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Quelle mapping_dirty_helpers.c Sprache: C |
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// SPDX-License-Identifier: GPL-2.0
#include <linux/pagewalk.h> #include <linux/hugetlb.h> #include <linux/bitops.h> #include <linux/mmu_notifier.h> #include <linux/mm_inline.h> #include <asm/cacheflush.h> #include <asm/tlbflush.h> /** * struct wp_walk - Private struct for pagetable walk callbacks * @range: Range for mmu notifiers * @tlbflush_start: Address of first modified pte * @tlbflush_end: Address of last modified pte + 1 * @total: Total number of modified ptes */ struct wp_walk { struct mmu_notifier_range range; unsigned long tlbflush_start; unsigned long tlbflush_end; unsigned long total; }; /** * wp_pte - Write-protect a pte * @pte: Pointer to the pte * @addr: The start of protecting virtual address * @end: The end of protecting virtual address * @walk: pagetable walk callback argument * * The function write-protects a pte and records the range in * virtual address space of touched ptes for efficient range TLB flushes. */ static int wp_pte(pte_t *pte, unsigned long addr, unsigned long end, struct mm_walk *walk) { struct wp_walk *wpwalk = walk->private; pte_t ptent = ptep_get(pte); if (pte_write(ptent)) { pte_t old_pte = ptep_modify_prot_start(walk->vma, addr, pte); ptent = pte_wrprotect(old_pte); ptep_modify_prot_commit(walk->vma, addr, pte, old_pte, ptent); wpwalk->total++; wpwalk->tlbflush_start = min(wpwalk->tlbflush_start, addr); wpwalk->tlbflush_end = max(wpwalk->tlbflush_end, addr + PAGE_SIZE); } return 0; } /** * struct clean_walk - Private struct for the clean_record_pte function. * @base: struct wp_walk we derive from * @bitmap_pgoff: Address_space Page offset of the first bit in @bitmap * @bitmap: Bitmap with one bit for each page offset in the address_space range * covered. * @start: Address_space page offset of first modified pte relative * to @bitmap_pgoff * @end: Address_space page offset of last modified pte relative * to @bitmap_pgoff */ struct clean_walk { struct wp_walk base; pgoff_t bitmap_pgoff; unsigned long *bitmap; pgoff_t start; pgoff_t end; }; #define to_clean_walk(_wpwalk) container_of(_wpwalk, struct clean_walk, base) /** * clean_record_pte - Clean a pte and record its address space offset in a * bitmap * @pte: Pointer to the pte * @addr: The start of virtual address to be clean * @end: The end of virtual address to be clean * @walk: pagetable walk callback argument * * The function cleans a pte and records the range in * virtual address space of touched ptes for efficient TLB flushes. * It also records dirty ptes in a bitmap representing page offsets * in the address_space, as well as the first and last of the bits * touched. */ static int clean_record_pte(pte_t *pte, unsigned long addr, unsigned long end, struct mm_walk *walk) { struct wp_walk *wpwalk = walk->private; struct clean_walk *cwalk = to_clean_walk(wpwalk); pte_t ptent = ptep_get(pte); if (pte_dirty(ptent)) { pgoff_t pgoff = ((addr - walk->vma->vm_start) >> PAGE_SHIFT) + walk->vma->vm_pgoff - cwalk->bitmap_pgoff; pte_t old_pte = ptep_modify_prot_start(walk->vma, addr, pte); ptent = pte_mkclean(old_pte); ptep_modify_prot_commit(walk->vma, addr, pte, old_pte, ptent); wpwalk->total++; wpwalk->tlbflush_start = min(wpwalk->tlbflush_start, addr); wpwalk->tlbflush_end = max(wpwalk->tlbflush_end, addr + PAGE_SIZE); __set_bit(pgoff, cwalk->bitmap); cwalk->start = min(cwalk->start, pgoff); cwalk->end = max(cwalk->end, pgoff + 1); } return 0; } /* * wp_clean_pmd_entry - The pagewalk pmd callback. * * Dirty-tracking should take place on the PTE level, so * WARN() if encountering a dirty huge pmd. * Furthermore, never split huge pmds, since that currently * causes dirty info loss. The pagefault handler should do * that if needed. */ static int wp_clean_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long end, struct mm_walk *walk) { pmd_t pmdval = pmdp_get_lockless(pmd); /* Do not split a huge pmd, present or migrated */ if (pmd_trans_huge(pmdval)) { WARN_ON(pmd_write(pmdval) || pmd_dirty(pmdval)); walk->action = ACTION_CONTINUE; } return 0; } /* * wp_clean_pud_entry - The pagewalk pud callback. * * Dirty-tracking should take place on the PTE level, so * WARN() if encountering a dirty huge puds. * Furthermore, never split huge puds, since that currently * causes dirty info loss. The pagefault handler should do * that if needed. */ static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end, struct mm_walk *walk) { #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD pud_t pudval = READ_ONCE(*pud); /* Do not split a huge pud */ if (pud_trans_huge(pudval)) { WARN_ON(pud_write(pudval) || pud_dirty(pudval)); walk->action = ACTION_CONTINUE; } #endif return 0; } /* * wp_clean_pre_vma - The pagewalk pre_vma callback. * * The pre_vma callback performs the cache flush, stages the tlb flush * and calls the necessary mmu notifiers. */ static int wp_clean_pre_vma(unsigned long start, unsigned long end, struct mm_walk *walk) { struct wp_walk *wpwalk = walk->private; wpwalk->tlbflush_start = end; wpwalk->tlbflush_end = start; mmu_notifier_range_init(&wpwalk->range, MMU_NOTIFY_PROTECTION_PAGE, 