The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x bc3fe6805cf09a25a086573a17d40e525208c5d8 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025041752-tightwad-catwalk-8586@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From bc3fe6805cf09a25a086573a17d40e525208c5d8 Mon Sep 17 00:00:00 2001 From: David Hildenbrand david@redhat.com Date: Mon, 10 Feb 2025 20:37:44 +0100 Subject: [PATCH] mm/rmap: reject hugetlb folios in folio_make_device_exclusive()

Even though FOLL_SPLIT_PMD on hugetlb now always fails with -EOPNOTSUPP, let's add a safety net in case FOLL_SPLIT_PMD usage would ever be reworked.

In particular, before commit 9cb28da54643 ("mm/gup: handle hugetlb in the generic follow_page_mask code"), GUP(FOLL_SPLIT_PMD) would just have returned a page. In particular, hugetlb folios that are not PMD-sized would never have been prone to FOLL_SPLIT_PMD.

hugetlb folios can be anonymous, and page_make_device_exclusive_one() is not really prepared for handling them at all. So let's spell that out.

Link: https://lkml.kernel.org/r/20250210193801.781278-3-david@redhat.com Fixes: b756a3b5e7ea ("mm: device exclusive memory access") Signed-off-by: David Hildenbrand david@redhat.com Reviewed-by: Alistair Popple apopple@nvidia.com Tested-by: Alistair Popple apopple@nvidia.com Cc: Alex Shi alexs@kernel.org Cc: Danilo Krummrich dakr@kernel.org Cc: Dave Airlie airlied@gmail.com Cc: Jann Horn jannh@google.com Cc: Jason Gunthorpe jgg@nvidia.com Cc: Jerome Glisse jglisse@redhat.com Cc: John Hubbard jhubbard@nvidia.com Cc: Jonathan Corbet corbet@lwn.net Cc: Karol Herbst kherbst@redhat.com Cc: Liam Howlett liam.howlett@oracle.com Cc: Lorenzo Stoakes lorenzo.stoakes@oracle.com Cc: Lyude lyude@redhat.com Cc: "Masami Hiramatsu (Google)" mhiramat@kernel.org Cc: Oleg Nesterov oleg@redhat.com Cc: Pasha Tatashin pasha.tatashin@soleen.com Cc: Peter Xu peterx@redhat.com Cc: Peter Zijlstra (Intel) peterz@infradead.org Cc: SeongJae Park sj@kernel.org Cc: Simona Vetter simona.vetter@ffwll.ch Cc: Vlastimil Babka vbabka@suse.cz Cc: Yanteng Si si.yanteng@linux.dev Cc: Barry Song v-songbaohua@oppo.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org

diff --git a/mm/rmap.c b/mm/rmap.c index c6c4d4ea29a7..17fbfa61f7ef 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2499,7 +2499,7 @@ static bool folio_make_device_exclusive(struct folio *folio, * Restrict to anonymous folios for now to avoid potential writeback * issues. */ - if (!folio_test_anon(folio)) + if (!folio_test_anon(folio) || folio_test_hugetlb(folio)) return false;

rmap_walk(folio, &rwc);