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author | Rusty Russell <rusty@rustcorp.com.au> | 2009-03-30 21:55:25 -0600 |
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committer | Rusty Russell <rusty@rustcorp.com.au> | 2009-03-30 21:55:26 +1030 |
commit | d1881d3192a3d3e8dc4f255b03187f4c36cb0617 (patch) | |
tree | 851f74b371136a85226d4180f84b4904762abb0d /Documentation/lguest | |
parent | df1693abc42e34bbc4351e179dbe66c28a94efb8 (diff) | |
download | kernel_samsung_crespo-d1881d3192a3d3e8dc4f255b03187f4c36cb0617.zip kernel_samsung_crespo-d1881d3192a3d3e8dc4f255b03187f4c36cb0617.tar.gz kernel_samsung_crespo-d1881d3192a3d3e8dc4f255b03187f4c36cb0617.tar.bz2 |
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>
Diffstat (limited to 'Documentation/lguest')
-rw-r--r-- | 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); |