Re: [PATCH v9 5/8] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero
On Thu, Sep 16, 2021 at 04:49:19PM +0800, Shiyang Ruan wrote:
>
>
> On 2021/9/16 14:16, Christoph Hellwig wrote:
> > On Wed, Sep 15, 2021 at 06:44:58PM +0800, Shiyang Ruan wrote:
> > > + rc = dax_direct_access(iomap->dax_dev, pgoff, 1, , NULL);
> > > + if (rc < 0)
> > > + goto out;
> > > + memset(kaddr + offset, 0, size);
> > > + if (srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) {
> >
> > Should we also check that ->dax_dev for iomap and srcmap are different
> > first to deal with case of file system with multiple devices?
>
> I have not thought of this case. Isn't it possible to CoW between different
> devices?
There's nothing in the iomap API that prevents a filesystem from doing
that, though there are no filesystems today that do such a thing.
That said, if btrfs ever joins the fold (and adds DAX support) then they
could totally COW to a different device.
--D
>
>
> --
> Thanks,
> Ruan
>
> >
> > Otherwise looks good:
> >
> > Reviewed-by: Christoph Hellwig
> >
>
>
Re: [PATCH v9 5/8] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero
On 2021/9/16 14:16, Christoph Hellwig wrote:
On Wed, Sep 15, 2021 at 06:44:58PM +0800, Shiyang Ruan wrote:
+ rc = dax_direct_access(iomap->dax_dev, pgoff, 1, , NULL);
+ if (rc < 0)
+ goto out;
+ memset(kaddr + offset, 0, size);
+ if (srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) {
Should we also check that ->dax_dev for iomap and srcmap are different
first to deal with case of file system with multiple devices?
I have not thought of this case. Isn't it possible to CoW between
different devices?
--
Thanks,
Ruan
Otherwise looks good:
Reviewed-by: Christoph Hellwig
Re: [PATCH v9 5/8] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero
On Wed, Sep 15, 2021 at 06:44:58PM +0800, Shiyang Ruan wrote:
> + rc = dax_direct_access(iomap->dax_dev, pgoff, 1, , NULL);
> + if (rc < 0)
> + goto out;
> + memset(kaddr + offset, 0, size);
> + if (srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) {
Should we also check that ->dax_dev for iomap and srcmap are different
first to deal with case of file system with multiple devices?
Otherwise looks good:
Reviewed-by: Christoph Hellwig
