There is the concern that unpin_user_page_range_dirty_lock() might do some weird merging of PFN ranges -- either now or in the future -- such that PFN range is contiguous but the page range might not be.
Let's sanity-check for that and drop the nth_page() usage.
Reviewed-by: Lorenzo Stoakes lorenzo.stoakes@oracle.com Signed-off-by: David Hildenbrand david@redhat.com --- mm/gup.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/mm/gup.c b/mm/gup.c index f0f4d1a68e094..010fe56f6e132 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -237,7 +237,7 @@ void folio_add_pin(struct folio *folio) static inline struct folio *gup_folio_range_next(struct page *start, unsigned long npages, unsigned long i, unsigned int *ntails) { - struct page *next = nth_page(start, i); + struct page *next = start + i; struct folio *folio = page_folio(next); unsigned int nr = 1;
@@ -342,6 +342,10 @@ EXPORT_SYMBOL(unpin_user_pages_dirty_lock); * "gup-pinned page range" refers to a range of pages that has had one of the * pin_user_pages() variants called on that page. * + * The page range must be truly physically contiguous: the page range + * corresponds to a contiguous PFN range and all pages can be iterated + * naturally. + * * For the page ranges defined by [page .. page+npages], make that range (or * its head pages, if a compound page) dirty, if @make_dirty is true, and if the * page range was previously listed as clean. @@ -359,6 +363,8 @@ void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages, struct folio *folio; unsigned int nr;
+ VM_WARN_ON_ONCE(!page_range_contiguous(page, npages)); + for (i = 0; i < npages; i += nr) { folio = gup_folio_range_next(page, npages, i, &nr); if (make_dirty && !folio_test_dirty(folio)) {