[PATCH v3 06/15] mm: Remove re-walk from mmap_region()

["Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>]

Using vma_iter_set() will reset the tree and cause a re-walk.  Use
vmi_iter_config() to set the write to a sub-set of the range.  Change
the file case to also use vmi_iter_config() so that the end is correctly
set.

Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
---
 mm/internal.h |  8 ++++++++
 mm/mmap.c     | 15 ++++++++++-----
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 7d11ebe5d11c..c5ba08f55deb 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1041,6 +1041,14 @@ static inline bool vma_soft_dirty_enabled(struct vm_area_struct *vma)
 	return !(vma->vm_flags & VM_SOFTDIRTY);
 }
 
+static inline void vma_iter_config(struct vma_iterator *vmi,
+		unsigned long index, unsigned long last)
+{
+	MAS_BUG_ON(&vmi->mas, vmi->mas.node != MAS_START &&
+		   (vmi->mas.index > index || vmi->mas.last < index));
+	__mas_set_range(&vmi->mas, index, last - 1);
+}
+
 /*
  * VMA Iterator functions shared between nommu and mmap
  */
diff --git a/mm/mmap.c b/mm/mmap.c
index d4056d1de7fa..f518e4c70a7b 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2675,8 +2675,11 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 
 	next = vma_next(&vmi);
 	prev = vma_prev(&vmi);
-	if (vm_flags & VM_SPECIAL)
+	if (vm_flags & VM_SPECIAL) {
+		if (prev)
+			vma_iter_next_range(&vmi);
 		goto cannot_expand;
+	}
 
 	/* Attempt to expand an old mapping */
 	/* Check next */
@@ -2697,6 +2700,8 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 		merge_start = prev->vm_start;
 		vma = prev;
 		vm_pgoff = prev->vm_pgoff;
+	} else if (prev) {
+		vma_iter_next_range(&vmi);
 	}
 
 
@@ -2707,9 +2712,9 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 		goto expanded;
 	}
 
+	if (vma == prev)
+		vma_iter_set(&vmi, addr);
 cannot_expand:
-	if (prev)
-		vma_iter_next_range(&vmi);
 
 	/*
 	 * Determine the object being mapped and call the appropriate
@@ -2722,7 +2727,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 		goto unacct_error;
 	}
 
-	vma_iter_set(&vmi, addr);
+	vma_iter_config(&vmi, addr, end);
 	vma->vm_start = addr;
 	vma->vm_end = end;
 	vm_flags_init(vma, vm_flags);
@@ -2749,7 +2754,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 		if (WARN_ON((addr != vma->vm_start)))
 			goto close_and_free_vma;
 
-		vma_iter_set(&vmi, addr);
+		vma_iter_config(&vmi, addr, end);
 		/*
 		 * If vm_flags changed after call_mmap(), we should try merge
 		 * vma again as we may succeed this time.
-- 
2.39.2