ceph: use __page_cache_alloc and add_to_page_cache_lru

Following Nick Piggin patches in btrfs, pagecache pages should be
allocated with __page_cache_alloc, so they obey pagecache memory
policies.

Also, using add_to_page_cache_lru instead of using a private
pagevec where applicable.

Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index 2845422..8938934 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -641,7 +641,7 @@
 			return -ENOMEM;
 		err = -ENOMEM;
 		for (i = 0; i < nr_pages; i++) {
-			pages[i] = alloc_page(GFP_NOFS);
+			pages[i] = __page_cache_alloc(GFP_NOFS);
 			if (!pages[i]) {
 				nr_pages = i;
 				goto out;