linux-kernel - Re: [PATCH v3 05/10] mmap locking API: convert mmap

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Message-ID: <CANN689H=tjNi=g6M776qo8inr+OfAu8mtL5xsJpu4F=dB6R9zA@mail.gmail.com>
Date:   Sat, 28 Mar 2020 00:47:06 -0700
From:   Michel Lespinasse <walken@...gle.com>
To:     Markus Elfring <Markus.Elfring@....de>
Cc:     Coccinelle <cocci@...teme.lip6.fr>, linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        Liam Howlett <Liam.Howlett@...cle.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        David Rientjes <rientjes@...gle.com>,
        Hugh Dickins <hughd@...gle.com>, Ying Han <yinghan@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 05/10] mmap locking API: convert mmap_sem call sites
 missed by coccinelle

Hi Markus,

On Sat, Mar 28, 2020 at 12:37 AM Markus Elfring <Markus.Elfring@....de> wrote:
> > Convert the last few remaining mmap_sem rwsem calls to use the new
> > mmap locking API. These were missed by coccinelle for some reason
>
> Will the clarification of this software situation become more interesting?
>
> > (I think coccinelle does not support some of the preprocessor
> > constructs in these files ?)
>
> I suggest to omit this information from the final change description.
> Would you like to help any more to find nicer solutions
> for remaining open issues?

So, from a practical perspective I think coccinelle has filled its
purpose for me - it got 99% of the job done, and I had to do the last
1% by hand which is not ideal, but really not too bad either. Also, by
using coccinelle I think reviewers can appreciate that the
change is purely mechanical, and reproduce it on their end if needed,
which facilitates the review process greatly.

I would be interested to find out why coccinelle wasn't able to do the
last 1%, but only as part of a long-term learning process on getting
better with coccinelle - I don't consider it a blocker for short-term
progress on this patchset.

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.