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2dcedb2a54
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... Reviewed-by: Jeff Layton <jlayton@kernel.org> Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.