[PATCH 1/4] mm/gup: add compound page list iterator
From: Joao Martins <hidden>
Date: 2021-02-03 22:04:02
Also in:
linux-mm, lkml
Subsystem:
memory management, memory management - gup (get user pages), the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
Add an helper that iterates over head pages in a list of pages. It essentially counts the tails until the next page to process has a different head that the current. This is going to be used by unpin_user_pages() family of functions, to batch the head page refcount updates once for all passed consecutive tail pages. Suggested-by: Jason Gunthorpe <jgg@nvidia.com> Signed-off-by: Joao Martins <redacted> --- mm/gup.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+)
diff --git a/mm/gup.c b/mm/gup.c
index d68bcb482b11..4f88dcef39f2 100644
--- a/mm/gup.c
+++ b/mm/gup.c@@ -215,6 +215,35 @@ void unpin_user_page(struct page *page) } EXPORT_SYMBOL(unpin_user_page); +static inline unsigned int count_ntails(struct page **pages, unsigned long npages) +{ + struct page *head = compound_head(pages[0]); + unsigned int ntails; + + for (ntails = 1; ntails < npages; ntails++) { + if (compound_head(pages[ntails]) != head) + break; + } + + return ntails; +} + +static inline void compound_next(unsigned long i, unsigned long npages, + struct page **list, struct page **head, + unsigned int *ntails) +{ + if (i >= npages) + return; + + *ntails = count_ntails(list + i, npages - i); + *head = compound_head(list[i]); +} + +#define for_each_compound_head(i, list, npages, head, ntails) \ + for (i = 0, compound_next(i, npages, list, &head, &ntails); \ + i < npages; i += ntails, \ + compound_next(i, npages, list, &head, &ntails)) + /** * unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages * @pages: array of pages to be maybe marked dirty, and definitely released.
--
2.17.1