Boaz Harrosh wrote: > Mike Christie wrote: >> Boaz Harrosh wrote: >>> Playing with some tests which I admit are not 100% orthodox I have >>> stumbled upon a bug that raises a serious question: >>> >>> In the call to scsi_execute_async() in the use_sg case, must the >>> scatterlist* (pointed to by buffer) map a buffer that's contiguous in >>> virtual memory or is it allowed to map disjoint segments of memory? >> >> I thought they were continguous. I think James has said before that they >> can be disjoint. When we converted sg it did not look like sg or st >> supported disjoint. The main non dio path used a buffer from >> get_free_pages so I thought that would always be contiguous. The dio >> path then always set the first sg offset, but the rest it set to zero. >> >> How did you hit this problem? Is it with sg or st, or with some other >> code? Is it the mmap path maybe? > > OK I admit, guilty as charged, I was using it from a kernel driver, > OSD-Initiator from IBM. The code is unorthodox in mapping user space > iovects into scatterlist*. I will have to work around it than. Well, you do not have to work around it :) I want to kill scsi_execute_async and just allow the ULDs to allocate a request, call blk_rq_map_* (and add any new map helpers we need), then call blk_execute_rq_nowait. This gives the ULDs some flexibility and kills my ugly function. This is what I originally did here http://marc.theaimsgroup.com/?l=linux-scsi&m=112356952007369&w=2 For some reason, I flip flopped and went with scsi_execute_async and the scatterlist argument hack. I think I did this because I thought it would be less problems in converting the ULDs in stages. First stage was to remove scsi_request usage and clean/fix up scsi-ml and LLDs, next would be to convert to block layer functions directly, but looking back it might have been better to just go through one big headache. I think Christoph Hellwig has patches to remove scsi_execute_async as part of his bidi work. He needs help testing and reviewing them, so you should help him out instead of working around it :) - 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
