Hello, In kernel 2.6.26, the implementation of __blk_rq_map_user changed and now includes a call to bio_copy_user: uaddr = (unsigned long) ubuf; alignment = queue_dma_alignment(q) | q->dma_pad_mask; if (!(uaddr & alignment) && !(len & alignment)) bio = bio_map_user(q, NULL, uaddr, len, reading); else bio = bio_copy_user(q, uaddr, len, reading); bio_copy_user uses the HBA's scatter-gather pages for the copy. The problem I face is that if the data size is not aligned properly, or the len parameter does not divide properly, and the transfer is greater than the number of scatter-gather pages, the IO operation will fail. I am considering increasing the size of my data buffer to meet the length-alignment requirement and changing the 'len' parameter passed into blk_rq_map_user to include a larger size than my CDB transfer length. The tape device should still honor the CDB write length, so unless there are other limitations imposed by the Linux kernel or SCSI subsystem, I think this is a workable solution. Does anyone in this list know if there is are requirements against sending a larger buffer length than CDB transfer length? Thanks in advance. Brett Dennis IBM tape device driver developer -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
