From 65462462ffb28fddf13d46c628c4fc55878ab397 Mon Sep 17 00:00:00 2001 From: John Hubbard Date: Tue, 22 Mar 2022 14:39:40 -0700 Subject: mm/gup: follow_pfn_pte(): -EEXIST cleanup Remove a quirky special case from follow_pfn_pte(), and adjust its callers to match. Caller changes include: __get_user_pages(): Regardless of any FOLL_* flags, get_user_pages() and its variants should handle PFN-only entries by stopping early, if the caller expected **pages to be filled in. This makes for a more reliable API, as compared to the previous approach of skipping over such entries (and thus leaving them silently unwritten). move_pages(): squash the -EEXIST error return from follow_page() into -EFAULT, because -EFAULT is listed in the man page, whereas -EEXIST is not. Link: https://lkml.kernel.org/r/20220204020010.68930-3-jhubbard@nvidia.com Signed-off-by: John Hubbard Suggested-by: Jason Gunthorpe Reviewed-by: Christoph Hellwig Reviewed-by: Jan Kara Cc: Peter Xu Cc: Lukas Bulwahn Cc: Matthew Wilcox Cc: Claudio Imbrenda Cc: Alex Williamson Cc: Andrea Arcangeli Cc: David Hildenbrand Cc: Jason Gunthorpe Cc: Kirill A. Shutemov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/gup.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) (limited to 'mm/gup.c') diff --git a/mm/gup.c b/mm/gup.c index 41da0bd61bec..43ad2bc6ca51 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -464,10 +464,6 @@ static struct page *no_page_table(struct vm_area_struct *vma, static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, pte_t *pte, unsigned int flags) { - /* No page to get reference */ - if (flags & (FOLL_GET | FOLL_PIN)) - return -EFAULT; - if (flags & FOLL_TOUCH) { pte_t entry = *pte; @@ -1205,8 +1201,15 @@ retry: } else if (PTR_ERR(page) == -EEXIST) { /* * Proper page table entry exists, but no corresponding - * struct page. + * struct page. If the caller expects **pages to be + * filled in, bail out now, because that can't be done + * for this page. */ + if (pages) { + ret = PTR_ERR(page); + goto out; + } + goto next_page; } else if (IS_ERR(page)) { ret = PTR_ERR(page); -- cgit v1.2.3-59-g8ed1b