linux-kernel - Re: [PATCH v1] xfs: initialize error in xfs_defer_finish

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Date:   Wed, 3 Aug 2022 23:42:21 +0000
From:   Sherry Yang <sherry.yang@...cle.com>
To:     "Darrick J. Wong" <djwong@...nel.org>
CC:     Dave Chinner <david@...morbit.com>,
        "dchinner@...hat.com" <dchinner@...hat.com>,
        Allison Henderson <allison.henderson@...cle.com>,
        "chandanrlinux@...il.com" <chandanrlinux@...il.com>,
        "bfoster@...hat.com" <bfoster@...hat.com>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] xfs: initialize error in xfs_defer_finish_one


> On Aug 2, 2022, at 9:31 PM, Darrick J. Wong <djwong@...nel.org> wrote:
> 
> On Tue, Aug 02, 2022 at 06:49:02AM +1000, Dave Chinner wrote:
>> On Mon, Aug 01, 2022 at 12:03:11PM -0700, Sherry Yang wrote:
>>> Path through non-void function 'xfs_defer_finish_one' may return error
>>> uninitialized if no iteration of 'list_for_each_safe' occurs. Fix this
>>> by initializing error.
>> 
>> I didn't think this situation was possible - how do we get deferred
>> work queued with no work items on it?
>> 
>> If we can return an uninitialised error from xfs_defer_finish_one()
>> because of an empty queued work, then something else has gone wrong
>> earlier in the work deferral process. If this can actually happen,
>> then we need to fix whatever is creating the empty work rather than
>> paper over it by initialising the error being returned for empty
>> works...
> 
> /me bets this is a response to a static checker that doesn't know that
> list_empty(&dfp->dfp_work) == false in all circumstances.  It's not
> possible for tp->t_dfops to contain an xfs_defer_pending with no work
> items.

Hi Darrick, 

You’re correct. This is a false positive bug detected by our static code 
analysis tool. Sorry for the noise.

Sherry
> 
> --D
> 
>> Cheers,
>> 
>> Dave.
>> -- 
>> Dave Chinner
>> david@...morbit.com