2.3 SMP overlapping writes and NFS

Jamie Lokier (lkd@tantalophile.demon.co.uk)
Thu, 5 Aug 1999 05:27:20 +0200

If two processes write to an overlapping region of a file at the same
time, current 2.3 SMP kernels may mix the data from the two writes.
This is a consequence of the 2.3 SMP scalability changes, am I right?

I just spotted this in the NFSv2 spec (rfc1094)

Writes "data" beginning "offset" bytes from the beginning of "file".
The first byte of the file is at offset zero. If the reply "status"
is NFS_OK, then the reply "attributes" contains the attributes of the
file after the write has completed. The write operation is atomic.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Data from this "WRITE" will not be mixed with data from another
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
client's "WRITE".
^^^^^^^^^^^^^^^^

NFSv2's requirements are stricter -- so I guess knfsd has to handle this
by locking the inode during an NFSv2 write. Is this done and does
anyone care?

I don't see any similar wording in NFSv3 (rfc1813).

-- Jamie

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/