[PATCH 23/28] mm/mmap: Add do_mas_munmap() and wraper for __do_munmap()

[Liam R. Howlett]

To avoid extra tree work, it is necessary to support passing in a maple state
to key functions.  Start this work with __do_munmap().

Signed-off-by: Liam R. Howlett <Liam.Howlett at Oracle.com>
---
 mm/mmap.c | 102 ++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 72 insertions(+), 30 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index b501388c73ebd..4ef32ed2c34dc 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2422,34 +2422,24 @@ static inline int unlock_range(struct vm_area_struct *start,
 
 	return count;
 }
-/* Munmap is split into 2 main parts -- this part which finds
- * what needs doing, and the areas themselves, which do the
- * work.  This now handles partial unmappings.
- * Jeremy Fitzhardinge <jeremy at goop.org>
+
+/* do_mas_align_munmap() - munmap the aligned region from @start to @end.
+ *
+ * @mas: The maple_state, ideally set up to alter the correct tree location.
+ * @vma: The starting vm_area_struct
+ * @mm: The mm_struct
+ * @start: The aligned start address to munmap.
+ * @end: The aligned end address to munmap.
+ * @uf: The userfaultfd list_head
+ * @downgrade: Set to true to attempt a downwrite of the mmap_sem
+ *
+ *
  */
-int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
-		struct list_head *uf, bool downgrade)
+int do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
+			struct mm_struct *mm, unsigned long start,
+			unsigned long end, struct list_head *uf, bool downgrade)
 {
-	unsigned long end;
-	struct vm_area_struct *vma, *prev, *last;
-	MA_STATE(mas, &mm->mm_mt, start, start);
-
-	if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
-		return -EINVAL;
-
-	end = start + PAGE_ALIGN(len);
-	if (end == start)
-		return -EINVAL;
-
-	 /* arch_unmap() might do unmaps itself.  */
-	arch_unmap(mm, start, end);
-
-	/* Find the first overlapping VMA */
-	vma = mas_find(&mas, end - 1);
-	if (!vma)
-		return 0;
-
-	mas.last = end - 1;
+	struct vm_area_struct *prev, *last;
 	/* we have start < vma->vm_end  */
 
 	/*
@@ -2474,8 +2464,8 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 			return error;
 		prev = vma;
 		vma = vma_next(mm, prev);
-		mas.index = start;
-		mas_reset(&mas);
+		mas->index = start;
+		mas_reset(mas);
 	} else {
 		prev = vma->vm_prev;
 	}
@@ -2491,7 +2481,7 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 		if (error)
 			return error;
 		vma = vma_next(mm, prev);
-		mas_reset(&mas);
+		mas_reset(mas);
 	}
 
 
@@ -2518,7 +2508,7 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 	 */
 	mm->map_count -= unlock_range(vma, &last, end);
 	/* Drop removed area from the tree */
-	mas_store_gfp(&mas, NULL, GFP_KERNEL);
+	mas_store_gfp(mas, NULL, GFP_KERNEL);
 
 	/* Detach vmas from the MM linked list */
 	vma->vm_prev = NULL;
@@ -2555,6 +2545,58 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 	return downgrade ? 1 : 0;
 }
 
+int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
+		struct list_head *uf, bool downgrade)
+{
+	MA_STATE(mas, &mm->mm_mt, start, start);
+	return do_mas_munmap(&mas, mm, start, len, uf, downgrade);
+}
+
+/*
+ * do_mas_munmap() - munmap a given range.
+ * @mas: The maple state
+ * @mm: The mm_struct
+ * @start: The start address to munmap
+ * @len: The length of the range to munmap
+ * @uf: The userfaultfd list_head
+ * @downgrade: set to true if the user wants to attempt to write_downgrade the
+ * mmap_sem
+ *
+ * This function takes a @mas that is in the correct state to remove the
+ * mapping(s).  The @len will be aligned and any arch_unmap work will be
+ * preformed.
+ */
+int do_mas_munmap(struct ma_state *mas, struct mm_struct *mm,
+		  unsigned long start, size_t len, struct list_head *uf,
+		  bool downgrade)
+{
+	unsigned long end;
+	struct vm_area_struct *vma;
+
+	if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
+		return -EINVAL;
+
+	end = start + PAGE_ALIGN(len);
+	if (end == start)
+		return -EINVAL;
+
+	 /* arch_unmap() might do unmaps itself.  */
+	arch_unmap(mm, start, end);
+
+	/* Find the first overlapping VMA */
+	vma = mas_find(mas, end - 1);
+	if (!vma)
+		return 0;
+
+	mas->last = end - 1;
+	return do_mas_align_munmap(mas, vma, mm, start, end, uf, downgrade);
+}
+/* do_munmap() - Wrapper function for non-maple tree aware do_munmap() calls.
+ * @mm: The mm_struct
+ * @start: The start address to munmap
+ * @len: The length to be munmapped.
+ * @uf: The userfaultfd list_head
+ */
 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 	      struct list_head *uf)
 {
-- 
2.28.0