On Tue 21-05-19 10:46:25, Darrick J. Wong wrote:
> On Mon, Apr 29, 2019 at 12:26:39PM -0500, Goldwyn Rodrigues wrote:
> > From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> >
> > Change dax_iomap_pfn to return the address as well in order to
> > use it for performing a memcpy in case the type is IOMAP_DAX_COW.
> > We don't handle PMD because btrfs does not support hugepages.
> >
> > Question:
> > The sequence of bdev_dax_pgoff() and dax_direct_access() is
> > used multiple times to calculate address and pfn's. Would it make
> > sense to call it while calculating address as well to reduce code?
> >
> > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> > ---
> > fs/dax.c | 19 +++++++++++++++----
> > 1 file changed, 15 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index 610bfa861a28..718b1632a39d 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -984,7 +984,7 @@ static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
> > }
> >
> > static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
> > - pfn_t *pfnp)
> > + pfn_t *pfnp, void **addr)
> > {
> > const sector_t sector = dax_iomap_sector(iomap, pos);
> > pgoff_t pgoff;
> > @@ -996,7 +996,7 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
> > return rc;
> > id = dax_read_lock();
> > length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
> > - NULL, pfnp);
> > + addr, pfnp);
> > if (length < 0) {
> > rc = length;
> > goto out;
> > @@ -1286,6 +1286,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
> > XA_STATE(xas, &mapping->i_pages, vmf->pgoff);
> > struct inode *inode = mapping->host;
> > unsigned long vaddr = vmf->address;
> > + void *addr;
> > loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
> > struct iomap iomap = { 0 };
>
> Ugh, I had forgotten that fs/dax.c open-codes iomap_apply, probably
> because the actor returns vm_fault_t, not bytes copied. I guess that
> makes it a tiny bit more complicated to pass in two (struct iomap *) to
> the iomap_begin function...
Hum, right. We could actually reimplement dax_iomap_{pte|pmd}_fault() using
iomap_apply(). We would just need to propagate error code out of our
'actor' inside the structure pointed to by 'data'. But that's doable.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
