From: Rusty Russell Date: Tue, 31 Mar 2009 03:55:25 +0000 (-0600) Subject: lguest: barrier me harder X-Git-Tag: firefly_0821_release~15180^2 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=d1881d3192a3d3e8dc4f255b03187f4c36cb0617;p=firefly-linux-kernel-4.4.55.git lguest: barrier me harder Impact: barrier correctness in example launcher I doubt either lguest user will complain about performance. Reported-by: Christoph Hellwig Cc: Jens Axboe Signed-off-by: Rusty Russell --- diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c index f2dbbf3bdeab..d36fcc0f2715 100644 --- a/Documentation/lguest/lguest.c +++ b/Documentation/lguest/lguest.c @@ -1630,6 +1630,13 @@ static bool service_io(struct device *dev) } } + /* OK, so we noted that it was pretty poor to use an fdatasync as a + * barrier. But Christoph Hellwig points out that we need a sync + * *afterwards* as well: "Barriers specify no reordering to the front + * or the back." And Jens Axboe confirmed it, so here we are: */ + if (out->type & VIRTIO_BLK_T_BARRIER) + fdatasync(vblk->fd); + /* We can't trigger an IRQ, because we're not the Launcher. It does * that when we tell it we're done. */ add_used(dev->vq, head, wlen);