On Wed, Jun 22, 2022 at 05:15:22AM +0100, Al Viro wrote: > pipe_buffer instances of a pipe are organized as a ring buffer, > with power-of-2 size. Indices are kept *not* reduced modulo ring > size, so the buffer refered to by index N is > pipe->bufs[N & (pipe->ring_size - 1)]. > > Ring size can change over the lifetime of a pipe, but not while > the pipe is locked. So for any iov_iter primitives it's a constant. > Original conversion of pipes to this layout went overboard trying > to microoptimize that - calculating pipe->ring_size - 1, storing > it in a local variable and using through the function. In some > cases it might be warranted, but most of the times it only > obfuscates what's going on in there. > > Introduce a helper (pipe_buf(pipe, N)) that would encapsulate > that and use it in the obvious cases. More will follow... > > Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > --- Looks good to me, Reviewed-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx>
