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31b00fe1e2
Add scatterwalk_next() which consolidates scatterwalk_clamp() and scatterwalk_map(). Also add scatterwalk_done_src() and scatterwalk_done_dst() which consolidate scatterwalk_unmap(), scatterwalk_advance(), and scatterwalk_done() or scatterwalk_pagedone(). A later patch will remove scatterwalk_done() and scatterwalk_pagedone(). The new code eliminates the error-prone 'more' parameter. Advancing to the next sg entry now only happens just-in-time in scatterwalk_next(). The new code also pairs the dcache flush more closely with the actual write, similar to memcpy_to_page(). Previously it was paired with advancing to the next page. This is currently causing bugs where the dcache flush is incorrectly being skipped, usually due to scatterwalk_copychunks() being called without a following scatterwalk_done(). The dcache flush may have been placed where it was in order to not call flush_dcache_page() redundantly when visiting a page more than once. However, that case is rare in practice, and most architectures either do not implement flush_dcache_page() anyway or implement it lazily where it just clears a page flag. Another limitation of the old code was that by the time the flush happened, there was no way to tell if more than one page needed to be flushed. That has been sufficient because the code goes page by page, but I would like to optimize that on !HIGHMEM platforms. The new code makes this possible, and a later patch will implement this optimization. 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.