[GFS2] fix GFP_KERNEL misuses

There are several places where GFP_KERNEL allocations happen under a glock,
which will result in hangs if we're under memory pressure and go to re-enter the
fs in order to flush stuff out.  This patch changes the culprits to GFS_NOFS to
keep this problem from happening.  Thank you,

Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 88497b0..7aeacbc 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -210,7 +210,7 @@
 	struct page *page;
 	struct bio *bio;
 
-	page = alloc_page(GFP_KERNEL);
+	page = alloc_page(GFP_NOFS);
 	if (unlikely(!page))
 		return -ENOBUFS;
 
@@ -218,7 +218,7 @@
 	ClearPageDirty(page);
 	lock_page(page);
 
-	bio = bio_alloc(GFP_KERNEL, 1);
+	bio = bio_alloc(GFP_NOFS, 1);
 	if (unlikely(!bio)) {
 		__free_page(page);
 		return -ENOBUFS;