4:23 p.m.
On Fri, Oct 20, 2017 at 12:57 AM, Christoph Hellwig <hch(a)lst.de> wrote:
> --- a/arch/powerpc/sysdev/axonram.c
> +++ b/arch/powerpc/sysdev/axonram.c
> @@ -172,6 +172,7 @@ static size_t axon_ram_copy_from_iter(struct dax_device *dax_dev,
pgoff_t pgoff,
>
> static const struct dax_operations axon_ram_dax_ops = {
> .direct_access = axon_ram_dax_direct_access,
> +
> .copy_from_iter = axon_ram_copy_from_iter,
Unrelated whitespace change. That being said - I don't think axonram has
devmap support in any form, so this basically becomes dead code, doesn't
it?
> diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
> index 7abb240847c0..e7e5db07e339 100644
> --- a/drivers/s390/block/dcssblk.c
> +++ b/drivers/s390/block/dcssblk.c
> @@ -52,6 +52,7 @@ static size_t dcssblk_dax_copy_from_iter(struct dax_device
*dax_dev,
>
> static const struct dax_operations dcssblk_dax_ops = {
> .direct_access = dcssblk_dax_direct_access,
> +
> .copy_from_iter = dcssblk_dax_copy_from_iter,
Same comments apply here.
Yes, however it seems these drivers / platforms have been living with
the lack of struct page for a long time. So they either don't use DAX,
or they have a constrained use case that never triggers
get_user_pages(). If it is the latter then they could introduce a new
configuration option that bypasses the pfn_t_devmap() check in
bdev_dax_supported() and fix up the get_user_pages() paths to fail.
So, I'd like to understand how these drivers have been using DAX
support without struct page to see if we need a workaround or we can
go ahead delete this support. If the usage is limited to
execute-in-place perhaps we can do a constrained ->direct_access() for
just that case.