linux-kernel - [PATCH v2 6/9] mm/pagewalk: don't trigger test_walk() in walk_page

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Date:   Fri, 21 Oct 2022 12:11:38 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.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 v2 6/9] mm/pagewalk: don't trigger test_walk() in walk_page_vma()

As Peter points out, the caller passes a single VMA and can just do that
check itself.

And in fact, no existing users rely on test_walk() getting called. So let's
just remove it and make the implementation slightly more efficient.

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 include/linux/pagewalk.h | 2 ++
 mm/pagewalk.c            | 7 -------
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h
index f3fafb731ffd..37dc0208862d 100644
--- a/include/linux/pagewalk.h
+++ b/include/linux/pagewalk.h
@@ -27,6 +27,8 @@ struct mm_walk;
  *			"do page table walk over the current vma", returning
  *			a negative value means "abort current page table walk
  *			right now" and returning 1 means "skip the current vma"
+ *			Note that this callback is not called when the caller
+ *			passes in a single VMA as for walk_page_vma().
  * @pre_vma:            if set, called before starting walk on a non-null vma.
  * @post_vma:           if set, called after a walk on a non-null vma, provided
  *                      that @pre_vma and the vma walk succeeded.
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 2ff3a5bebceb..0a5d71aaf9c7 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -526,18 +526,11 @@ int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
 		.vma		= vma,
 		.private	= private,
 	};
-	int err;
 
 	if (!walk.mm)
 		return -EINVAL;
 
 	mmap_assert_locked(walk.mm);
-
-	err = walk_page_test(vma->vm_start, vma->vm_end, &walk);
-	if (err > 0)
-		return 0;
-	if (err < 0)
-		return err;
 	return __walk_page_range(vma->vm_start, vma->vm_end, &walk);
 }
 
-- 
2.37.3