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Date: Sat, 23 May 2015 18:47:00 +0200
From: Max Reitz <mreitz@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v5 10/13] blockdev: Block device IO during
 drive-backup transaction
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To: Fam Zheng <famz@redhat.com>, qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-block@nongnu.org, jcody@redhat.com, armbru@redhat.com, Stefan Hajnoczi <stefanha@redhat.com>, amit.shah@redhat.com, pbonzini@redhat.com

On 20.05.2015 08:16, Fam Zheng wrote:
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>   blockdev.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/blockdev.c b/blockdev.c
> index 923fc90..ae52d27 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1575,6 +1575,7 @@ typedef struct DriveBackupState {
>       BlockDriverState *bs;
>       AioContext *aio_context;
>       BlockJob *job;
> +    Error *blocker;
>   } DriveBackupState;
>   
>   static void drive_backup_prepare(BlkTransactionState *common, Error **errp)
> @@ -1599,6 +1600,9 @@ static void drive_backup_prepare(BlkTransactionState *common, Error **errp)
>       state->aio_context = bdrv_get_aio_context(bs);
>       aio_context_acquire(state->aio_context);
>   
> +    state->bs = bs;
> +    error_setg(&state->blocker, "drive-backup in progress");
> +    bdrv_op_block(bs, BLOCK_OP_TYPE_DEVICE_IO, state->blocker);
>       qmp_drive_backup(backup->device, backup->target,
>                        backup->has_format, backup->format,
>                        backup->sync,
> @@ -1613,7 +1617,6 @@ static void drive_backup_prepare(BlkTransactionState *common, Error **errp)
>           return;
>       }
>   
> -    state->bs = bs;
>       state->job = state->bs->job;
>   }

Okay, pulling that up works here, because drive_backup_abort() checks 
that bs->job is set, and that bs->job == state->job (which cannot be 
true if qmp_drive_backup() failed).

Reviewed-by: Max Reitz <mreitz@redhat.com>

> @@ -1632,6 +1635,10 @@ static void drive_backup_clean(BlkTransactionState *common)
>   {
>       DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
>   
> +    if (state->bs) {
> +        bdrv_op_unblock(state->bs, BLOCK_OP_TYPE_DEVICE_IO, state->blocker);
> +        error_free(state->blocker);
> +    }
>       if (state->aio_context) {
>           aio_context_release(state->aio_context);
>       }