linux-kernel - [PATCH v1 5/7] mm/pagewalk: add walk_page_range

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Date:   Fri, 30 Sep 2022 16:19:29 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>, Hugh Dickins <hughd@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Peter Xu <peterx@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Jason Gunthorpe <jgg@...dia.com>,
        John Hubbard <jhubbard@...dia.com>
Subject: [PATCH v1 5/7] mm/pagewalk: add walk_page_range_vma()

Let's add walk_page_range_vma(), which is similar to walk_page_vma(),
however, is only interested in a subset of the VMA range.

To be used in KSM code to stop using follow_page() next.

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 include/linux/pagewalk.h |  3 +++
 mm/pagewalk.c            | 27 +++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h
index f3fafb731ffd..2f8f6cc980b4 100644
--- a/include/linux/pagewalk.h
+++ b/include/linux/pagewalk.h
@@ -99,6 +99,9 @@ int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
 			  unsigned long end, const struct mm_walk_ops *ops,
 			  pgd_t *pgd,
 			  void *private);
+int walk_page_range_vma(struct vm_area_struct *vma, unsigned long start,
+			unsigned long end, const struct mm_walk_ops *ops,
+			void *private);
 int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
 		void *private);
 int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 131b2b335b2c..757c075da231 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -514,6 +514,33 @@ int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
 	return __walk_page_range(start, end, &walk);
 }
 
+int walk_page_range_vma(struct vm_area_struct *vma, unsigned long start,
+			unsigned long end, const struct mm_walk_ops *ops,
+			void *private)
+{
+	struct mm_walk walk = {
+		.ops		= ops,
+		.mm		= vma->vm_mm,
+		.vma		= vma,
+		.private	= private,
+	};
+	int err;
+
+	if (start >= end || !walk.mm)
+		return -EINVAL;
+	if (start < vma->vm_start || end > vma->vm_end)
+		return -EINVAL;
+
+	mmap_assert_locked(walk.mm);
+
+	err = walk_page_test(start, end, &walk);
+	if (err > 0)
+		return 0;
+	if (err < 0)
+		return err;
+	return __walk_page_range(start, end, &walk);
+}
+
 int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
 		void *private)
 {
-- 
2.37.3