From: Peter Xu <peterx@xxxxxxxxxx> There's one small section already, but since we're going to remove pXd_huge(), that comment may start to obsolete. Rewrite that section with more information, hopefully with that the API is crystal clear on what it implies. Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> --- include/linux/pgtable.h | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 85fc7554cd52..6b0d222a7fad 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -1770,11 +1770,25 @@ typedef unsigned int pgtbl_mod_mask; #endif /* - * p?d_leaf() - true if this entry is a final mapping to a physical address. - * This differs from p?d_huge() by the fact that they are always available (if - * the architecture supports large pages at the appropriate level) even - * if CONFIG_HUGETLB_PAGE is not defined. - * Only meaningful when called on a valid entry. + * pXd_leaf() is the API to check whether a pgtable entry is a huge page + * mapping. It should work globally across all archs, without any + * dependency on CONFIG_* options. For architectures that do not support + * huge mappings on specific levels, below fallbacks will be used. + * + * A leaf pgtable entry should always imply the following: + * + * - It is a "present" entry. IOW, before using this API, please check it + * with pXd_present() first. NOTE: it may not always mean the "present + * bit" is set. For example, PROT_NONE entries are always "present". + * + * - It should _never_ be a swap entry of any type. Above "present" check + * should have guarded this, but let's be crystal clear on this. + * + * - It should contain a huge PFN, which points to a huge page larger than + * PAGE_SIZE of the platform. The PFN format isn't important here. + * + * - It should cover all kinds of huge mappings (e.g., pXd_trans_huge(), + * pXd_devmap(), or hugetlb mappings). */ #ifndef pgd_leaf #define pgd_leaf(x) false -- 2.44.0
