Commit e0fc2037 authored by Zi Yan's avatar Zi Yan Committed by Andrew Morton
Browse files

mm: avoid VM_BUG_ON when try to map an anon large folio to zero page. 

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: b1f20206 ("mm: remap unused subpages to shared zeropage when splitting isolated thp")
Signed-off-by: default avatarZi Yan <ziy@nvidia.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Acked-by: default avatarUsama 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f4657e16

mm/migrate.c

+2 −1
Original line number Diff line number Diff line
@@ -206,7 +206,8 @@ static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw, 
	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);