From: Jens Axboe <axboe@kernel.dk>
To: Shuah Khan <skhan@linuxfoundation.org>,
idryomov@gmail.com, dongsheng.yang@easystack.cn
Cc: ceph-devel@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Kees Cook <keescook@chromium.org>
Subject: Re: drivers/block/rbd.c: atomic_inc_return_safe() & atomic_dec_return_safe()
Date: Fri, 2 Oct 2020 17:44:22 -0600 [thread overview]
Message-ID: <c2dd3223-bda1-be8c-fbc4-9c0eec63bc9d@kernel.dk> (raw)
In-Reply-To: <ce2dbec5-00f8-831b-3138-cc4f3b8fdb51@linuxfoundation.org>
On 10/2/20 4:34 PM, Shuah Khan wrote:
> All,
>
> I came across these atomic_inc_return_safe() & atomic_dec_return_safe()
> functions that hold the counters at safe values.
>
> atomic_inc_return_safe()
>
> If the counter is already 0 it will not be incremented.
> If the counter is already at its maximum value returns
> -EINVAL without updating it.
>
> atomic_dec_return_safe()
>
> Decrement the counter. Return the resulting value, or -EINVAL
>
> These two routines are static and only used in rbd.c.
>
> Can these become part of atomic_t ops?
I think you just want to use refcount_t for this use case. They
have safe guards for under/overflow.
--
Jens Axboe
next prev parent reply other threads:[~2020-10-02 23:44 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-02 22:34 Shuah Khan
2020-10-02 23:44 ` Jens Axboe [this message]
2020-10-02 23:50 ` Shuah Khan
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