reproducible panic with mount_smbfs

[Antony Mawer]

Attilio Rao wrote:
> 2008/11/3, Robert Watson <rwatson at freebsd.org>:
>> On Mon, 3 Nov 2008, John Baldwin wrote:
>>>> Yuri, could you please test this fix:
>> http://www.freebsd.org/~attilio/netsmb.diff
>>>> and report if it works? You could get a KASSERT running but this is
>> expected as I want to identify on the callers who passes a malformed request
>> and fix it.
>>> This allows all smb locks to recurse unlike the original code I think.  It
>> may be better if smb_vclist was initialized with LK_RECURSE, but not all the
>> other smb locks.  Also, in smb_co_addchild() I think you should just replace
>> the existing asserts with appropriate lockmgr_assert() (you could add a
>> smb_co_assert() to preserve the layering) rather than removing assertions
>> altogether.
>>  My general feeling is that the locking in netsmb needs a bit of cleanup,
>> updating, etc.  I'm reluctant to change the underlying primitives (as this
>> patch does) without first clarifying what's going on in the code a layer or
>> two above.
> 
> I agree with Robert.
> We need to make an upper layers analysis and decide what is the best
> solution for locks.
> This was a quick hack just to let it not panic when mounting.

This probably also applies to NWFS and netncp as well -- I haven't had a 
chance to test NWFS in 7.x as of yet, but will hope to do so in the 
coming months...

--Antony