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

Jason Gunthorpe
2019-05-27T23:12:44Z

On Fri, May 24, 2019 at 06:45:22PM -0700, john.hubbard@gmail.com wrote:
> From: John Hubbard <jhubbard@nvidia.com>
>
> 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@redhat.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
> Cc: Dennis Dalessandro <dennis.dalessandro@intel.com>
> Cc: Christian Benvenuti <benve@cisco.com>
>
> Reviewed-by: Jan Kara <jack@suse.cz>
> Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
> Reviewed-by: Jérôme Glisse <jglisse@redhat.com>
> Acked-by: Jason Gunthorpe <jgg@mellanox.com>
> Tested-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
> 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