ebiederm@xxxxxxxxxxxx (Eric W. Biederman) writes: > Jamie Lokier <jamie@xxxxxxxxxxxxx> writes: > >>> revoked_file_ops return 0 from reads (aka EOF). Tell poll the file is >>> always ready for I/O and return -EIO from all other operations. >> >> I think read should return -EIO too. If a program is reading from a >> /proc file (say), and the thing it's reading suddenly disappears, EOF >> gives the false impression that it's read to the end of formatted data >> from that file and it can process the data as if it's complete, which >> is wrong. I just thought about that some more and I am not convinced. In general the current return values from proc after an I/O operation are suspect. seek returns -EINVAL instead of -EIO. poll returns DEFAULT_POLLMASK (which doesn't set POLLERR). So I am not convinced that the existing proc return values on error are correct, and they are recent additions so the historical precedent is not especially large. EOF does give the impression that you have read all of the data from the /proc file, and that is in fact the case. There is no more data coming from that proc file. That the data is stale is well know. That the data is not atomic, anything that spans more than a single read is not atomic. So I don't see what returning EIO adds to the equation. Perhaps that your fragile user space string parser may break? EOF gives a clear indication the application should stop reading the data, because there is no more. EIO only says that the was a problem. I don't know of anything that depends on the rmmod behavior either way. But if we can get away with it I would like to use something that is generally useful instead of something that only makes sense in the context of proc. Eric -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
