bcachefs: Drop empty accounting updates

Signed-off-by: Kent Overstreet <[email protected]>

Author: Kent Overstreet

fs/bcachefs/disk_accounting.c

@@ -111,6 +111,16 @@ int bch2_disk_accounting_mod(struct btree_trans *trans,
 			if (bpos_eq(a->k.p, pos)) {
 				BUG_ON(nr != bch2_accounting_counters(&a->k));
 				acc_u64s(a->v.d, d, nr);
+
+				if (bch2_accounting_key_is_zero(accounting_i_to_s_c(a))) {
+					unsigned offset = (u64 *) a -
+						(u64 *) btree_trans_subbuf_base(trans, &trans->accounting);
+
+					trans->accounting.u64s -= a->k.u64s;
+					memmove_u64s_down(a,
+							  bkey_next(&a->k_i),
+							  trans->accounting.u64s - offset);
+				}
 				return 0;
 			}
 #endif