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29cb805196
Not all huge_pte helper APIs explicitly provide the size of the huge_pte. So the helpers have to depend on various methods to determine the size of the huge_pte. Some of these methods are dubious. Let's clean up the code to use preferred methods and retire the dubious ones. The options in order of preference: - If size is provided as parameter, use it together with num_contig_ptes(). This is explicit and works for both present and non-present ptes. - If vma is provided as a parameter, retrieve size via huge_page_size(hstate_vma(vma)) and use it together with num_contig_ptes(). This is explicit and works for both present and non-present ptes. - If the pte is present and contiguous, use find_num_contig() to walk the pgtable to find the level and infer the number of ptes from level. Only works for *present* ptes. - If the pte is present and not contiguous and you can infer from this that only 1 pte needs to be operated on. This is ok if you don't care about the absolute size, and just want to know the number of ptes. - NEVER rely on resolving the PFN of a present pte to a folio and getting the folio's size. This is fragile at best, because there is nothing to stop the core-mm from allocating a folio twice as big as the huge_pte then mapping it across 2 consecutive huge_ptes. Or just partially mapping it. Where we require that the pte is present, add warnings if not-present. Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> Tested-by: Luiz Capitulino <luizcap@redhat.com> Link: https://lore.kernel.org/r/20250422081822.1836315-2-ryan.roberts@arm.com Signed-off-by: Will Deacon <will@kernel.org>
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.