bcachefs: Add a persistent counter for bucket invalidation

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/alloc_background.c

@@ -1173,11 +1173,16 @@ static void bch2_do_invalidates_work(struct work_struct *work)
 		s64 nr_to_invalidate =
 			should_invalidate_buckets(ca, bch2_dev_usage_read(ca));
 
-		while (!ret && nr_to_invalidate-- >= 0)
+		while (nr_to_invalidate-- >= 0) {
 			ret = __bch2_trans_do(&trans, NULL, NULL,
 					      BTREE_INSERT_USE_RESERVE|
 					      BTREE_INSERT_NOFAIL,
 					invalidate_one_bucket(&trans, ca));
+			if (ret)
+				break;
+
+			this_cpu_inc(c->counters[BCH_COUNTER_bucket_invalidate]);
+		}
 	}
 
 	bch2_trans_exit(&trans);

fs/bcachefs/bcachefs_format.h

@@ -1326,10 +1326,11 @@ struct bch_sb_field_disk_groups {
 
 /* BCH_SB_FIELD_counters */
 
-#define BCH_PERSISTENT_COUNTERS()	\
-	x(io_read,  0)			\
-	x(io_write, 1)			\
-	x(io_move,  2)
+#define BCH_PERSISTENT_COUNTERS()			\
+	x(io_read,		0)			\
+	x(io_write,		1)			\
+	x(io_move,		2)			\
+	x(bucket_invalidate,	3)
 
 enum bch_persistent_counters {
 #define x(t, n, ...) BCH_COUNTER_##t,