[Patch v3 4/4] mm/mremap: use pmd_addr_end to simplify the calculate of extent

[Wei Yang]

The purpose of this code is to calculate the smaller extent in old and
new range. Let's leverage pmd_addr_end() to do the calculation.

Hope this would make the code easier to read.

Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx>
---
 mm/mremap.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/mm/mremap.c b/mm/mremap.c
index f5f17d050617..76e7fdf567c3 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -237,11 +237,12 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
 		unsigned long new_addr, unsigned long len,
 		bool need_rmap_locks)
 {
-	unsigned long extent, next, old_end;
+	unsigned long extent, old_next, new_next, old_end, new_end;
 	struct mmu_notifier_range range;
 	pmd_t *old_pmd, *new_pmd;
 
 	old_end = old_addr + len;
+	new_end = new_addr + len;
 	flush_cache_range(vma, old_addr, old_end);
 
 	mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, vma->vm_mm,
@@ -250,14 +251,11 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
 
 	for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 		cond_resched();
-		next = (old_addr + PMD_SIZE) & PMD_MASK;
-		/* even if next overflowed, extent below will be ok */
-		extent = next - old_addr;
-		if (extent > old_end - old_addr)
-			extent = old_end - old_addr;
-		next = (new_addr + PMD_SIZE) & PMD_MASK;
-		if (extent > next - new_addr)
-			extent = next - new_addr;
+
+		old_next = pmd_addr_end(old_addr, old_end);
+		new_next = pmd_addr_end(new_addr, new_end);
+		extent = min((old_next - old_addr), (new_next - new_addr));
+
 		old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 		if (!old_pmd)
 			continue;
-- 
2.20.1 (Apple Git-117)