diff mbox series

[4/5] mm/mremap: calculate extent in one place

Message ID 20200117232254.2792-5-richardw.yang@linux.intel.com (mailing list archive)
State New, archived
Headers show
Series mm/mremap.c: cleanup move_page_tables() a little | expand

Commit Message

Wei Yang Jan. 17, 2020, 11:22 p.m. UTC 
Page tables is moved on the base of PMD. This requires both source
and destination range should meet the requirement.

Current code works well since move_huge_pmd() and move_normal_pmd()
would check old_addr and new_addr again. And then return to move_ptes()
if the either of them is not aligned.

In stead of calculating the extent separately, it is better to calculate
in one place, so we know it is not necessary to try move pmd. By doing
so, the logic seems a little clear.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
---
 mm/mremap.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)
diff mbox series

Patch

diff --git a/mm/mremap.c b/mm/mremap.c
index a258914f3ee1..37335a10779d 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -240,7 +240,7 @@  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;
 	struct mmu_notifier_range range;
 	pmd_t *old_pmd, *new_pmd;
 
@@ -253,8 +253,9 @@  unsigned long move_page_tables(struct vm_area_struct *vma,
 
 	for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 		cond_resched();
-		next = pmd_addr_end(old_addr, old_end);
-		extent = next - old_addr;
+		old_next = pmd_addr_end(old_addr, old_end);
+		new_next = pmd_addr_end(new_addr, new_addr + len);
+		extent = min((old_next - old_addr), (new_next - new_addr));
 		old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 		if (!old_pmd)
 			continue;
@@ -298,9 +299,6 @@  unsigned long move_page_tables(struct vm_area_struct *vma,
 
 		if (pte_alloc(new_vma->vm_mm, new_pmd))
 			break;
-		next = pmd_addr_end(new_addr, new_addr + len);
-		if (extent > next - new_addr)
-			extent = next - new_addr;
 		move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma,
 			  new_pmd, new_addr, need_rmap_locks);
 	}