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Re: [Qemu-devel] [PATCH 1/2] block: add the support for draining the thr
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH 1/2] block: add the support for draining the throttled request queue |
Date: |
Fri, 24 Feb 2012 08:49:03 +0000 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, Feb 20, 2012 at 12:50:30PM +0800, address@hidden wrote:
> From: Zhi Yong Wu <address@hidden>
>
> If one guest has multiple disks with enabling I/O throttling function
> separately, when draining activities are done, some requests maybe are in the
> throttled queue; So we need to restart them at first.
>
> Moreover, when only one disk need to be drained such as hotplug out, if
> another disk still has some requests in its throttled queue, these request
> should not be effected.
>
> Signed-off-by: Zhi Yong Wu <address@hidden>
> ---
> block.c | 29 ++++++++++++++++++++++-------
> block_int.h | 1 +
> 2 files changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/block.c b/block.c
> index ae297bb..f78df78 100644
> --- a/block.c
> +++ b/block.c
> @@ -853,25 +853,40 @@ void bdrv_close_all(void)
> }
> }
>
> -/*
> - * Wait for pending requests to complete across all BlockDriverStates
> - *
> - * This function does not flush data to disk, use bdrv_flush_all() for that
> - * after calling this function.
> - */
> -void bdrv_drain_all(void)
> +void bdrv_drain_request(BlockDriverState *throttled_bs)
> {
> BlockDriverState *bs;
>
> + QTAILQ_FOREACH(bs, &bdrv_states, list) {
> + if (throttled_bs && throttled_bs != bs) {
> + continue;
> + }
> + qemu_co_queue_restart_all(&bs->throttled_reqs);
> + }
> +
> qemu_aio_flush();
Since I/O throttling is still enabled, the restarted requests could
enqueue again if they exceed the limit. We could still hit the assert.
If the semantics of bdrv_drain_request() are that no requests are
pending when it returns then we need a loop here.
BTW bdrv_drain() would be a shorter name for this function.
Stefan