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Re: [Qemu-devel] [PATCH v20 02/15] block: Introduce op_blockers to Block


From: Stefan Hajnoczi
Subject: Re: [Qemu-devel] [PATCH v20 02/15] block: Introduce op_blockers to BlockDriverState
Date: Wed, 21 May 2014 14:28:16 +0200
User-agent: Mutt/1.5.23 (2014-03-12)

On Tue, May 20, 2014 at 02:04:27PM +0800, Fam Zheng wrote:
> BlockDriverState.op_blockers is an array of lists with BLOCK_OP_TYPE_MAX
> elements. Each list is a list of blockers of an operation type
> (BlockOpType), that marks this BDS as currently blocked for a certain
> type of operation with reason errors stored in the list. The rule of
> usage is:
> 
>  * BDS user who wants to take an operation should check if there's any
>    blocker of the type with bdrv_op_is_blocked().
> 
>  * BDS user who wants to block certain types of operation, should call
>    bdrv_op_block (or bdrv_op_block_all to block all types of operations,
>    which is similar to the existing bdrv_set_in_use()).
> 
>  * A blocker is only referenced by op_blockers, so the lifecycle is
>    managed by caller, and shouldn't be lost until unblock, so typically
>    a caller does these:
> 
>    - Allocate a blocker with error_setg or similar, call bdrv_op_block()
>      to block some operations.
>    - Hold the blocker, do his job.
>    - Unblock operations that it blocked, with the same reason pointer
>      passed to bdrv_op_unblock().
>    - Release the blocker with error_free().
> 
> Signed-off-by: Fam Zheng <address@hidden>
> Reviewed-by: Benoit Canet <address@hidden>
> Reviewed-by: Jeff Cody <address@hidden>
> ---
>  block.c                   | 76 
> +++++++++++++++++++++++++++++++++++++++++++++++
>  include/block/block.h     |  7 +++++
>  include/block/block_int.h |  5 ++++
>  3 files changed, 88 insertions(+)

Reviewed-by: Stefan Hajnoczi <address@hidden>



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