* [Qemu-devel] when to bdrv_co_flush()?
@ 2014-11-10 2:35 lihuiba
0 siblings, 0 replies; 4+ messages in thread
From: lihuiba @ 2014-11-10 2:35 UTC (permalink / raw)
To: qemu-devel@nongnu.org
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Hi, all
bdrv_co_flush() will flush all cached data to persistent storage, and I'm
wondering whether guest sync() will eventually trigger bdrv_co_flush() be
called.
Intuitively, guest sync() should trigger bdrv_co_flush() in qemu. But simple
grep gave me a negative answer. So I'm wondering why it's not like what I
suspected.
Thanks!
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* [Qemu-devel] when to bdrv_co_flush()?
@ 2014-11-10 4:37 lihuiba
0 siblings, 0 replies; 4+ messages in thread
From: lihuiba @ 2014-11-10 4:37 UTC (permalink / raw)
To: qemu-devel@nongnu.org
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Hi, all
bdrv_co_flush() will flush all cached data to persistent storage, and I'm
wondering whether guest sync() will eventually trigger bdrv_co_flush() be
called.
Intuitively, guest sync() should trigger bdrv_co_flush() in qemu. But simple
grep gave me a negative answer. So I'm wondering why it's not like what I
suspected.
Thanks!
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^ permalink raw reply [flat|nested] 4+ messages in thread
* [Qemu-devel] when to bdrv_co_flush()?
@ 2014-11-10 4:41 lihuiba
2014-11-13 11:36 ` Stefan Hajnoczi
0 siblings, 1 reply; 4+ messages in thread
From: lihuiba @ 2014-11-10 4:41 UTC (permalink / raw)
To: qemu-devel@nongnu.org
[-- Attachment #1: Type: text/plain, Size: 346 bytes --]
Hi, all
bdrv_co_flush() will flush all cached data to persistent storage, and I'm
wondering whether guest sync() will eventually trigger bdrv_co_flush() be
called.
Intuitively, guest sync() should trigger bdrv_co_flush() in qemu. But simple
grep gave me a negative answer. So I'm wondering why it's not like what I
suspected.
Thanks!
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] when to bdrv_co_flush()?
2014-11-10 4:41 [Qemu-devel] when to bdrv_co_flush()? lihuiba
@ 2014-11-13 11:36 ` Stefan Hajnoczi
0 siblings, 0 replies; 4+ messages in thread
From: Stefan Hajnoczi @ 2014-11-13 11:36 UTC (permalink / raw)
To: lihuiba; +Cc: qemu-devel@nongnu.org
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On Mon, Nov 10, 2014 at 12:41:45PM +0800, lihuiba wrote:
> bdrv_co_flush() will flush all cached data to persistent storage, and I'm
> wondering whether guest sync() will eventually trigger bdrv_co_flush() be
> called.
virtio-blk and other emulated storage controllers use bdrv_aio_flush()
to implement disk write cache flush commands.
> Intuitively, guest sync() should trigger bdrv_co_flush() in qemu. But simple
>
> grep gave me a negative answer. So I'm wondering why it's not like what I
>
> suspected.
A correctly configured guest will send cache flush commands, and a
correctly configured QEMU will honor them.
If want help finding the answer, please provide details:
1. Your QEMU command-line
2. Your guest OS version and file system mount options
3. Why you believe bdrv_co_flush() is not being called
Stefan
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