[XFS] Fix deadlock caused by race between xfs_iunpin marking an inode

dirty, and the same inode being reallocated and reused by create.
The unlock_new_inode and mark_inode_dirty manage to corrupt the
i_state flags and end up leaving I_LOCK|I_NEW set.

SGI Modid: 2.5.x-xfs:slinx:151120a

fs/xfs/xfs_inode.c

@@ -2631,7 +2631,8 @@ xfs_iunpin(
 		if (vp) {
 			struct inode	*inode = LINVFS_GET_IP(vp);
 
-			mark_inode_dirty_sync(inode);
+			if (!(inode->i_state & I_NEW))
+				mark_inode_dirty_sync(inode);
 		}
 
 		wake_up(&ip->i_ipin_wait);