linux-kernel - [PATCH 13/22] mm/hmm: Use lockdep instead of comments

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Date:   Mon,  1 Jul 2019 08:20:11 +0200
From:   Christoph Hellwig <hch@....de>
To:     Dan Williams <dan.j.williams@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Ben Skeggs <bskeggs@...hat.com>
Cc:     Ira Weiny <ira.weiny@...el.com>, linux-mm@...ck.org,
        nouveau@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-nvdimm@...ts.01.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, John Hubbard <jhubbard@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Souptick Joarder <jrdr.linux@...il.com>,
        Philip Yang <Philip.Yang@....com>
Subject: [PATCH 13/22] mm/hmm: Use lockdep instead of comments

From: Jason Gunthorpe <jgg@...lanox.com>

So we can check locking at runtime.

Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
Reviewed-by: Jérôme Glisse <jglisse@...hat.com>
Reviewed-by: John Hubbard <jhubbard@...dia.com>
Reviewed-by: Ralph Campbell <rcampbell@...dia.com>
Acked-by: Souptick Joarder <jrdr.linux@...il.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Tested-by: Philip Yang <Philip.Yang@....com>
---
 mm/hmm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index 1eddda45cefa..6f5dc6d568fe 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -246,11 +246,11 @@ static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
  *
  * To start mirroring a process address space, the device driver must register
  * an HMM mirror struct.
- *
- * THE mm->mmap_sem MUST BE HELD IN WRITE MODE !
  */
 int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
 {
+	lockdep_assert_held_exclusive(&mm->mmap_sem);
+
 	/* Sanity check */
 	if (!mm || !mirror || !mirror->ops)
 		return -EINVAL;
-- 
2.20.1