linux-kernel - drivers/block/rbd.c: atomic_inc_return_safe() & atomic_dec_return

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Message-ID: <ce2dbec5-00f8-831b-3138-cc4f3b8fdb51@linuxfoundation.org>
Date:   Fri, 2 Oct 2020 16:34:40 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     idryomov@...il.com, dongsheng.yang@...ystack.cn, axboe@...nel.dk
Cc:     ceph-devel@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>
Subject: drivers/block/rbd.c: atomic_inc_return_safe() &
 atomic_dec_return_safe()

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?

thanks,
-- Shuah