MIME-Version: 1.0
In-Reply-To: <CA+8MBbKn5DU22RHPYR=vKWpKd1aBu4dm5p57R5U5WTb7KCpMVQ@mail.gmail.com>
References: <a44e1055efc2d2a9473307b22c91caa437aa3f8b.1456439214.git.tony.luck@intel.com>
	<56E1CA7B.5040706@nextfour.com>
	<3908561D78D1C84285E8C5FCA982C28F3A005009@ORSMSX114.amr.corp.intel.com>
	<CA+8MBbKn5DU22RHPYR=vKWpKd1aBu4dm5p57R5U5WTb7KCpMVQ@mail.gmail.com>
Date: Fri, 11 Mar 2016 14:14:44 -0800
Message-ID: <CAPcyv4gX2we6Z2GLt_-WOnzair569g8iot=fKOW1oswO3nt-LA@mail.gmail.com>
Subject: Re: [PATCH v14] x86, mce: Add memcpy_mcsafe()
From: Dan Williams <dan.j.williams@intel.com>
To: Tony Luck <tony.luck@gmail.com>
Cc: =?UTF-8?Q?Mika_Penttil=C3=A4?= <mika.penttila@nextfour.com>,
        Ingo Molnar <mingo@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, Borislav Petkov <bp@alien8.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andy Lutomirski <luto@amacapital.net>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1116
Lines: 28

On Fri, Mar 11, 2016 at 2:10 PM, Tony Luck <tony.luck@gmail.com> wrote:
> On Thu, Mar 10, 2016 at 11:37 AM, Luck, Tony <tony.luck@intel.com> wrote:
>>> But you return 0 == false for success and 1 == true for failure.
>>
>> Aaargh!  -ETOOMUCHSHELLSCRIPTPROGRAMMING
>>
>> -Tony
>
> Options to fix this:
> 1) Just change the comments in the code.
>      This seems like it would confuse people as I thing most people
>      would expect the "true" return to mean the copy succeeded.
> 2) Reverse the return values.
>      Better that option 1 - but doesn't leave scope to return a count
>      if some future user does want to know where the copy failed.
> 3) Change the return type back from "bool" to "int"
>      0 == success, non-zero == fail (with option to put the non-copied
> byte count in later).
> 4) Something else
>

You could return 0 for success and -EIO for failure (positive value
for 'location' if that support ever resurfaces).

That would at least let me drop the ternary conversion I have in
memcpy_from_pmem() [1] to convert bool to an error code.

[1]: https://patchwork.kernel.org/patch/8559521/