bcachefs: Ensure we don't exceed encoded_extent_max

The write path may (rarely) see an encoded (checksummed) extent that
exceeds encoded_extent_max - this can happen when we're moving an
existing extent that was not checksummed, but was given a checksum by
bch2_write_rechecksum().
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/io_write.c

@@ -816,6 +816,7 @@ static enum prep_encoded_ret {
 
 	/* Can we just write the entire extent as is? */
 	if (op->crc.uncompressed_size == op->crc.live_size &&
+	    op->crc.uncompressed_size <= c->opts.encoded_extent_max >> 9 &&
 	    op->crc.compressed_size <= wp->sectors_free &&
 	    (op->crc.compression_type == bch2_compression_opt_to_type(op->compression_opt) ||
 	     op->incompressible)) {