| Message ID | 20230817064934.3424431-2-vivek.kasireddy@intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | udmabuf: Add support for page migration out of movable zone or CMA | expand |
On Wed, Aug 16, 2023 at 11:49:32PM -0700, Vivek Kasireddy wrote: > For drivers that would like to migrate pages out of the movable > zone (or CMA) in order to pin them (longterm) for DMA, using > check_and_migrate_movable_pages() directly provides a convenient > option instead of duplicating similar checks (e.g, checking > the folios for zone, hugetlb, etc) and calling migrate_pages() > directly. > > Ideally, a driver is expected to call pin_user_pages(FOLL_LONGTERM) > to migrate and pin the pages for longterm DMA but there are > situations where the GUP APIs cannot be used directly for > various reasons (e.g, when the VMA or start addr cannot be > easily determined but the relevant pages are available). No way this should be an exposed API. Please add an API that does the migration and pinning in one useful helper, including one to undo the pin. Then properly document it, and ensure it is a _GPL export.
diff --git a/include/linux/mm.h b/include/linux/mm.h index 406ab9ea818f..81871ffd3ff9 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1547,6 +1547,8 @@ void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages, void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages, bool make_dirty); void unpin_user_pages(struct page **pages, unsigned long npages); +long check_and_migrate_movable_pages(unsigned long nr_pages, + struct page **pages); static inline bool is_cow_mapping(vm_flags_t flags) { diff --git a/mm/gup.c b/mm/gup.c index 76d222ccc3ff..18beda89fcf3 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2141,8 +2141,8 @@ static int migrate_longterm_unpinnable_pages( * If everything is OK and all pages in the range are allowed to be pinned, then * this routine leaves all pages pinned and returns zero for success. */ -static long check_and_migrate_movable_pages(unsigned long nr_pages, - struct page **pages) +long check_and_migrate_movable_pages(unsigned long nr_pages, + struct page **pages) { unsigned long collected; LIST_HEAD(movable_page_list); @@ -2156,12 +2156,13 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages, pages); } #else -static long check_and_migrate_movable_pages(unsigned long nr_pages, - struct page **pages) +long check_and_migrate_movable_pages(unsigned long nr_pages, + struct page **pages) { return 0; } #endif /* CONFIG_MIGRATION */ +EXPORT_SYMBOL(check_and_migrate_movable_pages); /* * __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
For drivers that would like to migrate pages out of the movable zone (or CMA) in order to pin them (longterm) for DMA, using check_and_migrate_movable_pages() directly provides a convenient option instead of duplicating similar checks (e.g, checking the folios for zone, hugetlb, etc) and calling migrate_pages() directly. Ideally, a driver is expected to call pin_user_pages(FOLL_LONGTERM) to migrate and pin the pages for longterm DMA but there are situations where the GUP APIs cannot be used directly for various reasons (e.g, when the VMA or start addr cannot be easily determined but the relevant pages are available). Cc: David Hildenbrand <david@redhat.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Hugh Dickins <hughd@google.com> Cc: Peter Xu <peterx@redhat.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Gerd Hoffmann <kraxel@redhat.com> Cc: Dongwon Kim <dongwon.kim@intel.com> Cc: Junxiao Chang <junxiao.chang@intel.com> Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com> --- include/linux/mm.h | 2 ++ mm/gup.c | 9 +++++---- 2 files changed, 7 insertions(+), 4 deletions(-)