Gitweb: http://git.kernel.org/linus/d1881d3192a3d3e8dc4f255b03187f4c36cb0617
Commit: d1881d3192a3d3e8dc4f255b03187f4c36cb0617
Parent: df1693abc42e34bbc4351e179dbe66c28a94efb8
Author: Rusty Russell <rusty@rustcorp.com.au>
AuthorDate: Mon Mar 30 21:55:25 2009 -0600
Committer: Rusty Russell <rusty@rustcorp.com.au>
CommitDate: Mon Mar 30 21:55:26 2009 +1030
lguest: barrier me harder
Impact: barrier correctness in example launcher
I doubt either lguest user will complain about performance.
Reported-by: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
Documentation/lguest/lguest.c | 7 +++++++
1 files changed, 7 insertions(+), 0 deletions(-)
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index f2dbbf3..d36fcc0 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);
--
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