On Wed, Nov 05, 2014 at 06:49:45PM +0000, Al Viro wrote: > Not really. A minor nitpick is that you've missed port_fops_splice_write(), > but the real bitch isn't that and not even the sockets (see the fun with > iov_iter sendmsg/recvmsg work getting resurrected). It's that NULL > ->splice_write() means default_file_splice_write. IOW, you'd need either > ->write_iter() for _everything_ (with support of bvec-backed ones included, > since that's what iter_file_splice_write() will feed to ->write_iter()), > or you need to have do_splice_from() check if ->write_iter is NULL and > go for default_file_splice_write() instead of iter_file_splice_write(). > > The latter might be doable, but the former is really over the top - for > that we'd need to touch every driver instance of ->write() out there. > You want to do that, it's your funeral... The latter is what I thought off. And yes, the socket work looks good, especially if we can get rid of ->sendpage as well. That'll require passing new flags somewhere, the ones in the iocb added for preadv2/pwritev2 might be usable. > > Similarly it seems to be like we could kill ->splice_read by > > implementing an equivalent iteration over ->read_iter. > > Hard to do. I agree that we want to, but it'll take quite a bit of work > on iov_iter primitives, I'm afraid. At the very least, we want a variant > of iov_iter that could steal pages. Don't forget that a large part of > the rationale behind splice_read was the ability to play zero-copy games. > > I'm not sure if it will happen this cycle; there's more than enough fun > on the net/* side. _If_ that ends up done faster than I expect it to be, > ->splice_read() is the obvious next target. And zero copy games would become a lot less nasty if they could go straight through ->read_iter instead of the current abuses of splice infrastructure. Same for sendfile, btw. -- 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
