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From: Dan Williams <dan.j.williams@intel.com>
Date: Mon, 16 Apr 2018 11:35:33 -0700
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Subject: Re: [PATCH] dax: Change return type to vm_fault_t
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To: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>, linux-nvdimm <linux-nvdimm@lists.01.org>, Linux MM <linux-mm@kvack.org>, Andrew Morton <akpm@linux-foundation.org>, Michal Hocko <mhocko@suse.com>
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On Mon, Apr 16, 2018 at 11:28 AM, Souptick Joarder <jrdr.linux@gmail.com> wrote:
> On Mon, Apr 16, 2018 at 11:51 PM, Matthew Wilcox <willy@infradead.org> wrote:
>> On Mon, Apr 16, 2018 at 11:00:26AM -0700, Dan Williams wrote:
>>> On Mon, Apr 16, 2018 at 10:47 AM, Matthew Wilcox <willy@infradead.org> wrote:
>>> > On Mon, Apr 16, 2018 at 09:14:48AM -0700, Dan Williams wrote:
>>> >> > -       rc = vm_insert_mixed(vmf->vma, vmf->address, pfn);
>>> >> > -
>>> >> > -       if (rc == -ENOMEM)
>>> >> > -               return VM_FAULT_OOM;
>>> >> > -       if (rc < 0 && rc != -EBUSY)
>>> >> > -               return VM_FAULT_SIGBUS;
>>> >> > -
>>> >> > -       return VM_FAULT_NOPAGE;
>>> >> > +       return vmf_insert_mixed(vmf->vma, vmf->address, pfn);
>>> >>
>>> >> Ugh, so this change to vmf_insert_mixed() went upstream without fixing
>>> >> the users? This changelog is now misleading as it does not mention
>>> >> that is now an urgent standalone fix. On first read I assumed this was
>>> >> part of a wider effort for 4.18.
>>> >
>>> > You read too quickly.  vmf_insert_mixed() is a *new* function which
>>> > *replaces* vm_insert_mixed() and
>>> > awful-mangling-of-return-values-done-per-driver.
>>> >
>>> > Eventually vm_insert_mixed() will be deleted.  But today is not that day.
>>>
>>> Ah, ok, thanks for the clarification. Then this patch should
>>> definitely be re-titled to "dax: convert to the new vmf_insert_mixed()
>>> helper". The vm_fault_t conversion is just a minor side-effect of that
>>> larger change. I assume this can wait for v4.18.
>
> The primary objective is to change the return type to
> vm_fault_t in all fault handlers and to support that
> we have replace vm_insert_mixed() with vmf_insert_
> mixed() within one fault handler function.
>
> Do I really need to change the patch title ?

At this point, yes, or at least mention the vm_insert_mixed -->
vmf_insert_mixed conversion in the changelog.