On Tue, 2024-04-02 at 22:22 +0530, Kanchan Joshi wrote: > On 4/2/2024 4:15 PM, Dongyang Li wrote: > > Martin, Kanchan, > > > > > > Kanchan, > > > > > > > - Generic user interface that user-space can use to exchange > > > > meta. > > > > A > > > > new io_uring opcode IORING_OP_READ/WRITE_META - seems feasible > > > > for > > > > direct IO. > > > > > > Yep. I'm interested in this too. Reviving this effort is near the > > > top > > > of > > > my todo list so I'm happy to collaborate. > > If we are going to have a interface to exchange meta/integrity to > > user- > > space, we could also have a interface in kernel to do the same? > > Not sure if I follow. > Currently when blk-integrity allocates/attaches the meta buffer, it > decides what to put in it and how to go about integrity > generation/verification. > When user-space is sending the meta buffer, it will decide what to > put/verify. Passed meta buffer will be used directly, and blk- > integrity > will only facilitate that without doing any in-kernel > generation/verification. This is what I was trying to get, but for in-kernel users instead of user-space, however... > > > It would be useful for some network filesystem/block device drivers > > like nbd/drbd/NVMe-oF to use blk-integrity as network checksum, and > > the > > same checksum covers the I/O on the server as well. > > > > The integrity can be generated on the client and send over network, > > on server blk-integrity can just offload to storage. > > Verify follows the same principle: on server blk-integrity gets > > the PI from storage using the interface, and send over network, > > on client we can do the usual verify. > > > > In the past we tried to achieve this, there's patch to add optional > > generate/verify functions and they take priority over the ones from > > the > > integrity profile, and the optional generate/verify functions does > > the > > meta/PI exchange, but that didn't get traction. It would be much > > better > > if we can have an bio interface for this. > > Any link to the patches? > I am not sure what this bio interface is for. Does this mean > verify/generate functions to be specified for each bio? Yes, and it's an awkward way to save the meta/PI before the PI buffer gets freed right after verify. > Now also in-kernel users can add the meta buffer to the bio. It is up > to > the bio owner to implement any custom processing on this meta buffer. This makes me realise if in-kernel user does its own meta/PI buffer management without bio_integrity_prep(), it won't be freed by bio_integrity_free() and we can put/get to the meta/PI buffer and reuse the PI data. I will give this a try. Thanks
