linux-kernel - [PATCH v4 04/13] mm: Introduce vma_pgtable_walk

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Message-ID: <20240327152332.950956-5-peterx@redhat.com>
Date: Wed, 27 Mar 2024 11:23:23 -0400
From: peterx@...hat.com
To: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc: Yang Shi <shy828301@...il.com>,
	"Kirill A . Shutemov" <kirill@...temov.name>,
	Mike Kravetz <mike.kravetz@...cle.com>,
	John Hubbard <jhubbard@...dia.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	peterx@...hat.com,
	Andrew Jones <andrew.jones@...ux.dev>,
	Muchun Song <muchun.song@...ux.dev>,
	linux-riscv@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	Lorenzo Stoakes <lstoakes@...il.com>,
	Matthew Wilcox <willy@...radead.org>,
	Rik van Riel <riel@...riel.com>,
	linux-arm-kernel@...ts.infradead.org,
	Andrea Arcangeli <aarcange@...hat.com>,
	David Hildenbrand <david@...hat.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@...nel.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	James Houghton <jthoughton@...gle.com>,
	Jason Gunthorpe <jgg@...dia.com>,
	Mike Rapoport <rppt@...nel.org>,
	Axel Rasmussen <axelrasmussen@...gle.com>
Subject: [PATCH v4 04/13] mm: Introduce vma_pgtable_walk_{begin|end}()

From: Peter Xu <peterx@...hat.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@...radead.org>
Reviewed-by: Muchun Song <muchun.song@...ux.dev>
Signed-off-by: Peter Xu <peterx@...hat.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 afe27ff3fa94..d8f78017d271 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4233,4 +4233,7 @@ 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 3d0c0cc33c57..27d173f9a521 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6438,3 +6438,15 @@ 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);
+}
-- 
2.44.0