On Thu, May 23, 2019 at 12:25:37AM -0700, john.hubb...@gmail.com wrote:
> From: John Hubbard <jhubb...@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 <dledf...@redhat.com>
> Cc: Jason Gunthorpe <j...@ziepe.ca>
> Cc: Mike Marciniszyn <mike.marcinis...@intel.com>
> Cc: Dennis Dalessandro <dennis.dalessan...@intel.com>
> Cc: Christian Benvenuti <be...@cisco.com>
>
> Reviewed-by: Jan Kara <j...@suse.cz>
> Reviewed-by: Dennis Dalessandro <dennis.dalessan...@intel.com>
> Acked-by: Jason Gunthorpe <j...@mellanox.com>
> Tested-by: Ira Weiny <ira.we...@intel.com>
> Signed-off-by: John Hubbard <jhubb...@nvidia.com>
Reviewed-by: Jérôme Glisse <jgli...@redhat.com>
Between i have a wishlist see below
> ---
> 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(-)
>
> diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
> index e7ea819fcb11..673f0d240b3e 100644
> --- a/drivers/infiniband/core/umem.c
> +++ b/drivers/infiniband/core/umem.c
> @@ -54,9 +54,10 @@ static void __ib_umem_release(struct ib_device *dev,
> struct ib_umem *umem, int d
>
> for_each_sg_page(umem->sg_head.sgl, &sg_iter, umem->sg_nents, 0) {
> page = sg_page_iter_page(&sg_iter);
> - if (!PageDirty(page) && umem->writable && dirty)
> - set_page_dirty_lock(page);
> - put_page(page);
> + if (umem->writable && dirty)
> + put_user_pages_dirty_lock(&page, 1);
> + else
> + put_user_page(page);
Can we get a put_user_page_dirty(struct page 8*pages, bool dirty, npages) ?
It is a common pattern that we might have to conditionaly dirty the pages
and i feel it would look cleaner if we could move the branch within the
put_user_page*() function.
Cheers,
Jérôme
