[RFC PATCH 05/14] mm/khugepaged: add mmap_assert_locked() checks to scan_pmd()

From: "Zach O'Keefe" <zokeefe@google.com>
To: Alex Shi <alex.shi@linux.alibaba.com>,
	David Hildenbrand <david@redhat.com>,
	 David Rientjes <rientjes@google.com>,
	Michal Hocko <mhocko@suse.com>,
	 Pasha Tatashin <pasha.tatashin@soleen.com>,
	SeongJae Park <sj@kernel.org>,  Song Liu <songliubraving@fb.com>,
	Vlastimil Babka <vbabka@suse.cz>, Zi Yan <ziy@nvidia.com>,
	 linux-mm@kvack.org
Cc: Andrea Arcangeli <aarcange@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	 Arnd Bergmann <arnd@arndb.de>,
	Axel Rasmussen <axelrasmussen@google.com>,
	 Chris Kennelly <ckennelly@google.com>,
	Chris Zankel <chris@zankel.net>, Helge Deller <deller@gmx.de>,
	 Hugh Dickins <hughd@google.com>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	 "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
	Jens Axboe <axboe@kernel.dk>,
	 "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Matthew Wilcox <willy@infradead.org>,
	 Matt Turner <mattst88@gmail.com>,
	Max Filippov <jcmvbkbc@gmail.com>,
	 Miaohe Lin <linmiaohe@huawei.com>,
	Minchan Kim <minchan@kernel.org>,
	 Patrick Xia <patrickx@google.com>,
	Pavel Begunkov <asml.silence@gmail.com>,
	 Peter Xu <peterx@redhat.com>,
	Richard Henderson <rth@twiddle.net>,
	 Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Yang Shi <shy828301@gmail.com>,
	 "Zach O'Keefe" <zokeefe@google.com>
Subject: [RFC PATCH 05/14] mm/khugepaged: add mmap_assert_locked() checks to scan_pmd()
Date: Tue,  8 Mar 2022 13:34:08 -0800	[thread overview]
Message-ID: <20220308213417.1407042-6-zokeefe@google.com> (raw)
In-Reply-To: <20220308213417.1407042-1-zokeefe@google.com>

scan_pmd() requires mmap_lock held in read. Add a lockdep assertion to
guard this condition, as scan_pmd() will be called from other contexts
later in the series.

Signed-off-by: Zach O'Keefe <zokeefe@google.com>
---
 mm/khugepaged.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index b204bc1eefa7..56f2ef7146c7 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1253,6 +1253,7 @@ struct scan_pmd_result {
 	struct page *head;
 };
 
+/* Called with mmap_lock held and does not drop it. */
 static void scan_pmd(struct mm_struct *mm,
 		     struct vm_area_struct *vma,
 		     unsigned long address,
@@ -1267,6 +1268,7 @@ static void scan_pmd(struct mm_struct *mm,
 	spinlock_t *ptl;
 	int node = NUMA_NO_NODE;
 
+	mmap_assert_locked(mm);
 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
 
 	pmd = mm_find_pmd(mm, address);
-- 
2.35.1.616.g0bdcbb4464-goog


