[merged mm-stable] mm-khugepaged-check-compound_order-in-collapse_pte_mapped_thp.patch removed from -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The quilt patch titled
     Subject: mm/khugepaged: check compound_order() in collapse_pte_mapped_thp()
has been removed from the -mm tree.  Its filename was
     mm-khugepaged-check-compound_order-in-collapse_pte_mapped_thp.patch

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

------------------------------------------------------
From: "Zach O'Keefe" <zokeefe@google.com>
Subject: mm/khugepaged: check compound_order() in collapse_pte_mapped_thp()
Date: Thu, 22 Sep 2022 15:27:31 -0700

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>
---

 mm/khugepaged.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/mm/khugepaged.c~mm-khugepaged-check-compound_order-in-collapse_pte_mapped_thp
+++ a/mm/khugepaged.c
@@ -1399,6 +1399,9 @@ void collapse_pte_mapped_thp(struct mm_s
 	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;
 
_

Patches currently in -mm which might be from zokeefe@google.com are