[PATCH v4 12/13] mm: hugetlb_vmemmap: unify vmemmap range restoration

[Muchun Song]

Restoring an optimized folio and rolling back a partial optimization
both restore a vmemmap range, but the operation is currently implemented
separately in each path.

Use a single range-restoration path for both cases, making rollback an
explicit bounded form of normal restoration.

No functional change intended.

Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Reviewed-by: Lance Yang <lance.yang@xxxxxxxxx>
Reviewed-by: Qi Zheng <qi.zheng@xxxxxxxxx>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
Tested-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
v4:
- Collect Reviewed-by from Oscar Salvador
- Collect Tested-by from Andrew Morton

v3:
- Collect Reviewed-by from Mike Rapoport

v2:
- Collect Reviewed-by from Lance Yang and Qi Zheng
---
 mm/hugetlb_vmemmap.c | 33 ++++++++++++++-------------------
 1 file changed, 14 insertions(+), 19 deletions(-)

diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 359e53302a67..b8c10671d53b 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -287,6 +287,18 @@ static int vmemmap_restore_pte(pte_t *pte, unsigned long addr,
 	return 0;
 }
 
+static inline int vmemmap_restore_range(unsigned long start, unsigned long end,
+		struct list_head *vmemmap_pages, unsigned long flags)
+{
+	struct vmemmap_remap_walk walk = {
+		.remap_pte	= vmemmap_restore_pte,
+		.vmemmap_pages	= vmemmap_pages,
+		.flags		= flags,
+	};
+
+	return vmemmap_remap_range(start, end, &walk);
+}
+
 /**
  * vmemmap_remap_split - split the vmemmap virtual address range [@start, @end)
  *                      backing PMDs of the directmap into PTEs
@@ -348,19 +360,7 @@ static int vmemmap_optimize_folio(const struct folio *folio,
 		return ret;
 
 	end = start + walk.nr_walked * PAGE_SIZE;
-
-	/*
-	 * vmemmap_pages contains pages from the previous vmemmap_remap_range()
-	 * call which failed.  These are pages which were removed from
-	 * the vmemmap. They will be restored in the following call.
-	 */
-	walk = (struct vmemmap_remap_walk) {
-		.remap_pte	= vmemmap_restore_pte,
-		.vmemmap_pages	= vmemmap_pages,
-		.flags		= 0,
-	};
-
-	vmemmap_remap_range(start, end, &walk);
+	vmemmap_restore_range(start, end, vmemmap_pages, 0);
 
 	return ret;
 }
@@ -382,11 +382,6 @@ static int vmemmap_restore_folio(const struct folio *folio, unsigned long flags)
 	unsigned long end = start + folio_vmemmap_size(folio);
 	int ret, nid = folio_nid(folio);
 	LIST_HEAD(vmemmap_pages);
-	struct vmemmap_remap_walk walk = {
-		.remap_pte	= vmemmap_restore_pte,
-		.vmemmap_pages	= &vmemmap_pages,
-		.flags		= flags,
-	};
 
 	start += VMEMMAP_OPTIMIZATION_SIZE;
 	ret = alloc_vmemmap_page_list(&vmemmap_pages, (end - start) / PAGE_SIZE,
@@ -394,7 +389,7 @@ static int vmemmap_restore_folio(const struct folio *folio, unsigned long flags)
 	if (ret)
 		return ret;
 
-	return vmemmap_remap_range(start, end, &walk);
+	return vmemmap_restore_range(start, end, &vmemmap_pages, flags);
 }
 
 static bool vmemmap_optimize_enabled = IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON);
-- 
2.54.0