The patch titled
Subject: mm/gup: clean up follow_pfn_pte() slightly
has been added to the -mm tree. Its filename is
mm-gup-clean-up-follow_pfn_pte-slightly.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-gup-clean-up-follow_pfn_pte-slightly.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-gup-clean-up-follow_pfn_pte-slightly.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: John Hubbard <jhubbard@xxxxxxxxxx>
Subject: mm/gup: clean up follow_pfn_pte() slightly
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).
Link: https://lkml.kernel.org/r/20220201101108.306062-3-jhubbard@xxxxxxxxxx
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
--- a/mm/gup.c~mm-gup-clean-up-follow_pfn_pte-slightly
+++ a/mm/gup.c
@@ -439,10 +439,6 @@ static struct page *no_page_table(struct
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 +1176,14 @@ 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) {
+ page = ERR_PTR(-EFAULT);
+ goto out;
+ }
goto next_page;
} else if (IS_ERR(page)) {
ret = PTR_ERR(page);
_
Patches currently in -mm which might be from jhubbard@xxxxxxxxxx are
mm-gup-clean-up-follow_pfn_pte-slightly.patch
mm-gup-remove-unused-pin_user_pages_locked.patch
mm-gup-remove-get_user_pages_locked.patch
