linux-kernel - Re: [PATCH v5] fs: dax: Adding new return type vm_fault

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Message-ID: <CAFqt6zatfzk8PmBN110LD_x8goU+vO4U9TAGaamJ4UqwRm+g_g@mail.gmail.com>
Date:   Tue, 24 Apr 2018 11:29:39 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     jack@...e.cz, Al Viro <viro@...iv.linux.org.uk>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Michal Hocko <mhocko@...e.com>,
        kirill.shutemov@...ux.intel.com,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] fs: dax: Adding new return type vm_fault_t

On Tue, Apr 24, 2018 at 1:19 AM, Matthew Wilcox <willy@...radead.org> wrote:
> On Mon, Apr 23, 2018 at 11:36:25PM +0530, Souptick Joarder wrote:
>> If the insertion of PTE failed because someone else
>> already added a different entry in the mean time, we
>> treat that as success as we assume the same entry was
>> actually inserted.
>
> No, Jan said to *make it a comment*.  In the source file.  That's why
> he formatted it with the /* */.  Not in the changelog.
Sorry, got confused.

I think this should be fine -

+/*
+If the insertion of PTE failed because someone else
+already added a different entry in the mean time, we
+treat that as success as we assume the same entry was
+actually inserted.
+*/

-int vm_insert_mixed_mkwrite(struct vm_area_struct *vma, unsigned long addr,
-                       pfn_t pfn)
+vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma,
+               unsigned long addr, pfn_t pfn)
 {
-       return __vm_insert_mixed(vma, addr, pfn, true);
+       int err;
+
+       err =  __vm_insert_mixed(vma, addr, pfn, true);
+       if (err == -ENOMEM)
+               return VM_FAULT_OOM;
+       if (err < 0 && err != -EBUSY)
+               return VM_FAULT_SIGBUS;
+       return VM_FAULT_NOPAGE;
 }
-EXPORT_SYMBOL(vm_insert_mixed_mkwrite);
+EXPORT_SYMBOL(vmf_insert_mixed_mkwrite);