[linux-cifs-client] Add support infrastructure for Named Pipe

[Steve French]

On Mon, Oct 19, 2009 at 2:25 PM, Steve French <smfrench at gmail.com> wrote:
> On Mon, Oct 19, 2009 at 1:54 PM, Gerald Carter <jerry at plainjoe.org> wrote:
>> Steve,
>>
>> Just a few points.  Feel free to ignore or respond.  The only
>> point I'm making here is that other solutions do exist already.
>> I'm not advocating our code as a solution for this debate.
>> Just pointing out that this is a well traveled problem (as you
>> know).
>
> I agree that Likewise librpc would address some of this,

After looking at Jerry's pointer, and to clarify my earlier comment
about the librpc.  The likewise code doesn't look it would help,
especially since it has dependencies on pieces that conflict with
other parts of Linux. The Likewise librpc doesn't appear to map to
Samba's libsmbclient (as Rafal's pitch showed it working in the past
through npmpx), and so doesn't solve the problem for Samba, and it
can't map pipe open/close/read/write through the cifs vfs (so can't
address the problem I mentioned where "NetShareEnum" shows shares on
servers which mount can't reach).   Looking at lwio in more detail, it
is a FUSE module with an upcall to the smb handling code, so can't
handle high stress workloads (a file system which allocates memory in
userspace, or upcalls to userspace, especially in the write patch can
deadlock as we have easily shown in stress testing in the past with
various FS).  FUSE (and thus based user space file systems like
lwio)ares also missing various kernel entry points and opens up bigger
race conditions on calls which are atomic in libc, but not in the vfs
layer.   It also looks like the lw librpc is tightly coupled to the
other pieces of Likewise (which we don't want to get in the way of
Samba and winbind in particular).


-- 
Thanks,

Steve