reproducible panic with mount_smbfs

[Robert Watson]

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.

Robert N M Watson
Computer Laboratory
University of Cambridge