Re: [PATCH net-next v3 1/4] mm: page_frag: Introduce page_frag_alloc_align()

[Alexander Duyck <alexander.duyck@gmail.com>]

On Thu, Feb 4, 2021 at 3:06 AM Kevin Hao <haokexin@gmail.com> wrote:
>
> In the current implementation of page_frag_alloc(), it doesn't have
> any align guarantee for the returned buffer address. But for some
> hardwares they do require the DMA buffer to be aligned correctly,
> so we would have to use some workarounds like below if the buffers
> allocated by the page_frag_alloc() are used by these hardwares for
> DMA.
>     buf = page_frag_alloc(really_needed_size + align);
>     buf = PTR_ALIGN(buf, align);
>
> These codes seems ugly and would waste a lot of memories if the buffers
> are used in a network driver for the TX/RX. So introduce
> page_frag_alloc_align() to make sure that an aligned buffer address is
> returned.
>
> Signed-off-by: Kevin Hao <haokexin@gmail.com>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> v3: Use align mask as suggested by Alexander.
>
>  include/linux/gfp.h | 12 ++++++++++--
>  mm/page_alloc.c     |  8 +++++---
>  2 files changed, 15 insertions(+), 5 deletions(-)

Looks good to me.

Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>