[merged mm-hotfixes-stable] mm-avoid-vm_bug_on-when-try-to-map-an-anon-large-folio-to-zero-page.patch removed from -mm tree

[merged mm-hotfixes-stable] mm-avoid-vm_bug_on-when-try-to-map-an-anon-large-folio-to-zero-page.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm: avoid VM_BUG_ON when try to map an anon large folio to zero page.
has been removed from the -mm tree.  Its filename was
     mm-avoid-vm_bug_on-when-try-to-map-an-anon-large-folio-to-zero-page.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Zi Yan <ziy@nvidia.com>
Subject: mm: avoid VM_BUG_ON when try to map an anon large folio to zero page.
Date: Wed, 23 Oct 2024 13:12:36 -0400

An anonymous large folio can be split into non order-0 folios,
try_to_map_unused_to_zeropage() should not VM_BUG_ON compound pages but
just return false.  This fixes the crash when splitting anonymous large
folios to non order-0 folios.

Link: https://lkml.kernel.org/r/20241023171236.1122535-1-ziy@nvidia.com
Fixes: b1f202060afe ("mm: remap unused subpages to shared zeropage when splitting isolated thp")
Signed-off-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Usama Arif <usamaarif642@gmail.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/migrate.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/mm/migrate.c~mm-avoid-vm_bug_on-when-try-to-map-an-anon-large-folio-to-zero-page
+++ a/mm/migrate.c
@@ -206,7 +206,8 @@ static bool try_to_map_unused_to_zeropag
 	pte_t newpte;
 	void *addr;
 
-	VM_BUG_ON_PAGE(PageCompound(page), page);
+	if (PageCompound(page))
+		return false;
 	VM_BUG_ON_PAGE(!PageAnon(page), page);
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
 	VM_BUG_ON_PAGE(pte_present(*pvmw->pte), page);
_

Patches currently in -mm which might be from ziy@nvidia.com are

mm-avoid-zeroing-user-movable-page-twice-with-init_on_alloc=1.patch
mm-avoid-zeroing-user-movable-page-twice-with-init_on_alloc=1-fix.patch