Messages in this thread Patch in this message | | | From | John Hubbard <> | Subject | [PATCH v3 2/4] mm/gup: clean up follow_pfn_pte() slightly | Date | Thu, 3 Feb 2022 01:32:30 -0800 |
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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).
Cc: Peter Xu <peterx@redhat.com> Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com> Suggested-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Signed-off-by: John Hubbard <jhubbard@nvidia.com> --- mm/gup.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c index 65575ae3602f..cad3f28492e3 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -439,10 +439,6 @@ 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; @@ -1180,8 +1176,13 @@ static long __get_user_pages(struct mm_struct *mm, } 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) + goto out; + goto next_page; } else if (IS_ERR(page)) { ret = PTR_ERR(page); -- 2.35.1
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