linux-kernel - Re: [PATCH 2/2] mm/gup: fix a misnamed "write" argument: should be "flags"

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Message-ID: <20191014164513.GA6839@iweiny-DESK2.sc.intel.com>
Date:   Mon, 14 Oct 2019 09:45:14 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
Cc:     "Kirill A. Shutemov" <kirill@...temov.name>,
        John Hubbard <jhubbard@...dia.com>,
        kbuild test robot <lkp@...el.com>, kbuild-all@...ts.01.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@...radead.org>,
        Keith Busch <keith.busch@...el.com>,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH 2/2] mm/gup: fix a misnamed "write" argument: should be
 "flags"

On Mon, Oct 14, 2019 at 08:14:04PM +0530, Aneesh Kumar K.V wrote:
> On 10/14/19 7:22 PM, Kirill A. Shutemov wrote:
> > On Sun, Oct 13, 2019 at 11:43:10PM -0700, John Hubbard wrote:
> > > On 10/13/19 11:12 PM, kbuild test robot wrote:
> > > > Hi John,
> > > > 
> > > > Thank you for the patch! Yet something to improve:
> > > > 
> > > > [auto build test ERROR on linus/master]
> > > > [cannot apply to v5.4-rc3 next-20191011]
> > > > [if your patch is applied to the wrong git tree, please drop us a note to help
> > > > improve the system. BTW, we also suggest to use '--base' option to specify the
> > > > base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
> > > > 
> > > > url:    https://github.com/0day-ci/linux/commits/John-Hubbard/gup-c-gup_benchmark-c-trivial-fixes-before-the-storm/20191014-114158
> > > > config: powerpc-defconfig (attached as .config)
> > > > compiler: powerpc64-linux-gcc (GCC) 7.4.0
> > > > reproduce:
> > > >           wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > > >           chmod +x ~/bin/make.cross
> > > >           # save the attached .config to linux build tree
> > > >           GCC_VERSION=7.4.0 make.cross ARCH=powerpc
> > > > 
> > > > If you fix the issue, kindly add following tag
> > > > Reported-by: kbuild test robot <lkp@...el.com>
> > > > 
> > > > All errors (new ones prefixed by >>):
> > > > 
> > > >      mm/gup.c: In function 'gup_hugepte':
> > > > > > mm/gup.c:1990:33: error: 'write' undeclared (first use in this function); did you mean 'writeq'?
> > > >        if (!pte_access_permitted(pte, write))
> > > >                                       ^~~~~
> > > >                                       writeq
> > > >      mm/gup.c:1990:33: note: each undeclared identifier is reported only once for each function it appears in
> > > > 
> > > 
> > > OK, so this shows that my cross-compiler test scripts are faulty lately,
> > > sorry I missed this.
> > > 
> > > But more importantly, the above missed case is an example of when "write" really
> > > means "write", as opposed to meaning flags.
> > > 
> > > Please put this patch on hold or drop it, until we hear from the authors as to how
> > > they would like to resolve this. I suspect it will end up as something like:
> > > 
> > > 	bool write = (flags & FOLL_WRITE);
> > > 
> > > ...perhaps?
> > 
> > Just use
> > 
> > 	if (!pte_access_permitted(pte, flags & FOLL_WRITE))
> > 
> > as we have in gup_pte_range().
> > 
> > And add:
> > 
> > Fixes: cbd34da7dc9a ("mm: move the powerpc hugepd code to mm/gup.c")
> > 
> 
> b798bec4741bdd80224214fdd004c8e52698e42 isn't this the commit that need to
> be mentioned in the Fixes: tag?

Yes, and while we are at it the type should probably be changed to unsigned
int.

Ira

> 
> -aneesh