This helper does a get_user_pages_fast and if it find pages in the CMA area
it will try to migrate them before taking page reference. This makes sure that
we don't keep non-movable pages (due to page reference count) in the CMA area.
Not able to move pages out of CMA area result in CMA allocation failures.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
---
include/linux/migrate.h | 3 ++
mm/migrate.c | 108 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 111 insertions(+)
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index f2b4abbca55e..d82b35afd2eb 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -286,6 +286,9 @@ static inline int migrate_vma(const struct migrate_vma_ops *ops,
}
#endif /* IS_ENABLED(CONFIG_MIGRATE_VMA_HELPER) */
+extern int get_user_pages_cma_migrate(unsigned long start, int nr_pages, int write,
+ struct page **pages);
+
#endif /* CONFIG_MIGRATION */
#endif /* _LINUX_MIGRATE_H */
diff --git a/mm/migrate.c b/mm/migrate.c
index c27e97b5b69d..c26288d407ae 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -3008,3 +3008,111 @@ int migrate_vma(const struct migrate_vma_ops *ops,
}
EXPORT_SYMBOL(migrate_vma);
#endif /* defined(MIGRATE_VMA_HELPER) */
+
+static struct page *new_non_cma_page(struct page *page, unsigned long private)
+{
+ /*
+ * We want to make sure we allocate the new page from the same node
+ * as the source page.
+ */
+ int nid = page_to_nid(page);
+ gfp_t gfp_mask = GFP_USER | __GFP_THISNODE;
+
+ if (PageHighMem(page))
+ gfp_mask |= __GFP_HIGHMEM;
+
+ if (PageHuge(page)) {
+
+ struct hstate *h = page_hstate(page);
+ /*
+ * We don't want to dequeue from the pool because pool pages will
+ * mostly be from the CMA region.
+ */
+ return alloc_migrate_huge_page(h, gfp_mask, nid, NULL);
+
+ } else if (PageTransHuge(page)) {
+ struct page *thp;
+ gfp_t thp_gfpmask = GFP_TRANSHUGE | __GFP_THISNODE;
+
+ /*
+ * Remove the movable mask so that we don't allocate from
+ * CMA area again.
+ */
+ thp_gfpmask &= ~__GFP_MOVABLE;
+ thp = __alloc_pages_node(nid, thp_gfpmask, HPAGE_PMD_ORDER);
+ if (!thp)
+ return NULL;
+ prep_transhuge_page(thp);
+ return thp;
+ }
+
+ return __alloc_pages_node(nid, gfp_mask, 0);
+}
+
+int get_user_pages_cma_migrate(unsigned long start, int nr_pages, int write,
+ struct page **pages)
+{
+ int i, ret;
+ bool drain_allow = true;
+ bool migrate_allow = true;
+ LIST_HEAD(cma_page_list);
+
+get_user_again:
+ ret = get_user_pages_fast(start, nr_pages, write, pages);
+ if (ret <= 0)
+ return ret;
+
+ for (i = 0; i < ret; ++i) {
+ /*
+ * If we get a page from the CMA zone, since we are going to
+ * be pinning these entries, we might as well move them out
+ * of the CMA zone if possible.
+ */
+ if (is_migrate_cma_page(pages[i]) && migrate_allow) {
+ if (PageHuge(pages[i]))
+ isolate_huge_page(pages[i], &cma_page_list);
+ else {
+ struct page *head = compound_head(pages[i]);
+
+ if (!PageLRU(head) && drain_allow) {
+ lru_add_drain_all();
+ drain_allow = false;
+ }
+
+ if (!isolate_lru_page(head)) {
+ list_add_tail(&head->lru, &cma_page_list);
+ mod_node_page_state(page_pgdat(head),
+ NR_ISOLATED_ANON +
+ page_is_file_cache(head),
+ hpage_nr_pages(head));
+ }
+ }
+ }
+ }
+ if (!list_empty(&cma_page_list)) {
+ /*
+ * drop the above get_user_pages reference.
+ */
+ for (i = 0; i < ret; ++i)
+ put_page(pages[i]);
+
+ if (migrate_pages(&cma_page_list, new_non_cma_page,
+ NULL, 0, MIGRATE_SYNC, MR_CONTIG_RANGE)) {
+ /*
+ * some of the pages failed migration. Do get_user_pages
+ * without migration.
+ */
+ migrate_allow = false;
+
+ if (!list_empty(&cma_page_list))
+ putback_movable_pages(&cma_page_list);
+ }
+ /*
+ * We did migrate all the pages, Try to get the page references again
+ * migrating any new CMA pages which we failed to isolate earlier.
+ */
+ drain_allow = true;
+ goto get_user_again;
+ }
+ return ret;
+}
--
2.17.1
