Re: [PATCH 1/5] uio: remove copy_from_iter_flushcache() and copy_mc_to_iter()

Dan Williams
2021-12-12T14:22:32Z

On Wed, Dec 8, 2021 at 10:38 PM Christoph Hellwig <hch@lst.de> wrote:
>
> These two wrappers are never used.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> drivers/nvdimm/pmem.c | 4 ++--
> include/linux/uio.h | 20 +-------------------
> 2 files changed, 3 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index 4190c8c46ca88..8294f1c701baa 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -302,8 +302,8 @@ static long pmem_dax_direct_access(struct dax_device *dax_dev,
> }
>
> /*
> - * Use the 'no check' versions of copy_from_iter_flushcache() and
> - * copy_mc_to_iter() to bypass HARDENED_USERCOPY overhead. Bounds
> + * Use the 'no check' versions of _copy_from_iter_flushcache() and
> + * _copy_mc_to_iter() to bypass HARDENED_USERCOPY overhead. Bounds
> * checking, both file offset and device offset, is handled by
> * dax_iomap_actor()
> */

This comment change does not make sense since it is saying why pmem is
using the "_" versions. However, I assume this whole comment goes away
in a later patch.

> diff --git a/include/linux/uio.h b/include/linux/uio.h
> index 6350354f97e90..494d552c1d663 100644
> --- a/include/linux/uio.h
> +++ b/include/linux/uio.h
> @@ -196,7 +196,7 @@ bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
> #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
> /*
> * Note, users like pmem that depend on the stricter semantics of
> - * copy_from_iter_flushcache() than copy_from_iter_nocache() must check for
> + * _copy_from_iter_flushcache() than _copy_from_iter_nocache() must check for
> * IS_ENABLED(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) before assuming that the
> * destination is flushed from the cache on return.
> */

Same here.

> @@ -211,24 +211,6 @@ size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
> #define _copy_mc_to_iter _copy_to_iter
> #endif
>
> -static __always_inline __must_check
> -size_t copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
> -{
> - if (unlikely(!check_copy_size(addr, bytes, false)))
> - return 0;
> - else
> - return _copy_from_iter_flushcache(addr, bytes, i);
> -}
> -
> -static __always_inline __must_check
> -size_t copy_mc_to_iter(void *addr, size_t bytes, struct iov_iter *i)
> -{
> - if (unlikely(!check_copy_size(addr, bytes, true)))
> - return 0;
> - else
> - return _copy_mc_to_iter(addr, bytes, i);
> -}
> -
> size_t iov_iter_zero(size_t bytes, struct iov_iter *);
> unsigned long iov_iter_alignment(const struct iov_iter *i);
> unsigned long iov_iter_gap_alignment(const struct iov_iter *i);
> --
> 2.30.2
>