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

From: John Snow
Subject: Re: [Qemu-devel] [PATCH v2] blockdev: acquire aio_context for bitmap add/remove
Date: Tue, 12 Feb 2019 16:37:06 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0

On 2/12/19 3:16 PM, Eric Blake wrote:
> 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.

OK, I will amend this.

Looks like:

commit 2119882c7eb7e2c612b24fc0c8d86f5887d6f1c3
Author: Paolo Bonzini <address@hidden>
Date:   Mon Jun 5 14:39:03 2017 +0200

since 2.10.

>> 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>

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