Re: compat: autofs v5 packet size ambiguity - update

[Linus Torvalds]

On Tue, Feb 21, 2012 at 7:33 PM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> But I'm sure that the autofs daemon does something simple that we can
> depend on in practice.

I didn't find the most recent source code, but the first thing that
automount.c does after calling "mount" (which is a for+exec, so we
cannot take the mounting is_compat_task() into account is to open the
new root for the ioctlfd, and then it does a stat.

And then it does a AUTOFS_IOC_PROTOVER ioctl to see what the protocol
version is.

So we could just decide that

 (a) we add a mount option for the packet size (or just "v6" - which
would be "v5 with a fixed packet size")

 (b) in the absence of an explicit mount option, we look at
is_compat_task() for the first AUTOFS_IOC_PROTOVER ioctl we get.

That looks fairly straightforward and safe. Hmm?

Where are the automount sources supposed to be, anyway? kernel.org has
a v5 directory, but it's empty.

                Linus
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