vboxfs EPROTO error during file read

[Brian Litzinger]

I recently attemped to use vboxsf/vboxfs to make an Ubuntu 8.04 host filesystem available in an Ubuntu 8.04 guest instance.

All worked fine initially. A relatively simple application in the guest reads and writes files into a folder in the shared directory.

Every once in a while the read() system call returns EPROTO. However, simply repeating the open/read/close works.

It was failing about 1% of the time.

I mounted the filesystem via NFS rather than vboxfs and the operations work 100% 24 hours per day for days on end.

The operations also work days on end if the files are read/written to the filesystem inside the guest.

I was unable to find anything in the log files at the time of the failed read calls.

[Frank Mehnert]

Please reopen if this is still an issue with VBox 3.2.0

[eyal]

I consistently encounter this problem on a windows host with linux guest (guest additions 4.1.6 on a Suse Linux guest). The problem is with reading a file that was opened prior to saving machine state (and restoring it later).

In other words, to reproduce you need to follow this sequence:

1. open() a file on a share (guest accessing the windows host)
2. Save machine state
3. Restore machine state
4. read() or pread() from the file descriptor opened in 1.

Result - read() fails and errno is EPROTO