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

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Message-ID: <20210823125715.GA15536@lst.de>
Date:   Mon, 23 Aug 2021 14:57:15 +0200
From:   Christoph Hellwig <hch@....de>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Shiyang Ruan <ruansy.fnst@...itsu.com>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Christoph Hellwig <hch@....de>,
        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 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.