Re: [PATCH 17/29] fsdax: factor out a dax_memzero helper

Darrick J. Wong
2021-11-23T22:45:00Z

On Tue, Nov 23, 2021 at 01:22:13PM -0800, Dan Williams wrote:
> On Tue, Nov 9, 2021 at 12:34 AM Christoph Hellwig <hch@lst.de> wrote:
> >
> > Factor out a helper for the "manual" zeroing of a DAX range to clean
> > up dax_iomap_zero a lot.
> >
>
> Small / optional fixup below:
>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
>
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > ---
> > fs/dax.c | 36 +++++++++++++++++++-----------------
> > 1 file changed, 19 insertions(+), 17 deletions(-)
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index d7a923d152240..dc9ebeff850ab 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -1121,34 +1121,36 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
> > }
> > #endif /* CONFIG_FS_DAX_PMD */
> >
> > +static int dax_memzero(struct dax_device *dax_dev, pgoff_t pgoff,
> > + unsigned int offset, size_t size)
> > +{
> > + void *kaddr;
> > + long rc;
> > +
> > + rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr, NULL);
> > + if (rc >= 0) {
>
> Technically this should be "> 0" because dax_direct_access() returns
> nr_available_pages @pgoff, but this isn't broken because
> dax_direct_access() converts the "zero pages available" case into
> -ERANGE.

Agreed. With that fixed,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

>
> > + memset(kaddr + offset, 0, size);
> > + dax_flush(dax_dev, kaddr + offset, size);
> > + }
> > + return rc;
> > +}
> > +
> > s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap)
> > {
> > pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
> > long rc, id;
> > - void *kaddr;
> > - bool page_aligned = false;
> > unsigned offset = offset_in_page(pos);
> > unsigned size = min_t(u64, PAGE_SIZE - offset, length);
> >
> > - if (IS_ALIGNED(pos, PAGE_SIZE) && size == PAGE_SIZE)
> > - page_aligned = true;
> > -
> > id = dax_read_lock();
> > -
> > - if (page_aligned)
> > + if (IS_ALIGNED(pos, PAGE_SIZE) && size == PAGE_SIZE)
> > rc = dax_zero_page_range(iomap->dax_dev, pgoff, 1);
> > 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);
> > - dax_flush(iomap->dax_dev, kaddr + offset, size);
> > - }
> > + rc = dax_memzero(iomap->dax_dev, pgoff, offset, size);
> > dax_read_unlock(id);
> > +
> > + if (rc < 0)
> > + return rc;
> > return size;
> > }
> >
> > --
> > 2.30.2
> >