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Re: [Qemu-devel] [RFC PATCH v2 5/6] qcow2: implement bdrv_preallocate
From: |
Peter Lieven |
Subject: |
Re: [Qemu-devel] [RFC PATCH v2 5/6] qcow2: implement bdrv_preallocate |
Date: |
Wed, 27 Nov 2013 11:03:43 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120827 Thunderbird/15.0 |
Am 27.11.2013 07:40, schrieb Fam Zheng:
> On 2013年11月27日 14:01, Hu Tao wrote:
>> On Wed, Nov 27, 2013 at 11:01:23AM +0800, Fam Zheng wrote:
>>> On 2013年11月27日 10:15, Hu Tao wrote:
>>>> Signed-off-by: Hu Tao <address@hidden>
>>>> ---
>>>> block/qcow2.c | 7 +++++++
>>>> 1 file changed, 7 insertions(+)
>>>>
>>>> diff --git a/block/qcow2.c b/block/qcow2.c
>>>> index b054a01..a23fade 100644
>>>> --- a/block/qcow2.c
>>>> +++ b/block/qcow2.c
>>>> @@ -2180,6 +2180,12 @@ static int qcow2_amend_options(BlockDriverState *bs,
>>>> return 0;
>>>> }
>>>>
>>>> +static int qcow2_preallocate(BlockDriverState *bs, int64_t offset,
>>>> + int64_t length)
>>>> +{
>>>> + return bdrv_preallocate(bs->file, offset, length);
>>>> +}
>>>> +
>>>
>>> What's the semantics of .bdrv_preallocate? I think you should map
>>> [offset, offset + length) to clusters in image file, and then
>>> forward to bs->file, rather than this direct wrapper.
>>>
>>> E.g. bdrv_preallocate(qcow2_bs, 0, cluster_size) should call
>>> bdrv_preallocate(qcow2_bs->file, offset_off_first_cluster,
>>> cluster_size).
>>
>> You mean data clusters here, right? Is there a single function to get
>> the offset of the first data cluster?
>>
>
> There is a function, qcow2_get_cluster_offset.
This should return no valid offset as long as the cluster is not allocated.
I think you actually have to "write" all clusters of a qcow2 one by one.
Eventually this write could be an fallocate call instead of a zero write.
Peter
- [Qemu-devel] [RFC PATCH v2 0/6] qemu-img: add preallocation=full, Hu Tao, 2013/11/26
- [Qemu-devel] [RFC PATCH v2 1/6] block: introduce prealloc_mode, Hu Tao, 2013/11/26
- [Qemu-devel] [RFC PATCH v2 2/6] block: add BlockDriver.bdrv_preallocate., Hu Tao, 2013/11/26
- [Qemu-devel] [RFC PATCH v2 3/6] block/raw-posix: implement bdrv_preallocate, Hu Tao, 2013/11/26
- [Qemu-devel] [RFC PATCH v2 5/6] qcow2: implement bdrv_preallocate, Hu Tao, 2013/11/26
- Re: [Qemu-devel] [RFC PATCH v2 5/6] qcow2: implement bdrv_preallocate, Fam Zheng, 2013/11/26
- Re: [Qemu-devel] [RFC PATCH v2 5/6] qcow2: implement bdrv_preallocate, Hu Tao, 2013/11/27
- Re: [Qemu-devel] [RFC PATCH v2 5/6] qcow2: implement bdrv_preallocate, Fam Zheng, 2013/11/27
- Re: [Qemu-devel] [RFC PATCH v2 5/6] qcow2: implement bdrv_preallocate,
Peter Lieven <=
- Re: [Qemu-devel] [RFC PATCH v2 5/6] qcow2: implement bdrv_preallocate, Fam Zheng, 2013/11/27
- Re: [Qemu-devel] [RFC PATCH v2 5/6] qcow2: implement bdrv_preallocate, Peter Lieven, 2013/11/27
- Re: [Qemu-devel] [RFC PATCH v2 5/6] qcow2: implement bdrv_preallocate, Hu Tao, 2013/11/28
- Re: [Qemu-devel] [RFC PATCH v2 5/6] qcow2: implement bdrv_preallocate, Peter Lieven, 2013/11/28
[Qemu-devel] [RFC PATCH v2 4/6] raw-posix: Add full image preallocation option, Hu Tao, 2013/11/26
[Qemu-devel] [RFC PATCH v2 6/6] qcow2: Add full image preallocation option, Hu Tao, 2013/11/26
Re: [Qemu-devel] [RFC PATCH v2 0/6] qemu-img: add preallocation=full, Fam Zheng, 2013/11/26