bcachefs: bkey_format helper improvements

 - add a to_text() method for bkey_format

 - convert bch2_bkey_format_validate() to modern error message style,
   where we pass a printbuf for the error string instead of returning a
   static string
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bkey.c

@@ -608,12 +608,15 @@ struct bkey_format bch2_bkey_format_done(struct bkey_format_state *s)
 	return ret;
 }
 
-const char *bch2_bkey_format_validate(struct bkey_format *f)
+int bch2_bkey_format_validate(struct bkey_format *f, struct printbuf *err)
 {
 	unsigned i, bits = KEY_PACKED_BITS_START;
 
-	if (f->nr_fields != BKEY_NR_FIELDS)
-		return "incorrect number of fields";
+	if (f->nr_fields != BKEY_NR_FIELDS) {
+		prt_printf(err, "incorrect number of fields: got %u, should be %u",
+			   f->nr_fields, BKEY_NR_FIELDS);
+		return -BCH_ERR_invalid;
+	}
 
 	/*
 	 * Verify that the packed format can't represent fields larger than the
@@ -628,16 +631,35 @@ const char *bch2_bkey_format_validate(struct bkey_format *f)
 		u64 field_offset = le64_to_cpu(f->field_offset[i]);
 
 		if (packed_max + field_offset < packed_max ||
-		    packed_max + field_offset > unpacked_max)
-			return "field too large";
+		    packed_max + field_offset > unpacked_max) {
+			prt_printf(err, "field %u too large: %llu + %llu > %llu",
+				   i, packed_max, field_offset, unpacked_max);
+			return -BCH_ERR_invalid;
+		}
 
 		bits += f->bits_per_field[i];
 	}
 
-	if (f->key_u64s != DIV_ROUND_UP(bits, 64))
-		return "incorrect key_u64s";
+	if (f->key_u64s != DIV_ROUND_UP(bits, 64)) {
+		prt_printf(err, "incorrect key_u64s: got %u, should be %u",
+			   f->key_u64s, DIV_ROUND_UP(bits, 64));
+		return -BCH_ERR_invalid;
+	}
+
+	return 0;
+}
 
-	return NULL;
+void bch2_bkey_format_to_text(struct printbuf *out, const struct bkey_format *f)
+{
+	prt_printf(out, "u64s %u fields ", f->key_u64s);
+
+	for (unsigned i = 0; i < ARRAY_SIZE(f->bits_per_field); i++) {
+		if (i)
+			prt_str(out, ", ");
+		prt_printf(out, "%u:%llu",
+			   f->bits_per_field[i],
+			   le64_to_cpu(f->field_offset[i]));
+	}
 }
 
 /*

fs/bcachefs/bkey.h

@@ -769,6 +769,7 @@ static inline void bch2_bkey_format_add_key(struct bkey_format_state *s, const s
 
 void bch2_bkey_format_add_pos(struct bkey_format_state *, struct bpos);
 struct bkey_format bch2_bkey_format_done(struct bkey_format_state *);
-const char *bch2_bkey_format_validate(struct bkey_format *);
+int bch2_bkey_format_validate(struct bkey_format *, struct printbuf *);
+void bch2_bkey_format_to_text(struct printbuf *, const struct bkey_format *);
 
 #endif /* _BCACHEFS_BKEY_H */

fs/bcachefs/btree_cache.c

@@ -1165,7 +1165,6 @@ void bch2_btree_node_evict(struct btree_trans *trans, const struct bkey_i *k)
 void bch2_btree_node_to_text(struct printbuf *out, struct bch_fs *c,
 			     const struct btree *b)
 {
-	const struct bkey_format *f = &b->format;
 	struct bset_stats stats;
 
 	memset(&stats, 0, sizeof(stats));
@@ -1179,9 +1178,13 @@ void bch2_btree_node_to_text(struct printbuf *out, struct bch_fs *c,
 	prt_printf(out, ":\n"
 	       "    ptrs: ");
 	bch2_val_to_text(out, c, bkey_i_to_s_c(&b->key));
+	prt_newline(out);
 
-	prt_printf(out, "\n"
-	       "    format: u64s %u fields %u %u %u %u %u\n"
+	prt_printf(out,
+	       "    format: ");
+	bch2_bkey_format_to_text(out, &b->format);
+
+	prt_printf(out,
 	       "    unpack fn len: %u\n"
 	       "    bytes used %zu/%zu (%zu%% full)\n"
 	       "    sib u64s: %u, %u (merge threshold %u)\n"
@@ -1189,12 +1192,6 @@ void bch2_btree_node_to_text(struct printbuf *out, struct bch_fs *c,
 	       "    nr unpacked keys %u\n"
 	       "    floats %zu\n"
 	       "    failed unpacked %zu\n",
-	       f->key_u64s,
-	       f->bits_per_field[0],
-	       f->bits_per_field[1],
-	       f->bits_per_field[2],
-	       f->bits_per_field[3],
-	       f->bits_per_field[4],
 	       b->unpack_fn_len,
 	       b->nr.live_u64s * sizeof(u64),
 	       btree_bytes(c) - sizeof(struct btree_node),

fs/bcachefs/btree_io.c

@@ -694,7 +694,6 @@ static int validate_bset(struct bch_fs *c, struct bch_dev *ca,
 			 int write, bool have_retry, bool *saw_error)
 {
 	unsigned version = le16_to_cpu(i->version);
-	const char *err;
 	struct printbuf buf1 = PRINTBUF;
 	struct printbuf buf2 = PRINTBUF;
 	int ret = 0;
@@ -802,10 +801,12 @@ static int validate_bset(struct bch_fs *c, struct bch_dev *ca,
 			compat_btree_node(b->c.level, b->c.btree_id, version,
 					  BSET_BIG_ENDIAN(i), write, bn);
 
-		err = bch2_bkey_format_validate(&bn->format);
-		btree_err_on(err,
+		btree_err_on(bch2_bkey_format_validate(&bn->format, &buf1),
 			     BTREE_ERR_BAD_NODE, c, ca, b, i,
-			     "invalid bkey format: %s", err);
+			     "invalid bkey format: %s\n  %s", buf1.buf,
+			     (printbuf_reset(&buf2),
+			      bch2_bkey_format_to_text(&buf2, &bn->format), buf2.buf));
+		printbuf_reset(&buf1);
 
 		compat_bformat(b->c.level, b->c.btree_id, version,
 			       BSET_BIG_ENDIAN(i), write,