[GFS2] Add gfs2_is_writeback()

This adds a function "gfs2_is_writeback()" along the lines of the
existing "gfs2_is_jdata()" in order to clean up the code and make
the various tests for the inode mode more obvious. It also fixes
the PageChecked() logic where we were resetting the flag too early
in the case of an error path.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 93fa427..1cfd493 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -59,7 +59,6 @@
 static int gfs2_unstuffer_page(struct gfs2_inode *ip, struct buffer_head *dibh,
 			       u64 block, struct page *page)
 {
-	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
 	struct inode *inode = &ip->i_inode;
 	struct buffer_head *bh;
 	int release = 0;
@@ -95,7 +94,7 @@
 	set_buffer_uptodate(bh);
 	if (!gfs2_is_jdata(ip))
 		mark_buffer_dirty(bh);
-	if (sdp->sd_args.ar_data == GFS2_DATA_ORDERED || gfs2_is_jdata(ip))
+	if (!gfs2_is_writeback(ip))
 		gfs2_trans_add_bh(ip->i_gl, bh, 0);
 
 	if (release) {
@@ -879,7 +878,6 @@
 {
 	struct inode *inode = mapping->host;
 	struct gfs2_inode *ip = GFS2_I(inode);
-	struct gfs2_sbd *sdp = GFS2_SB(inode);
 	loff_t from = inode->i_size;
 	unsigned long index = from >> PAGE_CACHE_SHIFT;
 	unsigned offset = from & (PAGE_CACHE_SIZE-1);
@@ -931,7 +929,7 @@
 		err = 0;
 	}
 
-	if (sdp->sd_args.ar_data == GFS2_DATA_ORDERED || gfs2_is_jdata(ip))
+	if (!gfs2_is_writeback(ip))
 		gfs2_trans_add_bh(ip->i_gl, bh, 0);
 
 	zero_user_page(page, offset, length, KM_USER0);