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Re: [Qemu-block] [Qemu-devel] [PATCH v2 01/11] block: Add op blocker typ
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From: |
Fam Zheng |
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Subject: |
Re: [Qemu-block] [Qemu-devel] [PATCH v2 01/11] block: Add op blocker type "device IO" |
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Date: |
Thu, 14 May 2015 10:40:59 +0800 |
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User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Wed, 05/13 17:09, Paolo Bonzini wrote:
>
>
> On 13/05/2015 17:02, Fam Zheng wrote:
> >> > For example, SCSI requests can result in many consecutive I/Os:
> >> >
> >> > (1) FUA requests are split in write+flush
> >> >
> >> > (2) adapters that do not use QEMUSGList-based I/O only read 128K at a
> >> > time
> >> >
> >> > (3) WRITE SAME operations are also split in chunks
> >> >
> >> > (4) UNMAP operations process one descriptor at a time
> > I don't understand the point of these examples. If we don't return -EBUSY
> > here,
> > the request will sneak into block/io.c and perhaps break qmp transaction
> > semantics, if it lands between two backups.
>
> It won't, because after blocking DEVICE_IO you will always drain I/O and
> the bdrv_drain will loop until the above are all satisfied.
That's right, I'll drop this patch.
Fam
[Qemu-block] [PATCH v2 03/11] block-backend: Add blk_op_blocker_add_notifier, Fam Zheng, 2015/05/13
[Qemu-block] [PATCH v2 02/11] block: Add op blocker notifier list, Fam Zheng, 2015/05/13
[Qemu-block] [PATCH v2 04/11] virtio-blk: Move complete_request to 'ops' structure, Fam Zheng, 2015/05/13
[Qemu-block] [PATCH v2 05/11] virtio-blk: Don't handle output when there is "device IO" op blocker, Fam Zheng, 2015/05/13
[Qemu-block] [PATCH v2 07/11] blockdev: Block device IO during internal snapshot transaction, Fam Zheng, 2015/05/13
[Qemu-block] [PATCH v2 06/11] nbd-server: Clear "can_read" when "device io" blocker is set, Fam Zheng, 2015/05/13
[Qemu-block] [PATCH v2 08/11] blockdev: Block device IO during external snapshot transaction, Fam Zheng, 2015/05/13
[Qemu-block] [PATCH v2 09/11] blockdev: Block device IO during drive-backup transaction, Fam Zheng, 2015/05/13