Re: [Qemu-devel] [PULL 03/10] pc-bios/s390-ccw: handle different sector sizes

[Eugene \"jno\" Dvurechenski]

On 06/27/2014 03:55 PM, Christian Borntraeger wrote:
>>> -    const int max_entries = (SECTOR_SIZE / sizeof(ScsiBlockPtr));
>>> +    const int max_entries = (MAX_SECTOR_SIZE / sizeof(ScsiBlockPtr));
>>
>> Is this really safe to increase? Doesn't max_entries depend on the real 
>> sector size?
> 
> I think this is now covered by this if statement:
>             if (bprs[i].blockct == 0 && unused_space(&bprs[i + 1],
>                 sizeof(ScsiBlockPtr))) {
> 
> which was introduced by commit c77cd87cf54f003748f29c14ea1ddaecfc5c653f 
> (pc-bios/s390-ccw: fix for fragmented SCSI bootmap).
> 
> So strictly speaking this if statement might not be needed any more:
>         if (i == (max_entries - 1)) {
> 
> Eugene, can you confirm?  If yes we could add this patch later on as a 
> cleanup:

I'd preserve both checks.
In theory, we may catch a table that consumes all scratch space and
leave no unused entry.

Plus, this check for zero counter and last entry is for "continuation"
pointer, not for end-of-table by itself.

I think now, this code may need even few more checks to cover more cases...

-- 
Best Regards,
Eugene "jno" Dvurechenski
zLinux (KVM) Development - Software Engineer
IBM Russia - Science & Technology Center
phone: +7 (495) 660 8940 ext. 1021

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