linux-kernel - [PATCH v2] mm/mmap: Don't unlock VMAs in remap_file

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Date:   Tue, 15 Dec 2020 10:54:41 -0500
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...gle.com>
Subject: [PATCH v2] mm/mmap: Don't unlock VMAs in remap_file_pages()

do_mmap() will unlock the necessary VMAs.  There is also a bug in the
loop which will evaluate as false and not unlock any VMAs anyways.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 18 +-----------------
 1 file changed, 1 insertion(+), 17 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 5c8b4485860de..f7fecb77f84fd 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3025,25 +3025,9 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 
 	flags &= MAP_NONBLOCK;
 	flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
-	if (vma->vm_flags & VM_LOCKED) {
-		struct vm_area_struct *tmp;
+	if (vma->vm_flags & VM_LOCKED)
 		flags |= MAP_LOCKED;
 
-		/* drop PG_Mlocked flag for over-mapped range */
-		for (tmp = vma; tmp->vm_start >= start + size;
-				tmp = tmp->vm_next) {
-			/*
-			 * Split pmd and munlock page on the border
-			 * of the range.
-			 */
-			vma_adjust_trans_huge(tmp, start, start + size, 0);
-
-			munlock_vma_pages_range(tmp,
-					max(tmp->vm_start, start),
-					min(tmp->vm_end, start + size));
-		}
-	}
-
 	file = get_file(vma->vm_file);
 	ret = do_mmap(vma->vm_file, start, size,
 			prot, flags, pgoff, &populate, NULL);
-- 
2.28.0