Re: [PATCH v3 1/4] mm/gup: add compound page list iterator

[Jason Gunthorpe]

On Fri, Feb 05, 2021 at 08:41:24PM +0000, Joao Martins wrote:
> Add an helper that iterates over head pages in a list of pages. It
> essentially counts the tails until the next page to process has a
> different head that the current. This is going to be used by
> unpin_user_pages() family of functions, to batch the head page refcount
> updates once for all passed consecutive tail pages.
> 
> Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
> Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
> ---
>  mm/gup.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)

Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

This can be used for check_and_migrate_cma_pages() too (there is a
series around to change this logic though, not sure if it is landed
yet)

Jason