Re: [PATCH v7 4/8] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero

[Shiyang Ruan]

On 2021/8/20 10:39, Dan Williams wrote:
> On Sun, Aug 15, 2021 at 11:04 PM Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx> wrote:
> > Punch hole on a reflinked file needs dax_iomap_cow_copy() too.
> > Otherwise, data in not aligned area will be not correct.  So, add the
> > srcmap to dax_iomap_zero() and replace memset() as dax_iomap_cow_copy().
> >
> > Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
> > Reviewed-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
> > Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> > ---
> >   fs/dax.c               | 25 +++++++++++++++----------
> >   fs/iomap/buffered-io.c |  4 ++--
> >   include/linux/dax.h    |  3 ++-
> >   3 files changed, 19 insertions(+), 13 deletions(-)
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index e49ba68cc7e4..91ceb518f66a 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -1198,7 +1198,8 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
> >   }
> >   #endif /* CONFIG_FS_DAX_PMD */
> >
> > -s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap)
> > +s64 dax_iomap_zero(loff_t pos, u64 length, const struct iomap *iomap,
> > +               const struct iomap *srcmap)
> >   {
> >          sector_t sector = iomap_sector(iomap, pos & PAGE_MASK);
> >          pgoff_t pgoff;
> > @@ -1220,19 +1221,23 @@ s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap)
> >
> >          if (page_aligned)
> >                  rc = dax_zero_page_range(iomap->dax_dev, pgoff, 1);
> > -       else
> > +       else {
> >                  rc = dax_direct_access(iomap->dax_dev, pgoff, 1, &kaddr, NULL);
> > -       if (rc < 0) {
> > -               dax_read_unlock(id);
> > -               return rc;
> > -       }
> > -
> > -       if (!page_aligned) {
> > -               memset(kaddr + offset, 0, size);
> > +               if (rc < 0)
> > +                       goto out;
> > +               if (iomap->addr != srcmap->addr) {
> > +                       rc = dax_iomap_cow_copy(pos, size, PAGE_SIZE, srcmap,
> > +                                               kaddr);
>
> Apologies, I'm confused, why is it ok to skip zeroing here?

That was a mistake.  Will be fixed in next version.


--
Thanks,
Ruan.