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Date: Tue, 29 May 2018 10:34:45 -0700
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH] mm: Change return type to vm_fault_t
Message-ID: <20180529173445.GD15148@bombadil.infradead.org>
References: <20180529143126.GA19698@jordon-HP-15-Notebook-PC>
 <20180529145055.GA15148@bombadil.infradead.org>
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To: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>, Hugh Dickins <hughd@google.com>, Andrew Morton <akpm@linux-foundation.org>, Michal Hocko <mhocko@suse.com>, Ross Zwisler <ross.zwisler@linux.intel.com>, zi.yan@cs.rutgers.edu, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Dan Williams <dan.j.williams@intel.com>, Greg KH <gregkh@linuxfoundation.org>, Mark Rutland <mark.rutland@arm.com>, riel@redhat.com, pasha.tatashin@oracle.com, jschoenh@amazon.de, Kate Stewart <kstewart@linuxfoundation.org>, David Rientjes <rientjes@google.com>, tglx@linutronix.de, Peter Zijlstra <peterz@infradead.org>, Mel Gorman <mgorman@suse.de>, yang.s@alibaba-inc.com, Minchan Kim <minchan@kernel.org>, linux-fsdevel <linux-fsdevel@vger.kernel.org>, linux-kernel@vger.kernel.org, Linux-MM <linux-mm@kvack.org>

On Tue, May 29, 2018 at 09:25:05PM +0530, Souptick Joarder wrote:
> On Tue, May 29, 2018 at 8:20 PM, Matthew Wilcox <willy@infradead.org> wrote:
> > On Tue, May 29, 2018 at 08:01:26PM +0530, Souptick Joarder wrote:
> >> Use new return type vm_fault_t for fault handler. For
> >> now, this is just documenting that the function returns
> >> a VM_FAULT value rather than an errno. Once all instances
> >> are converted, vm_fault_t will become a distinct type.
> >
> > I don't believe you've checked this with sparse.
> >
> >> @@ -802,7 +802,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
> >>                    bool *unlocked)
> >>  {
> >>       struct vm_area_struct *vma;
> >> -     int ret, major = 0;
> >> +     int major = 0;
> >> +     vm_fault_t ret;
> >>
> >>       if (unlocked)
> >>               fault_flags |= FAULT_FLAG_ALLOW_RETRY;
> >
> > ...
> >         major |= ret & VM_FAULT_MAJOR;
> >
> > That should be throwing a warning.
> 
> Sorry, but I verified again and didn't see similar warnings.
> 
> steps followed -
> 
> apply the patch
> make c=2 -j4 ( build for x86_64)
> looking for warnings in files because of this patch.
> 
> The only error I am seeing "error: undefined identifier '__COUNTER__' "
> which is pointing to BUG(). There are few warnings but those are not
> related to this patch.
> 
> In my test tree the final patch to create new vm_fault_t type is
> already applied.
> 
> Do you want me to verify in some other way ?

I see:

mm/gup.c:817:15: warning: invalid assignment: |=
mm/gup.c:817:15:    left side has type int
mm/gup.c:817:15:    right side has type restricted vm_fault_t

are you building with 'c=2' or 'C=2'?