Re: [PATCH v2] infiniband/mm: convert put_page() to put_user_page*()

[Jason Gunthorpe]

On Fri, May 24, 2019 at 06:45:22PM -0700, john.hubbard@xxxxxxxxx wrote:
> From: John Hubbard <jhubbard@xxxxxxxxxx>
> 
> For infiniband code that retains pages via get_user_pages*(),
> release those pages via the new put_user_page(), or
> put_user_pages*(), instead of put_page()
> 
> This is a tiny part of the second step of fixing the problem described
> in [1]. The steps are:
> 
> 1) Provide put_user_page*() routines, intended to be used
>    for releasing pages that were pinned via get_user_pages*().
> 
> 2) Convert all of the call sites for get_user_pages*(), to
>    invoke put_user_page*(), instead of put_page(). This involves dozens of
>    call sites, and will take some time.
> 
> 3) After (2) is complete, use get_user_pages*() and put_user_page*() to
>    implement tracking of these pages. This tracking will be separate from
>    the existing struct page refcounting.
> 
> 4) Use the tracking and identification of these pages, to implement
>    special handling (especially in writeback paths) when the pages are
>    backed by a filesystem. Again, [1] provides details as to why that is
>    desirable.
> 
> [1] https://lwn.net/Articles/753027/ : "The Trouble with get_user_pages()"
> 
> Cc: Doug Ledford <dledford@xxxxxxxxxx>
> Cc: Jason Gunthorpe <jgg@xxxxxxxx>
> Cc: Mike Marciniszyn <mike.marciniszyn@xxxxxxxxx>
> Cc: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxx>
> Cc: Christian Benvenuti <benve@xxxxxxxxx>
> 
> Reviewed-by: Jan Kara <jack@xxxxxxx>
> Reviewed-by: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxx>
> Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> Reviewed-by: JÃrÃme Glisse <jglisse@xxxxxxxxxx>
> Acked-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
> Tested-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
> ---
>  drivers/infiniband/core/umem.c              |  7 ++++---
>  drivers/infiniband/core/umem_odp.c          | 10 +++++-----
>  drivers/infiniband/hw/hfi1/user_pages.c     | 11 ++++-------
>  drivers/infiniband/hw/mthca/mthca_memfree.c |  6 +++---
>  drivers/infiniband/hw/qib/qib_user_pages.c  | 11 ++++-------
>  drivers/infiniband/hw/qib/qib_user_sdma.c   |  6 +++---
>  drivers/infiniband/hw/usnic/usnic_uiom.c    |  7 ++++---
>  7 files changed, 27 insertions(+), 31 deletions(-)

Applied to for-next, thanks

Jason