0, walk->mm, start, end); mmu_notifier_invalidate_range_start(&wpwalk->range); flush_cache_range(walk->vma, start, end); /* * We're not using tlb_gather_mmu() since typically * only a small subrange of PTEs are affected, whereas * tlb_gather_mmu() records the full range. */ inc_tlb_flush_pending(walk->mm); return 0; } /* * wp_clean_post_vma - The pagewalk post_vma callback. * * The post_vma callback performs the tlb flush and calls necessary mmu * notifiers. */ static void wp_clean_post_vma(struct mm_walk *walk) { struct wp_walk *wpwalk = walk->private; if (mm_tlb_flush_nested(walk->mm)) flush_tlb_range(walk->vma, wpwalk->range.start, wpwalk->range.end); else if (wpwalk->tlbflush_end > wpwalk->tlbflush_start) flush_tlb_range(walk->vma, wpwalk->tlbflush_start, wpwalk->tlbflush_end); mmu_notifier_invalidate_range_end(&wpwalk->range); dec_tlb_flush_pending(walk->mm); } /* * wp_clean_test_walk - The pagewalk test_walk callback. * * Won't perform dirty-tracking on COW, read-only or HUGETLB vmas. */ static int wp_clean_test_walk(unsigned long start, unsigned long end, struct mm_walk *walk) { vm_flags_t vm_flags = READ_ONCE(walk->vma->vm_flags); /* Skip non-applicable VMAs */ if ((vm_flags & (VM_SHARED | VM_MAYWRITE | VM_HUGETLB)) != (VM_SHARED | VM_MAYWRITE)) return 1; return 0; } static const struct mm_walk_ops clean_walk_ops = { .pte_entry = clean_record_pte, .pmd_entry = wp_clean_pmd_entry, .pud_entry = wp_clean_pud_entry, .test_walk = wp_clean_test_walk, .pre_vma = wp_clean_pre_vma, .post_vma = wp_clean_post_vma }; static const struct mm_walk_ops wp_walk_ops = { .pte_entry = wp_pte, .pmd_entry = wp_clean_pmd_entry, .pud_entry = wp_clean_pud_entry, .test_walk = wp_clean_test_walk, .pre_vma = wp_clean_pre_vma, .post_vma = wp_clean_post_vma }; /** * wp_shared_mapping_range - Write-protect all ptes in an address space range * @mapping: The address_space we want to write protect * @first_index: The first page offset in the range * @nr: Number of incremental page offsets to cover * * Note: This function currently skips transhuge page-table entries, since * it's intended for dirty-tracking on the PTE level. It will warn on * encountering transhuge write-enabled entries, though, and can easily be * extended to handle them as well. * * Return: The number of ptes actually write-protected. Note that * already write-protected ptes are not counted. */ unsigned long wp_shared_mapping_range(struct address_space *mapping, pgoff_t first_index, pgoff_t nr) { struct wp_walk wpwalk = { .total = 0 }; i_mmap_lock_read(mapping); WARN_ON(walk_page_mapping(mapping, first_index, nr, &wp_walk_ops, &wpwalk)); i_mmap_unlock_read(mapping); return wpwalk.total; } EXPORT_SYMBOL_GPL(wp_shared_mapping_range); /** * clean_record_shared_mapping_range - Clean and record all ptes in an * address space range * @mapping: The address_space we want to clean * @first_index: The first page offset in the range * @nr: Number of incremental page offsets to cover * @bitmap_pgoff: The page offset of the first bit in @bitmap * @bitmap: Pointer to a bitmap of at least @nr bits. The bitmap needs to * cover the whole range @first_index..@first_index + @nr. * @start: Pointer to number of the first set bit in @bitmap. * is modified as new bits are set by the function. * @end: Pointer to the number of the last set bit in @bitmap. * none set. The value is modified as new bits are set by the function. * * When this function returns there is no guarantee that a CPU has * not already dirtied new ptes. However it will not clean any ptes not * reported in the bitmap. The guarantees are as follows: * * * All ptes dirty when the function starts executing will end up recorded * in the bitmap. * * All ptes dirtied after that will either remain dirty, be recorded in the * bitmap or both. * * If a caller needs to make sure all dirty ptes are picked up and none * additional are added, it first needs to write-protect the address-space * range and make sure new writers are blocked in page_mkwrite() or * pfn_mkwrite(). And then after a TLB flush following the write-protection * pick up all dirty bits. * * This function currently skips transhuge page-table entries, since * it's intended for dirty-tracking on the PTE level. It will warn on * encountering transhuge dirty entries, though, and can easily be extended * to handle them as well. * * Return: The number of dirty ptes actually cleaned. */ unsigned long clean_record_shared_mapping_range(struct address_space *mapping, pgoff_t first_index, pgoff_t nr, pgoff_t bitmap_pgoff, unsigned long *bitmap, pgoff_t *start, pgoff_t *end) { bool none_set = (*start >= *end); struct clean_walk cwalk = { .base = { .total = 0 }, .bitmap_pgoff = bitmap_pgoff, .bitmap = bitmap, .start = none_set ? nr : *start, .end = none_set ? 0 : *end, }; i_mmap_lock_read(mapping); WARN_ON(walk_page_mapping(mapping, first_index, nr, &clean_walk_ops, &cwalk.base)); i_mmap_unlock_read(mapping); *start = cwalk.start; *end = cwalk.end; return cwalk.base.total; } EXPORT_SYMBOL_GPL(clean_record_shared_mapping_range); ¤ Dauer der Verarbeitung: 0.6 Sekunden ¤*© Formatika GbR, Deutschland |
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2026-03-28