Re: nr_pages calculation in scsi_req_map_sg()

["Jan Beulich" <jbeulich@novell.com>]

>>> Boaz Harrosh <bharrosh@panasas.com> 22.07.08 15:28 >>>
>Jan Beulich wrote:
>> James,
>> 
>> while reviewing code derived from that function I found this calculation
>> to be suspicious: I would think that it should get it wrong when both
>> start and end of the buffer area are misaligned (e.g. consider the case
>> where sgl->offset equals PAGE_SIZE-1 and bufflen equals 2 - the result
>> would be 1 when it should have been 2).
>> Is there something preventing this from happening?
>> 
>> Thanks, Jan
>> 
>> --
>
>It has been discussed before for example look here:
>http://www.spinics.net/lists/linux-scsi/msg13454.html 
>
>But for me the main reason it is not fixed is because
>this is only called from scsi_execute_async() which
>is a deprecated function. It is still used by old code
>which is supposed to be removed soon. Any new code will
>not be accepted if it uses scsi_execute_async().

No, that's a different issue: Even if the sg elements are all contiguous,
the count can be wrong, as described in the original mail. And as said,
I found this in code cloned from scsi_req_map_sg(), hence would be
interested in confirmation of that fact (or explanation why it's not an
issue) regardless of the function itself sitting in a to-be-removed code
path only.

Thanks, Jan