1 files changed, 43 insertions, 0 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 4d1e120536eb..8e101b74df71 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1651,6 +1651,45 @@ static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long add
 }
 
 /**
+ * replace_cma_page() - migrate page out of CMA page blocks
+ * @page:	source page to be migrated
+ *
+ * Returns either the old page (if migration was not possible) or the pointer
+ * to the newly allocated page (with additional reference taken).
+ *
+ * get_user_pages() might take a reference to a page for a long period of time,
+ * what prevent such page from migration. This is fatal to the preffered usage
+ * pattern of CMA pageblocks. This function replaces the given user page with
+ * a new one allocated from NON-MOVABLE pageblock, so locking CMA page can be
+ * avoided.
+ */
+static inline struct page *migrate_replace_cma_page(struct page *page)
+{
+	struct page *newpage = alloc_page(GFP_HIGHUSER);
+
+	if (!newpage)
+		goto out;
+
+	/*
+	 * Take additional reference to the new page to ensure it won't get
+	 * freed after migration procedure end.
+	 */
+	get_page_foll(newpage);
+
+	if (migrate_replace_page(page, newpage) == 0)
+		return newpage;
+
+	put_page(newpage);
+	__free_page(newpage);
+out:
+	/*
+	 * Migration errors in case of get_user_pages() might not
+	 * be fatal to CMA itself, so better don't fail here.
+	 */
+	return page;
+}
+
+/**
  * __get_user_pages() - pin user pages in memory
  * @tsk:	task_struct of target task
  * @mm:		mm_struct of target mm
@@ -1885,6 +1924,10 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 			}
 			if (IS_ERR(page))
 				return i ? i : PTR_ERR(page);
+
+			if ((gup_flags & FOLL_DURABLE) && is_cma_page(page))
+				page = migrate_replace_cma_page(page);
+
 			if (pages) {
 				pages[i] = page;