Re: [PATCH v5 1/6] ksm: abstract the function try_to_get_old_rmap_item

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On 30.12.22 02:12, yang.yang29@xxxxxxxxxx wrote:
From: xu xin <xu.xin16@xxxxxxxxxx>

A new function try_to_get_old_rmap_item is abstracted from
get_next_rmap_item. This function will be reused by the subsequent
patches about counting ksm_zero_pages.

The patch improves the readability and reusability of KSM code.

Signed-off-by: xu xin <xu.xin16@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Cc: Xuexin Jiang <jiang.xuexin@xxxxxxxxxx>
Reviewed-by: Xiaokai Ran <ran.xiaokai@xxxxxxxxxx>
Reviewed-by: Yang Yang <yang.yang29@xxxxxxxxxx>
---
  mm/ksm.c | 25 +++++++++++++++++++------
  1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index 83e2f74ae7da..5b0a7343ff4a 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2214,23 +2214,36 @@ static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_ite
  	}
  }

-static struct ksm_rmap_item *get_next_rmap_item(struct ksm_mm_slot *mm_slot,
-					    struct ksm_rmap_item **rmap_list,
-					    unsigned long addr)
+static struct ksm_rmap_item *try_to_get_old_rmap_item(unsigned long addr,
+					 struct ksm_rmap_item **rmap_list)
  {
-	struct ksm_rmap_item *rmap_item;
-
  	while (*rmap_list) {
-		rmap_item = *rmap_list;
+		struct ksm_rmap_item *rmap_item = *rmap_list;

Empty line missing.

  		if ((rmap_item->address & PAGE_MASK) == addr)
  			return rmap_item;
  		if (rmap_item->address > addr)
  			break;
  		*rmap_list = rmap_item->rmap_list;
+		/* Running here indicates it's vma has been UNMERGEABLE */

"If we end up here, the VMA is UNMERGEABLE."

Although I am not sure if that is true?

  		remove_rmap_item_from_tree(rmap_item);
  		free_rmap_item(rmap_item);
  	}

+	return NULL;
+}
+
+static struct ksm_rmap_item *get_next_rmap_item(struct ksm_mm_slot *mm_slot,
+					    struct ksm_rmap_item **rmap_list,
+					    unsigned long addr)
+{
+	struct ksm_rmap_item *rmap_item;
+
+	/* lookup if we have a old rmap_item matching the addr*/

I suggest dropping that comment, "try_to_get_old_rmap_item()" is expressive enough.

+	rmap_item = try_to_get_old_rmap_item(addr, rmap_list);
+	if (rmap_item)
+		return rmap_item;
+
+	/* Need to allocate a new rmap_item */

I suggest dropping that comment for the same reason.

  	rmap_item = alloc_rmap_item();
  	if (rmap_item) {
  		/* It has already been zeroed */

--
Thanks,

David / dhildenb





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