mm/khugepaged: check compound_order() in collapse_pte_mapped_thp()
By the time we lock a page in collapse_pte_mapped_thp(), the page mapped by the address pushed onto the slot's .pte_mapped_thp[] array might have changed arbitrarily since we last looked at it. We revalidate that the page is still the head of a compound page, but we don't revalidate if the compound page is of order HPAGE_PMD_ORDER before applying rmap and page table updates. Since the kernel now supports large folios of arbitrary order, and since replacing page's pte mappings by a pmd mapping only makes sense for compound pages of order HPAGE_PMD_ORDER, revalidate that the compound order is indeed of order HPAGE_PMD_ORDER before proceeding. Link: https://lore.kernel.org/linux-mm/CAHbLzkon+2ky8v9ywGcsTUgXM_B35jt5NThYqQKXW2YV_GUacw@mail.gmail.com/ Link: https://lkml.kernel.org/r/20220922222731.1124481-1-zokeefe@google.comSigned-off-by: Zach O'Keefe <zokeefe@google.com> Suggested-by: Yang Shi <shy828301@gmail.com> Reviewed-by: Yang Shi <shy828301@gmail.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: Chris Kennelly <ckennelly@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Houghton <jthoughton@google.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Rongwei Wang <rongwei.wang@linux.alibaba.com> Cc: SeongJae Park <sj@kernel.org> Cc: Song Liu <songliubraving@fb.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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