From: Andrew Morton <akpm@linux-foundation.org>
To: Jules Irenge <jbi.octave@gmail.com>
Cc: boqun.feng@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] backing-dev: refactor wb_congested_put()
Date: Wed, 11 Mar 2020 17:59:19 -0700 [thread overview]
Message-ID: <20200311175919.30523d55b2e5307ba22bbdc0@linux-foundation.org> (raw)
In-Reply-To: <20200312002156.49023-2-jbi.octave@gmail.com>
On Thu, 12 Mar 2020 00:21:56 +0000 Jules Irenge <jbi.octave@gmail.com> wrote:
> wb_congested_put() was written in such a way that made it difficult
> for Sparse tool not to complain
> Expanding the function locking block in the if statement improves on
> the readability of the code. Rewritting it comes with one add-on:
>
> It fixes a warning reported by Sparse tool at wb_congested_put()
>
> warning: context imbalance in wb_congested_put() - unexpected unlock
>
> Refactor the function wb_congested_put()
>
> ...
>
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -464,18 +464,21 @@ void wb_congested_put(struct bdi_writeback_congested *congested)
> {
> unsigned long flags;
>
> - if (!refcount_dec_and_lock_irqsave(&congested->refcnt, &cgwb_lock, &flags))
> - return;
> -
> + if (!refcount_dec_not_one(&congested->refcnt)) {
> + spin_lock_irqsave(&cgwb_lock, flags);
> + if (!refcount_dec_and_test(&congested->refcnt)) {
> + spin_unlock_irqrestore(&cgwb_lock, flags);
> + return;
> + }
> /* bdi might already have been destroyed leaving @congested unlinked */
> - if (congested->__bdi) {
> - rb_erase(&congested->rb_node,
> - &congested->__bdi->cgwb_congested_tree);
> - congested->__bdi = NULL;
> + if (congested->__bdi) {
> + rb_erase(&congested->rb_node,
> + &congested->__bdi->cgwb_congested_tree);
> + congested->__bdi = NULL;
> + }
> + spin_unlock_irqrestore(&cgwb_lock, flags);
> + kfree(congested);
> }
> -
> - spin_unlock_irqrestore(&cgwb_lock, flags);
> - kfree(congested);
> }
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)?
next prev parent reply other threads:[~2020-03-12 0:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-12 0:21 [PATCH 0/1] Refactoring wb_congested_put() Jules Irenge
2020-03-12 0:21 ` [PATCH 1/1] backing-dev: refactor wb_congested_put() Jules Irenge
2020-03-12 0:59 ` Andrew Morton [this message]
2020-03-12 2:29 ` Matthew Wilcox
2020-03-12 3:00 ` Andrew Morton
2020-03-12 9:56 ` Jules Irenge
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