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Date:      Tue, 04 Nov 2008 09:15:09 +1100
From:      Antony Mawer <fbsd-fs@mawer.org>
To:        Attilio Rao <attilio@freebsd.org>
Cc:        freebsd-fs@freebsd.org, developers@freebsd.org, Yuri Pankov <yuri.pankov@gmail.com>, freebsd-current@freebsd.org, Robert Watson <rwatson@freebsd.org>
Subject:   Re: reproducible panic with mount_smbfs
Message-ID:  <490F77ED.9050501@mawer.org>
In-Reply-To: <3bbf2fe10811031320o5d977babpe37bcf22836b8d34@mail.gmail.com>
References:  <20081102123100.GA1434@darklight.homeunix.org>	<3bbf2fe10811020737g211dfb3fs54b48e4071db2393@mail.gmail.com>	<3bbf2fe10811020817g1409a38ep26c1ee8edf075201@mail.gmail.com>	<200811031458.42549.jhb@freebsd.org>	<alpine.BSF.1.10.0811032106110.48320@fledge.watson.org> <3bbf2fe10811031320o5d977babpe37bcf22836b8d34@mail.gmail.com>

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Attilio Rao wrote:
> 2008/11/3, Robert Watson <rwatson@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



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