From: Matthew Wilcox <willy@infradead.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
linux-mm@kvack.org, Shaohua Li <shli@kernel.org>,
linux-raid@vger.kernel.org,
Anna-Maria Gleixner <anna-maria@linutronix.de>
Subject: Re: [PATCH 3/8] md: raid5: use refcount_t for reference counting instead atomic_t
Date: Wed, 23 May 2018 06:21:19 -0700 [thread overview]
Message-ID: <20180523132119.GC19987@bombadil.infradead.org> (raw)
In-Reply-To: <20180509193645.830-4-bigeasy@linutronix.de>
On Wed, May 09, 2018 at 09:36:40PM +0200, Sebastian Andrzej Siewior wrote:
> refcount_t type and corresponding API should be used instead of atomic_t when
> the variable is used as a reference counter. This allows to avoid accidental
> refcounter overflows that might lead to use-after-free situations.
>
> Most changes are 1:1 replacements except for
> BUG_ON(atomic_inc_return(&sh->count) != 1);
>
> which has been turned into
> refcount_inc(&sh->count);
> BUG_ON(refcount_read(&sh->count) != 1);
@@ -5387,7 +5387,8 @@ static struct stripe_head *__get_priority_stripe(struct
+r5conf *conf, int group)
sh->group = NULL;
}
list_del_init(&sh->lru);
- BUG_ON(atomic_inc_return(&sh->count) != 1);
+ refcount_inc(&sh->count);
+ BUG_ON(refcount_read(&sh->count) != 1);
return sh;
}
That's the only problematic usage. And I think what it's really saying is:
BUG_ON(refcount_read(&sh->count) != 0);
refcount_set(&sh->count, 1);
With that, this looks like a reasonable use of refcount_t to me.
next prev parent reply other threads:[~2018-05-23 13:21 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-09 19:36 [PATCH v2 0/8] Introduce refcount_dec_and_lock_irqsave() Sebastian Andrzej Siewior
2018-05-09 19:36 ` [PATCH 1/8] bdi: use refcount_t for reference counting instead atomic_t Sebastian Andrzej Siewior
2018-05-09 19:36 ` [PATCH 2/8] userns: " Sebastian Andrzej Siewior
2018-05-09 19:36 ` [PATCH 3/8] md: raid5: " Sebastian Andrzej Siewior
2018-05-23 12:36 ` Peter Zijlstra
2018-05-23 12:50 ` Sebastian Andrzej Siewior
2018-05-23 12:55 ` Peter Zijlstra
2018-05-23 13:21 ` Matthew Wilcox [this message]
2018-05-23 17:49 ` Peter Zijlstra
2018-05-23 19:22 ` Shaohua Li
2018-05-24 7:14 ` Peter Zijlstra
2018-05-09 19:36 ` [PATCH 4/8] locking/refcount: implement refcount_dec_and_lock_irqsave() Sebastian Andrzej Siewior
2018-05-09 19:36 ` [PATCH 5/8] bdi: Use irqsave variant of refcount_dec_and_lock() Sebastian Andrzej Siewior
2018-05-09 19:36 ` [PATCH 6/8] userns: " Sebastian Andrzej Siewior
2018-05-09 19:36 ` [PATCH 7/8] md: raid5: " Sebastian Andrzej Siewior
2018-05-09 19:36 ` [PATCH 8/8] md: raid5: Do not disable irq on release_inactive_stripe_list() call Sebastian Andrzej Siewior
2018-05-23 13:01 ` [PATCH v2 0/8] Introduce refcount_dec_and_lock_irqsave() Peter Zijlstra
2018-05-23 13:09 ` Sebastian Andrzej Siewior
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