@ncw i m hurry to convey that we encountered error while writing files with enabled kernel space read ahead (-o FileInfoTimeout=-1) for rclone mounted disk. I think it make sense for hurry as you noted that you would make kernel read ahead enabled by default in next rclone release but i need some time to prepare complete case description.
In simple, python is known to be affected when copying files to virtual file system with something like this:
with open(physical_path, 'rb') as source:
with open(rclone_path, 'wb') as dest:
while True:
buf = source.read(1024*1024)
if not buf:
break
dest.write(buf)
It raises OSError: [Errno 9] Bad file descriptor at some point.
System copy seems to be not affected with this issue.