iommu/amd: Use put_pages_list

page->freelist is for the use of slab.  We already have the ability
to free a list of pages in the core mm, but it requires the use of a
list_head and for the pages to be chained together through page->lru.
Switch the AMD IOMMU code over to using free_pages_list().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
[rm: split from original patch, cosmetic tweaks]
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/73af128f651aaa1f38f69e586c66765a88ad2de0.1639753638.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: Matthew Wilcox (Oracle)

drivers/iommu/amd/io_pgtable.c

@@ -74,26 +74,14 @@ static u64 *first_pte_l7(u64 *pte, unsigned long *page_size,
  *
  ****************************************************************************/
 
-static void free_page_list(struct page *freelist)
-{
-	while (freelist != NULL) {
-		unsigned long p = (unsigned long)page_address(freelist);
-
-		freelist = freelist->freelist;
-		free_page(p);
-	}
-}
-
-static struct page *free_pt_page(u64 *pt, struct page *freelist)
+static void free_pt_page(u64 *pt, struct list_head *freelist)
 {
 	struct page *p = virt_to_page(pt);
 
-	p->freelist = freelist;
-
-	return p;
+	list_add_tail(&p->lru, freelist);
 }
 
-static struct page *free_pt_lvl(u64 *pt, struct page *freelist, int lvl)
+static void free_pt_lvl(u64 *pt, struct list_head *freelist, int lvl)
 {
 	u64 *p;
 	int i;
@@ -114,22 +102,22 @@ static struct page *free_pt_lvl(u64 *pt, struct page *freelist, int lvl)
 		 */
 		p = IOMMU_PTE_PAGE(pt[i]);
 		if (lvl > 2)
-			freelist = free_pt_lvl(p, freelist, lvl - 1);
+			free_pt_lvl(p, freelist, lvl - 1);
 		else
-			freelist = free_pt_page(p, freelist);
+			free_pt_page(p, freelist);
 	}
 
-	return free_pt_page(pt, freelist);
+	free_pt_page(pt, freelist);
 }
 
-static struct page *free_sub_pt(u64 *root, int mode, struct page *freelist)
+static void free_sub_pt(u64 *root, int mode, struct list_head *freelist)
 {
 	switch (mode) {
 	case PAGE_MODE_NONE:
 	case PAGE_MODE_7_LEVEL:
 		break;
 	case PAGE_MODE_1_LEVEL:
-		freelist = free_pt_page(root, freelist);
+		free_pt_page(root, freelist);
 		break;
 	case PAGE_MODE_2_LEVEL:
 	case PAGE_MODE_3_LEVEL:
@@ -141,8 +129,6 @@ static struct page *free_sub_pt(u64 *root, int mode, struct page *freelist)
 	default:
 		BUG();
 	}
-
-	return freelist;
 }
 
 void amd_iommu_domain_set_pgtable(struct protection_domain *domain,
@@ -350,7 +336,7 @@ static u64 *fetch_pte(struct amd_io_pgtable *pgtable,
 	return pte;
 }
 
-static struct page *free_clear_pte(u64 *pte, u64 pteval, struct page *freelist)
+static void free_clear_pte(u64 *pte, u64 pteval, struct list_head *freelist)
 {
 	u64 *pt;
 	int mode;
@@ -361,12 +347,12 @@ static struct page *free_clear_pte(u64 *pte, u64 pteval, struct page *freelist)
 	}
 
 	if (!IOMMU_PTE_PRESENT(pteval))
-		return freelist;
+		return;
 
 	pt   = IOMMU_PTE_PAGE(pteval);
 	mode = IOMMU_PTE_MODE(pteval);
 
-	return free_sub_pt(pt, mode, freelist);
+	free_sub_pt(pt, mode, freelist);
 }
 
 /*
@@ -380,7 +366,7 @@ static int iommu_v1_map_page(struct io_pgtable_ops *ops, unsigned long iova,
 			  phys_addr_t paddr, size_t size, int prot, gfp_t gfp)
 {
 	struct protection_domain *dom = io_pgtable_ops_to_domain(ops);
-	struct page *freelist = NULL;
+	LIST_HEAD(freelist);
 	bool updated = false;
 	u64 __pte, *pte;
 	int ret, i, count;
@@ -400,9 +386,9 @@ static int iommu_v1_map_page(struct io_pgtable_ops *ops, unsigned long iova,
 		goto out;
 
 	for (i = 0; i < count; ++i)
-		freelist = free_clear_pte(&pte[i], pte[i], freelist);
+		free_clear_pte(&pte[i], pte[i], &freelist);
 
-	if (freelist != NULL)
+	if (!list_empty(&freelist))
 		updated = true;
 
 	if (count > 1) {
@@ -437,7 +423,7 @@ static int iommu_v1_map_page(struct io_pgtable_ops *ops, unsigned long iova,
 	}
 
 	/* Everything flushed out, free pages now */
-	free_page_list(freelist);
+	put_pages_list(&freelist);
 
 	return ret;
 }
@@ -499,7 +485,7 @@ static void v1_free_pgtable(struct io_pgtable *iop)
 {
 	struct amd_io_pgtable *pgtable = container_of(iop, struct amd_io_pgtable, iop);
 	struct protection_domain *dom;
-	struct page *freelist = NULL;
+	LIST_HEAD(freelist);
 
 	if (pgtable->mode == PAGE_MODE_NONE)
 		return;
@@ -516,9 +502,9 @@ static void v1_free_pgtable(struct io_pgtable *iop)
 	BUG_ON(pgtable->mode < PAGE_MODE_NONE ||
 	       pgtable->mode > PAGE_MODE_6_LEVEL);
 
-	freelist = free_sub_pt(pgtable->root, pgtable->mode, freelist);
+	free_sub_pt(pgtable->root, pgtable->mode, &freelist);
 
-	free_page_list(freelist);
+	put_pages_list(&freelist);
 }
 
 static struct io_pgtable *v1_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)