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List:       ceph-devel
Subject:    Re: [PATCH 17/18] target: add rbd backend
From:       Mike Christie <mchristi () redhat ! com>
Date:       2015-07-29 17:07:16
Message-ID: 55B90844.4050007 () redhat ! com
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On 07/29/2015 09:27 AM, Bart Van Assche wrote:
> On 07/29/15 02:23, mchristi@redhat.com wrote:
>> +static sector_t tcm_rbd_get_blocks(struct se_device *dev)
>> +{
>> +    struct tcm_rbd_dev *tcm_rbd_dev = TCM_RBD_DEV(dev);
>> +    sector_t blocks_long = tcm_rbd_dev->rbd_dev->mapping.size >>
>> +                                SECTOR_SHIFT;
>> +
>> +    if (SECTOR_SIZE == dev->dev_attrib.block_size)
>> +        return blocks_long;
>> +
>> +    switch (SECTOR_SIZE) {
>> +    case 4096:
>> +        switch (dev->dev_attrib.block_size) {
>> +        case 2048:
>> +            blocks_long <<= 1;
>> +            break;
>> +        case 1024:
>> +            blocks_long <<= 2;
>> +            break;
>> +        case 512:
>> +            blocks_long <<= 3;
>> +        default:
>> +            break;
>> +        }
>> +        break;
>> +    case 2048:
>> +        switch (dev->dev_attrib.block_size) {
>> +        case 4096:
>> +            blocks_long >>= 1;
>> +            break;
>> +        case 1024:
>> +            blocks_long <<= 1;
>> +            break;
>> +        case 512:
>> +            blocks_long <<= 2;
>> +            break;
>> +        default:
>> +            break;
>> +        }
>> +        break;
>> +    case 1024:
>> +        switch (dev->dev_attrib.block_size) {
>> +        case 4096:
>> +            blocks_long >>= 2;
>> +            break;
>> +        case 2048:
>> +            blocks_long >>= 1;
>> +            break;
>> +        case 512:
>> +            blocks_long <<= 1;
>> +            break;
>> +        default:
>> +            break;
>> +        }
>> +        break;
>> +    case 512:
>> +        switch (dev->dev_attrib.block_size) {
>> +        case 4096:
>> +            blocks_long >>= 3;
>> +            break;
>> +        case 2048:
>> +            blocks_long >>= 2;
>> +            break;
>> +        case 1024:
>> +            blocks_long >>= 1;
>> +            break;
>> +        default:
>> +            break;
>> +        }
>> +        break;
>> +    default:
>> +        break;
>> +    }
>> +
>> +    return blocks_long;
>> +}
> 
> Hello Mike,
> 
> Had you already considered to replace the above switch / case statement
> by something like the following ?
> 
> static sector_t tcm_rbd_get_blocks(struct se_device *dev)
> {
>     return TCM_RBD_DEV(dev)->rbd_dev->mapping.size >>
>                 ilog2(dev->dev_attrib.block_size);
> }
> 

Thanks. That code was copy and pasted and slightly modified from iblock.
I will code up your suggestion in the next posting.
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