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Date: Wed, 7 Jun 2017 20:13:47 +0800
From: Fam Zheng <famz@redhat.com>
Message-ID: <20170607121347.GD4314@lemon.lan>
References: <20170524025235.32190-1-famz@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v3 06/16] backup: Request
 BLK_PERM_AIO_CONTEXT_CHANGE on target
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To: qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-block@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>, Max Reitz <mreitz@redhat.com>

On Wed, 05/24 10:52, Fam Zheng wrote:
> What's done in the source's context change notifier is moving the
> target's context to follow the new one, so we request this permission
> here.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  block/backup.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/backup.c b/block/backup.c
> index a4fb288..546c5c5 100644
> --- a/block/backup.c
> +++ b/block/backup.c
> @@ -636,7 +636,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
>      }
>  
>      /* The target must match the source in size, so no resize here either */
> -    job->target = blk_new(BLK_PERM_WRITE,
> +    job->target = blk_new(BLK_PERM_WRITE | BLK_PERM_AIO_CONTEXT_CHANGE,
>                            BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE |
>                            BLK_PERM_WRITE_UNCHANGED | BLK_PERM_GRAPH_MOD);
>      ret = blk_insert_bs(job->target, target, errp);

Since fc0932fdc we reuse @bs as the backing of @target if sync=none, and this
hunk causes problem: the device's BB probably doesn't permit
BLK_PERM_AIO_CONTEXT_CHANGE.

Still scratching my head on this.

Fam