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authorZach O'Keefe <zokeefe@google.com>2022-09-23 01:27:31 +0300
committerAndrew Morton <akpm@linux-foundation.org>2022-10-04 00:03:32 +0300
commit780a4b6fb865534fcb3aa9150942f3a719d11ce9 (patch)
tree14c69ce8e03be4fd439e8393414aaee698362ccd /mm/khugepaged.c
parent958f32ce832ba781ac20e11bb2d12a9352ea28fc (diff)
downloadlinux-780a4b6fb865534fcb3aa9150942f3a719d11ce9.tar.xz
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.com Signed-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>
Diffstat (limited to 'mm/khugepaged.c')
-rw-r--r--mm/khugepaged.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 57af2c841b41..40fd9f7b3ed3 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1399,6 +1399,9 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr)
if (!PageHead(hpage))
goto drop_hpage;
+ if (compound_order(hpage) != HPAGE_PMD_ORDER)
+ goto drop_hpage;
+
if (find_pmd_or_thp_or_none(mm, haddr, &pmd) != SCAN_SUCCEED)
goto drop_hpage;