diff --git a/include/linux/mm.h b/include/linux/mm.h
index 956025940053..5b5f26d6588a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2922,6 +2922,9 @@ extern int do_munmap(struct mm_struct *, unsigned long, size_t,
 extern int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int behavior);
 
 #ifdef CONFIG_MMU
+extern int do_vma_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
+			 unsigned long start, unsigned long end,
+			 struct list_head *uf, bool downgrade);
 extern int __mm_populate(unsigned long addr, unsigned long len,
 			 int ignore_errors);
 static inline void mm_populate(unsigned long addr, unsigned long len)
diff --git a/ipc/shm.c b/ipc/shm.c
index 1c6a6b319a49..60e45e7045d4 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -1786,8 +1786,8 @@ long ksys_shmdt(char __user *shmaddr)
 			 */
 			file = vma->vm_file;
 			size = i_size_read(file_inode(vma->vm_file));
-			do_vmi_munmap(&vmi, mm, vma->vm_start,
-			      vma->vm_end - vma->vm_start, NULL, false);
+			do_vma_munmap(&vmi, vma, vma->vm_start, vma->vm_end,
+				      NULL, false);
 			/*
 			 * We discovered the size of the shm segment, so
 			 * break out of here and fall through to the next
@@ -1810,9 +1810,10 @@ long ksys_shmdt(char __user *shmaddr)
 		/* finding a matching vma now does not alter retval */
 		if ((vma->vm_ops == &shm_vm_ops) &&
 		    ((vma->vm_start - addr)/PAGE_SIZE == vma->vm_pgoff) &&
-		    (vma->vm_file == file))
-			do_vmi_munmap(&vmi, mm, vma->vm_start,
-			      vma->vm_end - vma->vm_start, NULL, false);
+		    (vma->vm_file == file)) {
+			do_vma_munmap(&vmi, vma, vma->vm_start, vma->vm_end,
+				      NULL, false);
+		}
 
 		vma = vma_next(&vmi);
 	}
diff --git a/mm/mmap.c b/mm/mmap.c
index 894017841d5d..408e9cc47333 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -180,9 +180,6 @@ static int check_brk_limits(unsigned long addr, unsigned long len)
 
 	return mlock_future_check(current->mm, current->mm->def_flags, len);
 }
-static int do_brk_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
-			 unsigned long newbrk, unsigned long oldbrk,
-			 struct list_head *uf);
 static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *brkvma,
 		unsigned long addr, unsigned long request, unsigned long flags);
 SYSCALL_DEFINE1(brk, unsigned long, brk)
@@ -236,7 +233,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
 
 	/*
 	 * Always allow shrinking brk.
-	 * do_brk_munmap() may downgrade mmap_lock to read.
+	 * do_vma_munmap() may downgrade mmap_lock to read.
 	 */
 	if (brk <= mm->brk) {
 		int ret;
@@ -248,11 +245,11 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
 			goto out; /* mapping intersects with an existing non-brk vma. */
 		/*
 		 * mm->brk must be protected by write mmap_lock.
-		 * do_brk_munmap() may downgrade the lock,  so update it
-		 * before calling do_brk_munmap().
+		 * do_vma_munmap() may downgrade the lock,  so update it
+		 * before calling do_vma_munmap().
 		 */
 		mm->brk = brk;
-		ret = do_brk_munmap(&vmi, brkvma, newbrk, oldbrk, &uf);
+		ret = do_vma_munmap(&vmi, brkvma, newbrk, oldbrk, &uf, true);
 		if (ret == 1)  {
 			downgraded = true;
 			goto success;
@@ -2951,26 +2948,27 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 }
 
 /*
- * brk_munmap() - Unmap a full or partial vma.
- * @vmi: The vma iterator
- * @vma: The vma to be modified
- * @newbrk: the start of the address to unmap
- * @oldbrk: The end of the address to unmap
+ * do_vma_munmap() - Unmap a full or partial vma.
+ * @vmi: The vma iterator pointing at the vma
+ * @vma: The first vma to be munmapped
+ * @start: the start of the address to unmap
+ * @end: The end of the address to unmap
  * @uf: The userfaultfd list_head
+ * @downgrade: Attempt to downgrade or not
  *
- * Returns: 1 on success.
- * unmaps a partial VMA mapping.  Does not handle alignment, downgrades lock if
- * possible.
+ * Returns: 0 on success and not downgraded, 1 on success and downgraded.
+ * unmaps a VMA mapping when the vma iterator is already in position.
+ * Does not handle alignment.
  */
-static int do_brk_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
-			 unsigned long newbrk, unsigned long oldbrk,
-			 struct list_head *uf)
+int do_vma_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
+		  unsigned long start, unsigned long end,
+		  struct list_head *uf, bool downgrade)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	int ret;
 
-	arch_unmap(mm, newbrk, oldbrk);
-	ret = do_vmi_align_munmap(vmi, vma, mm, newbrk, oldbrk, uf, true);
+	arch_unmap(mm, start, end);
+	ret = do_vmi_align_munmap(vmi, vma, mm, start, end, uf, downgrade);
 	validate_mm_mt(mm);
 	return ret;
 }