On Tue, Mar 26, 2019 at 02:02:54PM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
>
> dax_iomap_cow copies a page before presenting for mmap.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> ---
> fs/dax.c | 33 ++++++++++++++++++++++++++++++++-
> 1 file changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index e254535dd830..21ee3df6f02c 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -1269,6 +1269,33 @@ static bool dax_fault_is_synchronous(unsigned long flags,
> && (iomap->flags & IOMAP_F_DIRTY);
> }
>
> +static int dax_iomap_cow(struct iomap *iomap, loff_t pos, pfn_t *pfn)
> +{
> + void *daddr;
> + pgoff_t pgoff;
> + long rc;
> + int id;
> + sector_t sector;
> +
> + pos = round_down(pos, PAGE_SIZE);
> +
> + sector = round_down(iomap->addr + iomap->offset - pos, PAGE_SIZE) >> 9;
> + rc = bdev_dax_pgoff(iomap->bdev, sector, PAGE_SIZE, &pgoff);
> + if (rc)
> + return rc;
> +
> + id = dax_read_lock();
> + rc = dax_direct_access(iomap->dax_dev, pgoff, 1, &daddr, pfn);
> + if (rc < 0)
> + goto out;
> +
> + dax_to_dax_copy(iomap, pos, daddr, PAGE_SIZE);
> +
> +out:
> + dax_read_unlock(id);
> + return rc;
> +}
> +
> static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
> int *iomap_errp, const struct iomap_ops *ops)
> {
> @@ -1372,7 +1399,11 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
> count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
> major = VM_FAULT_MAJOR;
> }
> - error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
> +
> + if (iomap.flags & IOMAP_F_COW)
> + error = dax_iomap_cow(&iomap, pos, &pfn);
Why wouldn't dax_iomap_cow also apply to dax_iomap_pmd_fault?
--D
> + else
> + error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
> if (error < 0)
> goto error_finish_iomap;
>
> --
> 2.16.4
>
