bcachefs: Improve checksum error messages

We're seeing checksum errors in the bch2_rechecksum_bio() path - give it
a better error message to help track this down.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/checksum.c

@@ -425,8 +425,17 @@ int bch2_rechecksum_bio(struct bch_fs *c, struct bio *bio,
 		merged = bch2_checksum_bio(c, crc_old.csum_type,
 				extent_nonce(version, crc_old), bio);
 
-	if (bch2_crc_cmp(merged, crc_old.csum))
+	if (bch2_crc_cmp(merged, crc_old.csum)) {
+		bch_err(c, "checksum error in bch2_rechecksum_bio() (memory corruption or bug?)\n"
+			"expected %0llx:%0llx got %0llx:%0llx (old type %s new type %s)",
+			crc_old.csum.hi,
+			crc_old.csum.lo,
+			merged.hi,
+			merged.lo,
+			bch2_csum_types[crc_old.csum_type],
+			bch2_csum_types[new_csum_type]);
 		return -EIO;
+	}
 
 	for (i = splits; i < splits + ARRAY_SIZE(splits); i++) {
 		if (i->crc)

fs/bcachefs/io.c

@@ -1186,8 +1186,7 @@ static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
 	*_dst = dst;
 	return more;
 csum_err:
-	bch_err(c, "error verifying existing checksum while "
-		"rewriting existing data (memory corruption?)");
+	bch_err(c, "error verifying existing checksum while rewriting existing data (memory corruption?)");
 	ret = -EIO;
 err:
 	if (to_wbio(dst)->bounce)
@@ -1977,9 +1976,9 @@ static void __bch2_read_endio(struct work_struct *work)
 	}
 
 	bch2_dev_inum_io_error(ca, rbio->read_pos.inode, (u64) rbio->bvec_iter.bi_sector,
-		"data checksum error: expected %0llx:%0llx got %0llx:%0llx (type %u)",
+		"data checksum error: expected %0llx:%0llx got %0llx:%0llx (type %s)",
 		rbio->pick.crc.csum.hi, rbio->pick.crc.csum.lo,
-		csum.hi, csum.lo, crc.csum_type);
+		csum.hi, csum.lo, bch2_csum_types[crc.csum_type]);
 	bch2_rbio_error(rbio, READ_RETRY_AVOID, BLK_STS_IOERR);
 	goto out;
 decompression_err: