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From:   Souptick Joarder <jrdr.linux@gmail.com>
Date:   Tue, 29 May 2018 21:25:05 +0530
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Subject: Re: [PATCH] mm: Change return type to vm_fault_t
To:     Matthew Wilcox <willy@infradead.org>
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>
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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 ?