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Re: [Qemu-devel] [PATCH v2] blockdev: acquire aio_context for bitmap add

From: Eric Blake
Subject: Re: [Qemu-devel] [PATCH v2] blockdev: acquire aio_context for bitmap add/remove
Date: Tue, 12 Feb 2019 14:16:49 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0

On 2/12/19 2:07 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.

It would be nice to call out which commit id dropped the aio_context
acquisition during bitmap lookup (making it easier to analyze how long
this has broken, and which downstream builds need the backport.

> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1672010
> Reported-By: Aihua Liang <address@hidden>
> ---
>  blockdev.c | 26 ++++++++++++++++++++------
>  1 file changed, 20 insertions(+), 6 deletions(-)

Reviewed-by: Eric Blake <address@hidden>

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

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