From e07cda5f232fac4de0925d8a4c92e51e41fa2f6e Mon Sep 17 00:00:00 2001
From: David Hildenbrand <david@redhat.com>
Date: Fri, 21 Oct 2022 12:11:39 +0200
Subject: [PATCH] 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.

Link: https://lkml.kernel.org/r/20221021101141.84170-8-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 include/linux/pagewalk.h |  3 +++
 mm/pagewalk.c            | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h
index 37dc0208862d..959f52e5867d 100644
--- a/include/linux/pagewalk.h
+++ b/include/linux/pagewalk.h
@@ -101,6 +101,9 @@ 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 0a5d71aaf9c7..7f1c9b274906 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -517,6 +517,26 @@ int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
 	return walk_pgd_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,
+	};
+
+	if (start >= end || !walk.mm)
+		return -EINVAL;
+	if (start < vma->vm_start || end > vma->vm_end)
+		return -EINVAL;
+
+	mmap_assert_locked(walk.mm);
+	return __walk_page_range(start, end, &walk);
+}
+
 int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
 		void *private)
 {