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Add memcpy_from_sglist() and memcpy_to_sglist() which are more readable versions of scatterwalk_map_and_copy() with the 'out' argument 0 and 1 respectively. They follow the same argument order as memcpy_from_page() and memcpy_to_page() from <linux/highmem.h>. Note that in the case of memcpy_from_sglist(), this also happens to be the same argument order that scatterwalk_map_and_copy() uses. The new code is also faster, mainly because it builds the scatter_walk directly without creating a temporary scatterlist. E.g., a 20% performance improvement is seen for copying the AES-GCM auth tag. Make scatterwalk_map_and_copy() be a wrapper around memcpy_from_sglist() and memcpy_to_sglist(). Callers of scatterwalk_map_and_copy() should be updated to call memcpy_from_sglist() or memcpy_to_sglist() directly, but there are a lot of them so they aren't all being updated right away. Also add functions memcpy_from_scatterwalk() and memcpy_to_scatterwalk() which are similar but operate on a scatter_walk instead of a scatterlist. These will replace scatterwalk_copychunks() with the 'out' argument 0 and 1 respectively. Their behavior differs slightly from scatterwalk_copychunks() in that they automatically take care of flushing the dcache when needed, making them easier to use. scatterwalk_copychunks() itself is left unchanged for now. It will be removed after its callers are updated to use other functions instead. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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.