bcachefs: Improve invalidate_one_bucket() error messages

Make sure to check for lru entries that point to buckets that don't
exist as well as buckets in the wrong state, and improve the error
message we print out.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/alloc_background.c

@@ -1751,37 +1751,38 @@ void bch2_do_discards(struct bch_fs *c)
 
 static int invalidate_one_bucket(struct btree_trans *trans,
 				 struct btree_iter *lru_iter,
-				 struct bpos bucket,
+				 struct bkey_s_c lru_k,
 				 s64 *nr_to_invalidate)
 {
 	struct bch_fs *c = trans->c;
 	struct btree_iter alloc_iter = { NULL };
-	struct bkey_i_alloc_v4 *a;
+	struct bkey_i_alloc_v4 *a = NULL;
 	struct printbuf buf = PRINTBUF;
+	struct bpos bucket = u64_to_bucket(lru_k.k->p.offset);
 	unsigned cached_sectors;
 	int ret = 0;
 
 	if (*nr_to_invalidate <= 0)
 		return 1;
 
+	if (!bch2_dev_bucket_exists(c, bucket)) {
+		prt_str(&buf, "lru entry points to invalid bucket");
+		goto err;
+	}
+
 	a = bch2_trans_start_alloc_update(trans, &alloc_iter, bucket);
 	ret = PTR_ERR_OR_ZERO(a);
 	if (ret)
 		goto out;
 
 	if (lru_pos_time(lru_iter->pos) != alloc_lru_idx(a->v)) {
-		prt_printf(&buf, "alloc key does not point back to lru entry when invalidating bucket:\n  ");
-		bch2_bpos_to_text(&buf, lru_iter->pos);
-		prt_printf(&buf, "\n  ");
-		bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(&a->k_i));
-
-		bch_err(c, "%s", buf.buf);
-		if (test_bit(BCH_FS_CHECK_LRUS_DONE, &c->flags)) {
-			bch2_inconsistent_error(c);
-			ret = -EINVAL;
-		}
+		prt_str(&buf, "alloc key does not point back to lru entry when invalidating bucket:");
+		goto err;
+	}
 
-		goto out;
+	if (a->v.data_type != BCH_DATA_cached) {
+		prt_str(&buf, "lru entry points to non cached bucket:");
+		goto err;
 	}
 
 	if (!a->v.cached_sectors)
@@ -1810,6 +1811,26 @@ static int invalidate_one_bucket(struct btree_trans *trans,
 	bch2_trans_iter_exit(trans, &alloc_iter);
 	printbuf_exit(&buf);
 	return ret;
+err:
+	prt_str(&buf, "\n  lru key: ");
+	bch2_bkey_val_to_text(&buf, c, lru_k);
+
+	prt_str(&buf, "\n  lru entry: ");
+	bch2_lru_pos_to_text(&buf, lru_iter->pos);
+
+	prt_str(&buf, "\n  alloc key: ");
+	if (!a)
+		bch2_bpos_to_text(&buf, bucket);
+	else
+		bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(&a->k_i));
+
+	bch_err(c, "%s", buf.buf);
+	if (test_bit(BCH_FS_CHECK_LRUS_DONE, &c->flags)) {
+		bch2_inconsistent_error(c);
+		ret = -EINVAL;
+	}
+
+	goto out;
 }
 
 static void bch2_do_invalidates_work(struct work_struct *work)
@@ -1832,9 +1853,7 @@ static void bch2_do_invalidates_work(struct work_struct *work)
 				lru_pos(ca->dev_idx, 0, 0),
 				lru_pos(ca->dev_idx, U64_MAX, LRU_TIME_MAX),
 				BTREE_ITER_INTENT, k,
-			invalidate_one_bucket(&trans, &iter,
-					      u64_to_bucket(k.k->p.offset),
-					      &nr_to_invalidate));
+			invalidate_one_bucket(&trans, &iter, k, &nr_to_invalidate));
 
 		if (ret < 0) {
 			percpu_ref_put(&ca->ref);

fs/bcachefs/lru.c

@@ -37,6 +37,15 @@ void bch2_lru_to_text(struct printbuf *out, struct bch_fs *c,
 	prt_printf(out, "idx %llu", le64_to_cpu(lru->idx));
 }
 
+void bch2_lru_pos_to_text(struct printbuf *out, struct bpos lru)
+{
+	prt_printf(out, "%llu:%llu -> %llu:%llu",
+		   lru_pos_id(lru),
+		   lru_pos_time(lru),
+		   u64_to_bucket(lru.offset).inode,
+		   u64_to_bucket(lru.offset).offset);
+}
+
 static int __bch2_lru_set(struct btree_trans *trans, u16 lru_id,
 			u64 dev_bucket, u64 time, unsigned key_type)
 {

fs/bcachefs/lru.h

@@ -25,6 +25,8 @@ static inline u64 lru_pos_time(struct bpos pos)
 int bch2_lru_invalid(const struct bch_fs *, struct bkey_s_c, unsigned, struct printbuf *);
 void bch2_lru_to_text(struct printbuf *, struct bch_fs *, struct bkey_s_c);
 
+void bch2_lru_pos_to_text(struct printbuf *, struct bpos);
+
 #define bch2_bkey_ops_lru ((struct bkey_ops) {	\
 	.key_invalid	= bch2_lru_invalid,	\
 	.val_to_text	= bch2_lru_to_text,	\