On Thu, Jan 25, 2018 at 11:34:23AM -0500, Doug Ledford wrote: > > - Should I be wrong about no callers already holding mmap_sem, > > I still think calling gup without the mutex makes sense for > > improved paralellism. Now, if callers can hold the mmap_sem, > > it's wrong to do copy_from_user right before calling mthca_map_user_db. > > So, if I understand you correctly, we (well, you and Al would be more > correct, we haven't looked into the situation yet, so Mellanox people > that worked on this in the day might now, or someone taking the time to > research it could find out) don't have a clear understanding of all the > conditions this function is called under, and so we actually don't know > what the best way forward is to fix it? I looked at it enough to be confident that mthca_map_user_db is never called with mmap_sem held. Also pretty confident that mthca_unmap_user_db is never called with mmap_sem. So how about just grabbing mmap_sem around the call to get_user_pages and no other changes? Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
