fs: fuse: Workaround for CMA migration

    The FUSE file system may hold references to pages for long
    periods of time, preventing migration from occuring. If a CMA
    page is used here, CMA allocations may fail. Work around this
    by swapping out a CMA page for a non-CMA page when working with
    the FUSE file system.

    Change-Id: Id763ea833ee125c8732ae3759ec9e20d94aa8424
    Signed-off-by: Laura Abbott <lauraa@codeaurora.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 65eb03f..18c215c 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -660,6 +660,41 @@ static int fuse_readpages_fill(void *_data, struct page *page)
 			return PTR_ERR(req);
 		}
 	}
+#ifdef CONFIG_CMA
+	if (get_pageblock_migratetype(page) == MIGRATE_CMA) {
+		struct page *oldpage = page, *newpage;
+		int err;
+
+		/* make sure that old page is not free in-between the calls */
+		page_cache_get(oldpage);
+
+		newpage = alloc_page(GFP_HIGHUSER);
+		if (!newpage) {
+			page_cache_release(oldpage);
+			return -ENOMEM;
+		}
+
+		err = replace_page_cache_page(oldpage, newpage, GFP_KERNEL);
+		if (err) {
+			__free_page(newpage);
+			page_cache_release(oldpage);
+			return err;
+		}
+
+		/*
+		 * Decrement the count on new page to make page cache the only
+		 * owner of it
+		 */
+		lock_page(newpage);
+		put_page(newpage);
+
+		/* finally release the old page and swap pointers */
+		unlock_page(oldpage);
+		page_cache_release(oldpage);
+		page = newpage;
+	}
+#endif
+
 	page_cache_get(page);
 	req->pages[req->num_pages] = page;
 	req->num_pages++;