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Re: [Qemu-block] [PATCH v3] virtio-blk: trivial code optimization
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-block] [PATCH v3] virtio-blk: trivial code optimization |
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Date: |
Tue, 10 Nov 2015 10:51:54 +0100 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 |
On 10/11/2015 07:35, Gonglei wrote:
>> > nb_sectors - int
>> > max_xfer_len - int
>> > req->qiov.size - size_t
>> > BDRV_SECTOR_SIZE - unsigned long long
>> >
>> > Therefore this expression is an int > unsigned long long comparison.
>> >
> Sorry, I'm confused.
> max_xfer_len is int,
> "req->qiov.size / BDRV_SECTOR_SIZE" is unsigned long long,
> so, "max_xfer_len - req->qiov.size / BDRV_SECTOR_SIZE" will be int,
No, the result will be unsigned long long, and the comparison is wrong
if max_xfer_len < req->qiov.size / BDRV_SECTOR_SIZE.
Paolo
> and nb_sectors is int too, so this comparison is right. Am I wrong?
>