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Re: [Qemu-devel] [PATCH v4 1/1] blockdev: acquire aio_context for bitmap

From: Eric Blake
Subject: Re: [Qemu-devel] [PATCH v4 1/1] blockdev: acquire aio_context for bitmap add/remove
Date: Mon, 18 Feb 2019 15:55:51 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0

On 2/18/19 3:42 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>
> ---
>  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
>      }

Your scripts are still going haywire. :(

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

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