(&packed->inode.k, out - (u8 *) &packed->inode.v);
-	memset(out, 0,
-	       (u8 *) &packed->inode.v +
-	       bkey_val_bytes(&packed->inode.k) - out);
+	bytes = out - (u8 *) &packed->inode.v;
+	set_bkey_val_bytes(&packed->inode.k, bytes);
+	memset_u64s_tail(&packed->inode.v, 0, bytes);
 
 	SET_INODE_NR_FIELDS(&packed->inode.v, nr_fields);
 
diff --git a/libbcachefs/super-io.c b/libbcachefs/super-io.c
index 550a140d..b36cfdf0 100644
--- a/libbcachefs/super-io.c
+++ b/libbcachefs/super-io.c
@@ -949,6 +949,25 @@ int bch2_fs_mark_dirty(struct bch_fs *c)
 	return ret;
 }
 
+static void
+entry_init_u64s(struct jset_entry *entry, unsigned u64s)
+{
+	memset(entry, 0, u64s * sizeof(u64));
+
+	/*
+	 * The u64s field counts from the start of data, ignoring the shared
+	 * fields.
+	 */
+	entry->u64s = u64s - 1;
+}
+
+static void
+entry_init_size(struct jset_entry *entry, size_t size)
+{
+	unsigned u64s = DIV_ROUND_UP(size, sizeof(u64));
+	entry_init_u64s(entry, u64s);
+}
+
 struct jset_entry *
 bch2_journal_super_entries_add_common(struct bch_fs *c,
 				      struct jset_entry *entry,
@@ -963,7 +982,7 @@ bch2_journal_super_entries_add_common(struct bch_fs *c,
 	     r < c->btree_roots + BTREE_ID_NR;
 	     r++)
 		if (r->alive) {
-			entry->u64s	= r->key.u64s;
+			entry_init_u64s(entry, r->key.u64s + 1);
 			entry->btree_id	= r - c->btree_roots;
 			entry->level	= r->level;
 			entry->type	= BCH_JSET_ENTRY_btree_root;
@@ -988,8 +1007,7 @@ bch2_journal_super_entries_add_common(struct bch_fs *c,
 		struct jset_entry_usage *u =
 			container_of(entry, struct jset_entry_usage, entry);
 
-		memset(u, 0, sizeof(*u));
-		u->entry.u64s	= DIV_ROUND_UP(sizeof(*u), sizeof(u64)) - 1;
+		entry_init_size(entry, sizeof(*u));
 		u->entry.type	= BCH_JSET_ENTRY_usage;
 		u->entry.btree_id = FS_USAGE_INODES;
 		u->v		= cpu_to_le64(c->usage_base->nr_inodes);
@@ -1001,8 +1019,7 @@ bch2_journal_super_entries_add_common(struct bch_fs *c,
 		struct jset_entry_usage *u =
 			container_of(entry, struct jset_entry_usage, entry);
 
-		memset(u, 0, sizeof(*u));
-		u->entry.u64s	= DIV_ROUND_UP(sizeof(*u), sizeof(u64)) - 1;
+		entry_init_size(entry, sizeof(*u));
 		u->entry.type	= BCH_JSET_ENTRY_usage;
 		u->entry.btree_id = FS_USAGE_KEY_VERSION;
 		u->v		= cpu_to_le64(atomic64_read(&c->key_version));
@@ -1014,8 +1031,7 @@ bch2_journal_super_entries_add_common(struct bch_fs *c,
 		struct jset_entry_usage *u =
 			container_of(entry, struct jset_entry_usage, entry);
 
-		memset(u, 0, sizeof(*u));
-		u->entry.u64s	= DIV_ROUND_UP(sizeof(*u), sizeof(u64)) - 1;
+		entry_init_size(entry, sizeof(*u));
 		u->entry.type	= BCH_JSET_ENTRY_usage;
 		u->entry.btree_id = FS_USAGE_RESERVED;
 		u->entry.level	= i;
@@ -1030,10 +1046,7 @@ bch2_journal_super_entries_add_common(struct bch_fs *c,
 		struct jset_entry_data_usage *u =
 			container_of(entry, struct jset_entry_data_usage, entry);
 
-		int u64s = DIV_ROUND_UP(sizeof(*u) + e->nr_devs,
-					sizeof(u64)) - 1;
-		memset(u, 0, u64s * sizeof(u64));
-		u->entry.u64s	= u64s;
+		entry_init_size(entry, sizeof(*u) + e->nr_devs);
 		u->entry.type	= BCH_JSET_ENTRY_data_usage;
 		u->v		= cpu_to_le64(c->usage_base->replicas[i]);
 		memcpy(&u->r, e, replicas_entry_bytes(e));
diff --git a/libbcachefs/util.h b/libbcachefs/util.h
index fa3a9914..05027761 100644
--- a/libbcachefs/util.h
+++ b/libbcachefs/util.h
@@ -628,6 +628,14 @@ static inline void memmove_u64s(void *dst, const void *src,
 		__memmove_u64s_up(dst, src, u64s);
 }
 
+/* Set the last few bytes up to a u64 boundary given an offset into a buffer. */
+static inline void memset_u64s_tail(void *s, int c, unsigned bytes)
+{
+	unsigned rem = round_up(bytes, sizeof(u64)) - bytes;
+
+	memset(s + bytes, c, rem);
+}
+
 void sort_cmp_size(void *base, size_t num, size_t size,
 	  int (*cmp_func)(const void *, const void *, size_t),
 	  void (*swap_func)(void *, void *, size_t));