On Sat, Apr 18, 2015 at 08:45:19AM +0200, Matias Bjorling wrote: > The low level drivers will be NVMe and vendor's own PCI-e drivers. It's very > generic in their nature. Each driver would duplicate the same work. Both > could have normal and open-channel drives attached. I didn't say the work should move into the driver, bur rather that driver should talk to the open channel ssd code directly instead of hooking into the core block code. > I'll like to keep blk-mq in the loop. I don't think it will be pretty to > have two data paths in the drivers. For blk-mq, bios are splitted/merged on > the way down. Thus, the actual physical addresses needs aren't known before > the IO is diced to the right size. But you _do_ have two different data path already. Nothing says you can't use blk-mq for your data path, ut it should be a separate entry point. Similar to say how a SCSI disk and MMC device both use the block layer but still use different entry points. > The reason it shouldn't be under the a single block device, is that a target > should be able to provide a global address space. > That allows the address > space to grow/shrink dynamically with the disks. Allowing a continuously > growing address space, where disks can be added/removed as requirements grow > or flash ages. Not on a sector level, but on a flash block level. I don't understand what you mean with a single block device here, but I suspect we're talking past each other somehow. > >>In the future, applications can have an API to get/put flash block directly. > >>(using the blk_nvm_[get/put]_blk interface). > > > >s/application/filesystem/? > > > > Applications. The goal is that key value stores, e.g. RocksDB, Aerospike, > Ceph and similar have direct access to flash storage. There won't be a > kernel file-system between. > > The get/put interface can be seen as a space reservation interface for where > a given process is allowed to access the storage media. > > It can also be seen in the way that we provide a block allocator in the > kernel, while applications implement the rest of "file-system" in > user-space, specially optimized for their data structures. This makes a lot > of sense for a small subset (LSM, Fractal trees, etc.) of database > applications. While we'll need a proper API for that first it's just another reason of why we shouldnt shoe horn the open channel ssd support into the block layer. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
