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

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Message-Id: <20200311200023.974009d9a5648b977d5168f6@linux-foundation.org>
Date:   Wed, 11 Mar 2020 20:00:23 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     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 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.