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Re: [Qemu-devel] [PATCH 2/2] scsi: add block job opblockers for scsi-blo
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] scsi: add block job opblockers for scsi-block |
Date: |
Mon, 12 Feb 2018 15:00:50 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 |
On 12/02/2018 14:52, Kevin Wolf wrote:
> Am 08.02.2018 um 11:42 hat Paolo Bonzini geschrieben:
>> On 08/02/2018 02:35, Fam Zheng wrote:
>>> On Wed, 02/07 17:36, Paolo Bonzini wrote:
>>>> @@ -2626,6 +2656,36 @@ static void scsi_block_realize(SCSIDevice *dev,
>>>> Error **errp)
>>>>
>>>> scsi_realize(&s->qdev, errp);
>>>> scsi_generic_read_device_identification(&s->qdev);
>>>> +
>>>> + /* For op blockers, due to lack of support for dirty bitmaps. */
>>>> + error_setg(&sb->mirror_source,
>>>> + "scsi-block does not support acting as a mirroring
>>>> source");
>>>> + error_setg(&sb->commit_source,
>>>> + "scsi-block does not support acting as an active commit
>>>> source");
>>>
>>> An alternative way would be adding BLOCK_OP_TYPE_DIRTY_BITMAP. The error
>>> message
>>> will not be as nice but it can be useful for another (blockjob) operation
>>> that
>>> requires dirty bitmap support, or another device that doesn't support dirty
>>> bitmaps. Though there isn't one for now.
>>
>> Yeah, I thought about it. Another possibility is make BLOCK_OP_TYPE_* a
>> bitmask. Then you can easily add a single Error * for multiple
>> blockers, and BLOCK_OP_TYPE_DIRTY_BITMAP can be defined as
>> BLOCK_OP_TYPE_MIRROR_SOURCE|BLOCK_OP_TYPE_COMMIT_SOURCE; likewise for
>> notifiers below.
>
> We shouldn't be adding new instances of BLOCK_OP_* at all. I couldn't
> find the time yet to remove the existing ones, but any new protections
> should be using the permission system.
I agree. But does this include not fixing bugs wherever clients are
using the old op blockers?
Paolo
> I propose a new BLK_PERM_BYPASS that allows its users to bypass the
> block layer I/O functions. In other words, bdrv_aio_ioctl() would
> require that you got this permission. A dirty bitmap would keep a
> BdrvChild with perm=0, shared=BLK_PERM_ALL & ~BLK_PERM_BYPASS, so you
> can never have a dirty bitmap and a device using ioctls attached to the
> BDS at the same time.
- [Qemu-devel] [PATCH 0/2] scsi: add block job opblockers for scsi-block, Paolo Bonzini, 2018/02/07
- [Qemu-devel] [PATCH 2/2] scsi: add block job opblockers for scsi-block, Paolo Bonzini, 2018/02/07
- Re: [Qemu-devel] [PATCH 2/2] scsi: add block job opblockers for scsi-block, Fam Zheng, 2018/02/07
- Re: [Qemu-devel] [PATCH 2/2] scsi: add block job opblockers for scsi-block, Paolo Bonzini, 2018/02/08
- Re: [Qemu-devel] [PATCH 2/2] scsi: add block job opblockers for scsi-block, Kevin Wolf, 2018/02/12
- Re: [Qemu-devel] [PATCH 2/2] scsi: add block job opblockers for scsi-block,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH 2/2] scsi: add block job opblockers for scsi-block, Kevin Wolf, 2018/02/12
- Re: [Qemu-devel] [PATCH 2/2] scsi: add block job opblockers for scsi-block, Paolo Bonzini, 2018/02/12
- Re: [Qemu-devel] [PATCH 2/2] scsi: add block job opblockers for scsi-block, Kevin Wolf, 2018/02/12
- Re: [Qemu-devel] [PATCH 2/2] scsi: add block job opblockers for scsi-block, Paolo Bonzini, 2018/02/12
[Qemu-devel] [PATCH 1/2] scsi: add unrealize method for SCSI devices, Paolo Bonzini, 2018/02/07