[PATCH v3 04/23] iommu/pages: Make iommu_put_pages_list() work with high order allocations

[Jason Gunthorpe <jgg@nvidia.com>]

alloc_pages_node(, order) needs to be paired with __free_pages(, order) to
free all the allocated pages. For order != 0 the return from
alloc_pages_node() is just a page list, it hasn't been formed into a
folio.

However iommu_put_pages_list() just calls put_page() on the head page of
an allocation, which will end up leaking the tail pages if order != 0.

Fix this by using __GFP_COMP to create a high order folio and then always
use put_page() to free the full high order folio.

__iommu_free_account() can get the order of the allocation via
folio_order(), which corrects the accounting of high order allocations in
iommu_put_pages_list(). This is the same technique slub uses.

As far as I can tell, none of the places using high order allocations are
also using the free list, so this not a current bug.

Fixes: 06c375053cef ("iommu/vt-d: add wrapper functions for page allocations")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/iommu/iommu-pages.h | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/iommu-pages.h b/drivers/iommu/iommu-pages.h
index 0ca2437989a0e1..26b91940bdc146 100644
--- a/drivers/iommu/iommu-pages.h
+++ b/drivers/iommu/iommu-pages.h
@@ -38,8 +38,9 @@ static inline void __iommu_alloc_account(struct page *page, int order)
  * @page: head struct page of the page.
  * @order: order of the page
  */
-static inline void __iommu_free_account(struct page *page, int order)
+static inline void __iommu_free_account(struct page *page)
 {
+	unsigned int order = folio_order(page_folio(page));
 	const long pgcnt = 1l << order;
 
 	mod_node_page_state(page_pgdat(page), NR_IOMMU_PAGES, -pgcnt);
@@ -57,7 +58,8 @@ static inline void __iommu_free_account(struct page *page, int order)
  */
 static inline void *iommu_alloc_pages_node(int nid, gfp_t gfp, int order)
 {
-	struct page *page = alloc_pages_node(nid, gfp | __GFP_ZERO, order);
+	struct page *page =
+		alloc_pages_node(nid, gfp | __GFP_ZERO | __GFP_COMP, order);
 
 	if (unlikely(!page))
 		return NULL;
@@ -115,8 +117,8 @@ static inline void iommu_free_pages(void *virt, int order)
 		return;
 
 	page = virt_to_page(virt);
-	__iommu_free_account(page, order);
-	__free_pages(page, order);
+	__iommu_free_account(page);
+	put_page(page);
 }
 
 /**
@@ -143,7 +145,7 @@ static inline void iommu_put_pages_list(struct list_head *page)
 		struct page *p = list_entry(page->prev, struct page, lru);
 
 		list_del(&p->lru);
-		__iommu_free_account(p, 0);
+		__iommu_free_account(p);
 		put_page(p);
 	}
 }
-- 
2.43.0


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