linux-kernel - Re: [PATCH v7 3/8] fsdax: Replace mmap entry in case of CoW

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Message-ID: <d4f07aef-ad9f-7de9-c112-a40e2022b399@fujitsu.com>
Date:   Fri, 27 Aug 2021 11:22:21 +0800
From:   Shiyang Ruan <ruansy.fnst@...itsu.com>
To:     Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>
CC:     "Darrick J. Wong" <djwong@...nel.org>,
        linux-xfs <linux-xfs@...r.kernel.org>,
        david <david@...morbit.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux NVDIMM <nvdimm@...ts.linux.dev>,
        Goldwyn Rodrigues <rgoldwyn@...e.de>,
        Al Viro <viro@...iv.linux.org.uk>,
        Matthew Wilcox <willy@...radead.org>,
        Goldwyn Rodrigues <rgoldwyn@...e.com>,
        Ritesh Harjani <riteshh@...ux.ibm.com>
Subject: Re: [PATCH v7 3/8] fsdax: Replace mmap entry in case of CoW



On 2021/8/23 20:57, Christoph Hellwig wrote:
> On Thu, Aug 19, 2021 at 03:54:01PM -0700, Dan Williams wrote:
>>
>> static void *dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf,
>>                                const struct iomap_iter *iter, void
>> *entry, pfn_t pfn,
>>                                unsigned long flags)
>>
>>
>>>   {
>>> +       struct address_space *mapping = vmf->vma->vm_file->f_mapping;
>>>          void *new_entry = dax_make_entry(pfn, flags);
>>> +       bool dirty = insert_flags & DAX_IF_DIRTY;
>>> +       bool cow = insert_flags & DAX_IF_COW;
>>
>> ...and then calculate these flags from the source data. I'm just
>> reacting to "yet more flags".
> 
> Except for the overly long line above that seems like a good idea.
> The iomap_iter didn't exist for most of the time this patch has been
> around.
> 

So should I reuse the iter->flags to pass the insert_flags? (left shift 
it to higher bits)

--
Thanks,
Ruan.