From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: mm/ksm: use vma iterators instead of vma linked list

Remove the use of the linked list for eventual removal.

Link: https://lkml.kernel.org/r/20220426150616.3937571-55-Liam.Howlett@oracle.com
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/ksm.c |   18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

--- a/mm/ksm.c~mm-ksm-use-vma-iterators-instead-of-vma-linked-list
+++ a/mm/ksm.c
@@ -981,11 +981,13 @@ static int unmerge_and_remove_all_rmap_i
 						struct mm_slot, mm_list);
 	spin_unlock(&ksm_mmlist_lock);
 
-	for (mm_slot = ksm_scan.mm_slot;
-			mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) {
+	for (mm_slot = ksm_scan.mm_slot; mm_slot != &ksm_mm_head;
+	     mm_slot = ksm_scan.mm_slot) {
+		VMA_ITERATOR(vmi, mm_slot->mm, 0);
+
 		mm = mm_slot->mm;
 		mmap_read_lock(mm);
-		for (vma = mm->mmap; vma; vma = vma->vm_next) {
+		for_each_vma(vmi, vma) {
 			if (ksm_test_exit(mm))
 				break;
 			if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
@@ -2232,6 +2234,7 @@ static struct rmap_item *scan_get_next_r
 	struct mm_slot *slot;
 	struct vm_area_struct *vma;
 	struct rmap_item *rmap_item;
+	struct vma_iterator vmi;
 	int nid;
 
 	if (list_empty(&ksm_mm_head.mm_list))
@@ -2290,13 +2293,13 @@ next_mm:
 	}
 
 	mm = slot->mm;
+	vma_iter_init(&vmi, mm, ksm_scan.address);
+
 	mmap_read_lock(mm);
 	if (ksm_test_exit(mm))
-		vma = NULL;
-	else
-		vma = find_vma(mm, ksm_scan.address);
+		goto no_vmas;
 
-	for (; vma; vma = vma->vm_next) {
+	for_each_vma(vmi, vma) {
 		if (!(vma->vm_flags & VM_MERGEABLE))
 			continue;
 		if (ksm_scan.address < vma->vm_start)
@@ -2334,6 +2337,7 @@ next_mm:
 	}
 
 	if (ksm_test_exit(mm)) {
+no_vmas:
 		ksm_scan.address = 0;
 		ksm_scan.rmap_list = &slot->rmap_list;
 	}
_