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()"
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>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
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