Commit 7cad96ae authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

mm/gup: fix handling of errors from arch_make_folio_accessible() in follow_page_pte() 

In case we call arch_make_folio_accessible() and it fails, we would
incorrectly return a value that is "!= 0" to the caller, indicating that
we pinned all requested pages and that the caller can keep going.

follow_page_pte() is not supposed to return error values, but instead "0"
on failure and "1" on success -- we'll clean that up separately.

In case we return "!= 0", the caller will just keep going pinning more
pages.  If we happen to pin a page afterwards, we're in trouble, because
we essentially skipped some pages in the requested range.

Staring at the arch_make_folio_accessible() implementation on s390x, I
assume it should actually never really fail unless something unexpected
happens (BUG?).  So let's not CC stable and just fix common code to do the
right thing.

Clean up the code a bit now that there is no reason to store the return
value of arch_make_folio_accessible().

Link: https://lkml.kernel.org/r/20250908094517.303409-1-david@redhat.com


Fixes: f28d4363 ("mm/gup/writeback: add callbacks for inaccessible pages")
Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarClaudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent e7a5f249

mm/gup.c

+3 −6
Original line number Diff line number Diff line
@@ -2898,13 +2898,10 @@ static int gup_fast_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, 
		 * see Documentation/core-api/pin_user_pages.rst for

		 * details.

		 */

		if (flags & FOLL_PIN) {

			ret = arch_make_folio_accessible(folio);

			if (ret) {

		if ((flags & FOLL_PIN) && arch_make_folio_accessible(folio)) {

			gup_put_folio(folio, 1, flags);

			goto pte_unmap;

		}

		}

		folio_set_referenced(folio);

		pages[*nr] = page;

		(*nr)++;