Re: [GIT PULL] kbuild updates for v4.7-rc1

From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Arnd Bergmann" <arnd@arndb.de>, "Michal Marek" <mmarek@suse.com>,
	"Макс Жуков" <mussitantesmortem@gmail.com>,
	nicolas.ferre@atmel.com,
	"Nicolas Pitre" <nicolas.pitre@linaro.org>,
	robert.jarzmik@free.fr, yamada.masahiro@socionext.com,
	"Linux Kbuild mailing list" <linux-kbuild@vger.kernel.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Bob Peterson" <rpeterso@redhat.com>
Subject: Re: [GIT PULL] kbuild updates for v4.7-rc1
Date: Fri, 27 May 2016 22:52:10 +0100	[thread overview]
Message-ID: <20160527215210.GU14480@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+55aFzQ4oe6cT5xf=3xT1d6ji2L_her8AmJxpsixFw_GavDvg@mail.gmail.com>

On Fri, May 27, 2016 at 01:20:29PM -0700, Linus Torvalds wrote:

> I didn't look at the details of your patch, but I did look at several
> IS_ERR_VALUE() uses in the standard kernel, and they were basically
> all wrong. Even the ones that used it for the rigth reason (vm_brk()
> that returns a pointer or an error in an "unsigned long") had actively
> screwed up and truncated that (correct) unsigned long value to "int"
> before doing the IS_ERR_VALUE(), which made it all wrong again.
> 
> And the other users just looked entirely bogus, and were all just
> "zero or negative error code" that has nothing to do with
> IS_ERR_VALUE(). The code should just check against zero, not use that
> macro that was designed for something different.

Both gfs2 ones and the one in fs/romfs are crap.  AFS one is simply ridiculous -
        result = generic_file_write_iter(iocb, from);
        if (IS_ERR_VALUE(result)) {
                _leave(" = %zd", result);
                return result;
        }

        _leave(" = %zd", result);
        return result;
In binfmt*.c some callers are valid (vm_mmap and vm_brk values; BTW, the
code in binfmt_flat.c checks for vm_mmap returning 0, which should never
happen, AFAICS).  Most of binfmt_flat.c ones are pure cargo-culting.

net/9p/client.c ones are results of serious mistake in design of 9P.L
extensions to 9P - they assume that numeric values of E... are
architecture-independent and send them over the wire.  The uses of
IS_ERR_VALUE there are papering over that.  Badly.

A couple of sound/* ones should be simply "is negative".

netfilter ones are caused by bad calling conventions of
xt_percpu_counter_alloc().

I hadn't looked through drivers/* users, but judging by fs/, net/ and sound/,
I would expect them to be pointless garbage in the best case and red flags
for broken code in the worst.

IMO IS_ERR_VALUE() should be renamed to something less generic and be used
a lot less than it is right now.