David Dillow wrote: > On Fri, 2011-01-07 at 20:05 -0800, Roland Dreier wrote: >> > I'm sure this was tested and shown to fix the problem; I'm just confused >> > as to what the problem really was and if this is still relevant. Can >> > someone please enlighten me? >> >> At this point I'm afraid it's all lost in the mists of time, > > Yep, that's my fear. And since it is a corruption bug, I've got to tread > lightly in this area. :/ >
I don't recall to discuss or review this patch with Michael Tsirkin when he summited the patch. >> looking at the patch, I would guess that the corruption occurred when >> the target got an IO request that started at a non-page-aligned address >> but that spanned more than one page. > > That's my thought as well, but then I'm not sure this really solved > their problem. It may be more likely to occur in the FMR case, but the > initiator enables clustering, so blk_rq_map_sg() could generate the same > kinds of requests for both direct and indirect descriptors, even without > FMR. This looks to have been true since the initiator was added to the > kernel, though it is possible I'm misreading the code. > >> I don't know if the target was ever fixed, or whether that target code >> has any relevance today. > > Here's hoping someone from Mellanox can shed some light. I think that the patch is specific for srp initiator using Mellanox FMR. It tried to avoid indirect desc with Mellanox FMR having first-byte-offset != 0. Since the low level implementation of mlx4/mthca_map_phys_fmr() did not create + setup MPT for FMR with first_byte_offset != 0. The corruption can happen with any target. -vu -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html