Re: [Qemu-devel] [PULL 3/3] blockdev: acquire aio_context for bitmap add/remove

[Eric Blake]

On 2/13/19 5:49 PM, John Snow wrote:
> When bitmaps are persistent, they may incur a disk read or write when bitmaps
> are added or removed. For configurations like virtio-dataplane, failing to
> acquire this lock will abort QEMU when disk IO occurs.
> 
> We used to acquire aio_context as part of the bitmap lookup, so re-introduce
> the lock for just the cases that have an IO penalty. Commit 2119882c removed
> these locks, and I failed to notice this when we committed fd5ae4cc, so this
> has been broken since persistent bitmaps were introduced.
> 
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1672010
> Reported-By: Aihua Liang <address@hidden>
> Signed-off-by: John Snow <address@hidden>
> Reviewed-by: Eric Blake <address@hidden>
> Message-id: address@hidden
> Signed-off-by: John Snow <address@hidden>
> ---
>  blockdev.c | 26 ++++++++++++++++++++------
>  1 file changed, 20 insertions(+), 6 deletions(-)

>      bitmap = bdrv_create_dirty_bitmap(bs, granularity, name, errp);
>      if (bitmap == NULL) {
> -        return;
> +        goto out

Embarrassing enough that I missed this syntax error in spite of my R-b,
but even more embarrassing that we have a pull request that has
obviously not been compiled. At least patchew called it out.

We're not in enough of a rush to need this PR to land this week, so I
won't try to post a v2 on your behalf, but will instead wait for your
return next week.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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