Impact: barrier correctness in example launcher I doubt either lguest user will complain about performance. Reported-by: Christoph Hellwig <hch@xxxxxxxxxxxxx> Cc: Jens Axboe <jens.axboe@xxxxxxxxxx> Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx> diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c --- a/Documentation/lguest/lguest.c +++ b/Documentation/lguest/lguest.c @@ -1630,6 +1630,13 @@ static bool service_io(struct device *de } } + /* 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); _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
