On Fri, May 24, 2019 at 06:45:22PM -0700, john.hubbard@xxxxxxxxx wrote: > 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() I have no objection to this particular patch, but ... > 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. I thought we agreed at LSFMM that the future is a new get_user_bvec() / put_user_bvec(). This is largely going to touch the same places as step 2 in your list above. Is it worth doing step 2? One of the advantages of put_user_bvec() is that it would be quite easy to miss a conversion from put_page() to put_user_page(), but it'll be a type error to miss a conversion from put_page() to put_user_bvec().
