Commit 65462462 authored Mar 22, 2022 by John Hubbard Committed by Linus Torvalds Mar 22, 2022

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 <jhubbard@nvidia.com>
Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Peter Xu <peterx@redhat.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 7196040e

mm/gup.c

+8 −5

Original line number	Diff line number	Diff line
		@@ -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 @@ 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) {
		ret = PTR_ERR(page);
		goto out;
		}

		goto next_page;
		} else if (IS_ERR(page)) {
		ret = PTR_ERR(page);

mm/migrate.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -1761,6 +1761,13 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
		continue;
		}

		/*
		* The move_pages() man page does not have an -EEXIST choice, so
		* use -EFAULT instead.
		*/
		if (err == -EEXIST)
		err = -EFAULT;

		/*
		* If the page is already on the target node (!err), store the
		* node, otherwise, store the err.