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lguest: barrier me harder

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Impact: barrier correctness in example launcher

I doubt either lguest user will complain about performance.

Reported-by: Christoph Hellwig <[email protected]>
Cc: Jens Axboe <[email protected]>
Signed-off-by: Rusty Russell <[email protected]>
This commit is contained in:
Rusty Russell 2009-03-30 21:55:25 -06:00
commit d1881d3192
1 changed files with 7 additions and 0 deletions
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7
Documentation/lguest/lguest.c
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@ -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);