fs: move I_DIRTY_INODE to fs.h

And use it in a few more places rather than opencoding the values.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 620be05..cf5c7f3 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -800,7 +800,7 @@ static void gfs2_dirty_inode(struct inode *inode, int flags)
 	int need_endtrans = 0;
 	int ret;
 
-	if (!(flags & (I_DIRTY_DATASYNC|I_DIRTY_SYNC)))
+	if (!(flags & I_DIRTY_INODE))
 		return;
 	if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags)))
 		return;