[PATCH 03/33] pgtable: Create struct ptdesc
From: Vishal Moola (Oracle) <hidden>
Date: 2023-04-17 20:52:54
Also in:
kvm, linux-arch, linux-arm-kernel, linux-m68k, linux-mips, linux-riscv, linux-s390, linux-sh, linux-um, linuxppc-dev, loongarch, sparclinux, xen-devel
Subsystem:
memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
Currently, page table information is stored within struct page. As part of simplifying struct page, create struct ptdesc for page table information. Signed-off-by: Vishal Moola (Oracle) <redacted> --- include/linux/pgtable.h | 50 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+)
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 023918666dd4..7cc6ea057ee9 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h@@ -47,6 +47,56 @@ #define pmd_pgtable(pmd) pmd_page(pmd) #endif +/** + * struct ptdesc - Memory descriptor for page tables. + * @__page_flags: Same as page flags. Unused for page tables. + * @pt_list: List of used page tables. Used for s390 and x86. + * @_pt_pad_1: Padding that aliases with page's compound head. + * @pmd_huge_pte: Protected by ptdesc->ptl, used for THPs. + * @_pt_s390_gaddr: Aliases with page's mapping. Used for s390 gmap only. + * @pt_mm: Used for x86 pgds. + * @pt_frag_refcount: For fragmented page table tracking. Powerpc and s390 only. + * @ptl: Lock for the page table. + * + * This struct overlays struct page for now. Do not modify without a good + * understanding of the issues. + */ +struct ptdesc { + unsigned long __page_flags; + + union { + struct list_head pt_list; + struct { + unsigned long _pt_pad_1; + pgtable_t pmd_huge_pte; + }; + }; + unsigned long _pt_s390_gaddr; + + union { + struct mm_struct *pt_mm; + atomic_t pt_frag_refcount; + }; + +#if ALLOC_SPLIT_PTLOCKS + spinlock_t *ptl; +#else + spinlock_t ptl; +#endif +}; + +#define TABLE_MATCH(pg, pt) \ + static_assert(offsetof(struct page, pg) == offsetof(struct ptdesc, pt)) +TABLE_MATCH(flags, __page_flags); +TABLE_MATCH(compound_head, pt_list); +TABLE_MATCH(compound_head, _pt_pad_1); +TABLE_MATCH(mapping, _pt_s390_gaddr); +TABLE_MATCH(pmd_huge_pte, pmd_huge_pte); +TABLE_MATCH(pt_mm, pt_mm); +TABLE_MATCH(ptl, ptl); +#undef TABLE_MATCH +static_assert(sizeof(struct ptdesc) <= sizeof(struct page)); + /* * A page table page can be thought of an array like this: pXd_t[PTRS_PER_PxD] *
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2.39.2