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35c8711c8f
Our provided buffer interface only allows selection of a single buffer. Add an API that allows getting/peeking multiple buffers at the same time. This is only implemented for the ring provided buffers. It could be added for the legacy provided buffers as well, but since it's strongly encouraged to use the new interface, let's keep it simpler and just provide it for the new API. The legacy interface will always just select a single buffer. There are two new main functions: io_buffers_select(), which selects up as many buffers as it can. The caller supplies the iovec array, and io_buffers_select() may allocate a bigger array if the 'out_len' being passed in is non-zero and bigger than what fits in the provided iovec. Buffers grabbed with this helper are permanently assigned. io_buffers_peek(), which works like io_buffers_select(), except they can be recycled, if needed. Callers using either of these functions should call io_put_kbufs() rather than io_put_kbuf() at completion time. The peek interface must be called with the ctx locked from peek to completion. This add a bit state for the request: - REQ_F_BUFFERS_COMMIT, which means that the the buffers have been peeked and should be committed to the buffer ring head when they are put as part of completion. Prior to this, req->buf_list was cleared to NULL when committed. Signed-off-by: Jens Axboe <axboe@kernel.dk>
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 reStructuredText 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.