xen: don't use page->lru for ZONE_DEVICE memory

Commit 9e2369c06c8a18 ("xen: add helpers to allocate unpopulated
memory") introduced usage of ZONE_DEVICE memory for foreign memory
mappings.

Unfortunately this collides with using page->lru for Xen backend
private page caches.

Fix that by using page->zone_device_data instead.

Cc: <stable@vger.kernel.org> # 5.9
Fixes: 9e2369c06c8a18 ("xen: add helpers to allocate unpopulated memory")
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovksy@oracle.com>
Reviewed-by: Jason Andryuk <jandryuk@gmail.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

1 files changed, 58 insertions, 7 deletions

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index e2e42912f241..3729bea0c989 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -813,10 +813,63 @@ int gnttab_alloc_pages(int nr_pages, struct page **pages)
 }
 EXPORT_SYMBOL_GPL(gnttab_alloc_pages);
 
+#ifdef CONFIG_XEN_UNPOPULATED_ALLOC
+static inline void cache_init(struct gnttab_page_cache *cache)
+{
+	cache->pages = NULL;
+}
+
+static inline bool cache_empty(struct gnttab_page_cache *cache)
+{
+	return !cache->pages;
+}
+
+static inline struct page *cache_deq(struct gnttab_page_cache *cache)
+{
+	struct page *page;
+
+	page = cache->pages;
+	cache->pages = page->zone_device_data;
+
+	return page;
+}
+
+static inline void cache_enq(struct gnttab_page_cache *cache, struct page *page)
+{
+	page->zone_device_data = cache->pages;
+	cache->pages = page;
+}
+#else
+static inline void cache_init(struct gnttab_page_cache *cache)
+{
+	INIT_LIST_HEAD(&cache->pages);
+}
+
+static inline bool cache_empty(struct gnttab_page_cache *cache)
+{
+	return list_empty(&cache->pages);
+}
+
+static inline struct page *cache_deq(struct gnttab_page_cache *cache)
+{
+	struct page *page;
+
+	page = list_first_entry(&cache->pages, struct page, lru);
+	list_del(&page->lru);
+
+	return page;
+}
+
+static inline void cache_enq(struct gnttab_page_cache *cache, struct page *page)
+{
+	list_add(&page->lru, &cache->pages);
+}
+#endif
+
 void gnttab_page_cache_init(struct gnttab_page_cache *cache)
 {
 	spin_lock_init(&cache->lock);
-	INIT_LIST_HEAD(&cache->pages);
+	cache_init(cache);
 	cache->num_pages = 0;
 }
 EXPORT_SYMBOL_GPL(gnttab_page_cache_init);
@@ -827,13 +880,12 @@ int gnttab_page_cache_get(struct gnttab_page_cache *cache, struct page **page)
 
 	spin_lock_irqsave(&cache->lock, flags);
 
-	if (list_empty(&cache->pages)) {
+	if (cache_empty(cache)) {
 		spin_unlock_irqrestore(&cache->lock, flags);
 		return gnttab_alloc_pages(1, page);
 	}
 
-	page[0] = list_first_entry(&cache->pages, struct page, lru);
-	list_del(&page[0]->lru);
+	page[0] = cache_deq(cache);
 	cache->num_pages--;
 
 	spin_unlock_irqrestore(&cache->lock, flags);
@@ -851,7 +903,7 @@ void gnttab_page_cache_put(struct gnttab_page_cache *cache, struct page **page,
 	spin_lock_irqsave(&cache->lock, flags);
 
 	for (i = 0; i < num; i++)
-		list_add(&page[i]->lru, &cache->pages);
+		cache_enq(cache, page[i]);
 	cache->num_pages += num;
 
 	spin_unlock_irqrestore(&cache->lock, flags);
@@ -867,8 +919,7 @@ void gnttab_page_cache_shrink(struct gnttab_page_cache *cache, unsigned int num)
 	spin_lock_irqsave(&cache->lock, flags);
 
 	while (cache->num_pages > num) {
-		page[i] = list_first_entry(&cache->pages, struct page, lru);
-		list_del(&page[i]->lru);
+		page[i] = cache_deq(cache);
 		cache->num_pages--;
 		if (++i == ARRAY_SIZE(page)) {
 			spin_unlock_irqrestore(&cache->lock, flags);