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From: peterx@redhat.com
To: linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Cc: Matthew Wilcox <willy@infradead.org>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
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	Yang Shi <shy828301@gmail.com>,
	James Houghton <jthoughton@google.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Jason Gunthorpe <jgg@nvidia.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	peterx@redhat.com,
	Axel Rasmussen <axelrasmussen@google.com>
Subject: [PATCH 05/13] mm: Introduce vma_pgtable_walk_{begin|end}()
Date: Tue, 19 Dec 2023 15:55:30 +0800
Message-ID: <20231219075538.414708-6-peterx@redhat.com>
In-Reply-To: <20231219075538.414708-1-peterx@redhat.com>
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From: Peter Xu <peterx@redhat.com>

Introduce per-vma begin()/end() helpers for pgtable walks.  This is a
preparation work to merge hugetlb pgtable walkers with generic mm.

The helpers need to be called before and after a pgtable walk, will start
to be needed if the pgtable walker code supports hugetlb pages.  It's a
hook point for any type of VMA, but for now only hugetlb uses it to
stablize the pgtable pages from getting away (due to possible pmd
unsharing).

Reviewed-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/linux/mm.h |  3 +++
 mm/memory.c        | 12 ++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index b72bf25a45cf..85e43775824b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4181,4 +4181,7 @@ static inline bool pfn_is_unaccepted_memory(unsigned long pfn)
 	return range_contains_unaccepted_memory(paddr, paddr + PAGE_SIZE);
 }
 
+void vma_pgtable_walk_begin(struct vm_area_struct *vma);
+void vma_pgtable_walk_end(struct vm_area_struct *vma);
+
 #endif /* _LINUX_MM_H */
diff --git a/mm/memory.c b/mm/memory.c
index 1795aba53cf5..9ac6a9db971e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6270,3 +6270,15 @@ void ptlock_free(struct ptdesc *ptdesc)
 	kmem_cache_free(page_ptl_cachep, ptdesc->ptl);
 }
 #endif
+
+void vma_pgtable_walk_begin(struct vm_area_struct *vma)
+{
+	if (is_vm_hugetlb_page(vma))
+		hugetlb_vma_lock_read(vma);
+}
+
+void vma_pgtable_walk_end(struct vm_area_struct *vma)
+{
+	if (is_vm_hugetlb_page(vma))
+		hugetlb_vma_unlock_read(vma);
+}
-- 
2.41.0