On Mon, Nov 03, 2014 at 07:05:52AM +0800, Herbert Xu wrote: > Currently the functions aio_read/aio_write use a const iov as > input. This is unnecessary as all their callers supply a > stack-based or kmalloced iov which is never reused. Conceptually > this is fine because iovs supplied to aio_read/aio_write ultimately > come from user-space so we always have to make a copy of them for > the kernel. > > This is also a joke because for as long (since 2.1.15) as we've > had the const iov, the network stack (currently through do_sock_read > and do_sock_write) has been casting the const away. IOW if anybody > did supply a const iov they would crash and burn if they ever > entered the network stack. > > The network stack needs a non-const iov because it iterates through > the iov as it reads/writes data. > > So we have two alternatives, either change the network stack to > not touch the iovs or make the iovs non-const. > > As there is no reason for the iovs to be const in the first place, > I have taken the second choice and changed all aio_read/aio_write > functions to use non-const iovs.
NAK with extreme prejudice. The right way to deal with that is to convert the socket side of things to iov_iter. And give it a consistent behaviour, while we are at it (some protocols do advance the damn thing, so do not). There are _very_ good reasons to have those iovecs unchanged - if you look at the callers on the socket side, you'll see a bunch that has to _copy_ iovec just to avoid it being buggered. And you get rather suboptimal behaviour in memcpy_fromiovec() and friends, exactly because you have to skip through the emptied elements. IOW, no way in hell. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
