linux-kernel - Re: [PATCH 1/1] backing-dev: refactor wb_congested

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Date:   Thu, 12 Mar 2020 09:56:01 +0000 (GMT)
From:   Jules Irenge <jbi.octave@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Matthew Wilcox <willy@...radead.org>,
        Jules Irenge <jbi.octave@...il.com>, boqun.feng@...il.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] backing-dev: refactor wb_congested_put()



On Wed, 11 Mar 2020, Andrew Morton wrote:

> On Wed, 11 Mar 2020 19:29:48 -0700 Matthew Wilcox <willy@...radead.org> wrote:
> 
> > On Wed, Mar 11, 2020 at 05:59:19PM -0700, Andrew Morton wrote:
> > > hm, it's hard to get excited over this.  Open-coding the
> > > refcount_dec_and_lock_irqsave() internals at a callsite in order to
> > > make sparse happy.
> > > 
> > > Is there some other way, using __acquires (for example)?
> > 
> > sparse is really bad at conditional lock acquisition. 
> 
> I can well imagine.
> 
> > we have similar
> > problems over the vfs.  but we shouldn't be obfuscating our code to make
> > the tool happy.
> 
> Perhaps sparse needs a way of being directed to suppress checking
> across a particular function.
> 
> 
Thanks for the feedback, maybe this is a limitation for Sparse.

I have experienced quite often this problem.