From: "Yan, Zheng" <zyan@redhat.com>
Date: Tue, 23 May 2017 17:18:53 +0800
Subject: ceph: redirty page when writepage_nounlock() skips unwritable page
Git-commit: fa71fefb308532eb5b2e4b38d914d19fc836f73e
Patch-mainline: v4.13-rc1
References: FATE#324714

Ceph needs to flush dirty page in the order in which in which snap
context they belong to. Dirty pages belong to older snap context
should be flushed earlier. if writepage_nounlock() can not flush a
page, it should redirty the page.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Luis Henriques <lhenriques@suse.com>
---
 fs/ceph/addr.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -554,8 +554,9 @@ static int writepage_nounlock(struct pag
 		dout("writepage %p page %p snapc %p not writeable - noop\n",
 		     inode, page, snapc);
 		/* we should only noop if called by kswapd */
-		WARN_ON((current->flags & PF_MEMALLOC) == 0);
+		WARN_ON(!(current->flags & PF_MEMALLOC));
 		ceph_put_snap_context(oldest);
+		redirty_page_for_writepage(wbc, page);
 		goto out;
 	}
 	ceph_put_snap_context(oldest);