linux/include/linux/pagewalk.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_PAGEWALK_H
#define _LINUX_PAGEWALK_H

#include <linux/mm.h>

struct mm_walk;

/* Locking requirement during a page walk. */
enum page_walk_lock { … };

/**
 * struct mm_walk_ops - callbacks for walk_page_range
 * @pgd_entry:		if set, called for each non-empty PGD (top-level) entry
 * @p4d_entry:		if set, called for each non-empty P4D entry
 * @pud_entry:		if set, called for each non-empty PUD entry
 * @pmd_entry:		if set, called for each non-empty PMD entry
 *			this handler is required to be able to handle
 *			pmd_trans_huge() pmds.  They may simply choose to
 *			split_huge_page() instead of handling it explicitly.
 * @pte_entry:		if set, called for each PTE (lowest-level) entry,
 *			including empty ones
 * @pte_hole:		if set, called for each hole at all levels,
 *			depth is -1 if not known, 0:PGD, 1:P4D, 2:PUD, 3:PMD.
 *			Any folded depths (where PTRS_PER_P?D is equal to 1)
 *			are skipped.
 * @hugetlb_entry:	if set, called for each hugetlb entry. This hook
 *			function is called with the vma lock held, in order to
 *			protect against a concurrent freeing of the pte_t* or
 *			the ptl. In some cases, the hook function needs to drop
 *			and retake the vma lock in order to avoid deadlocks
 *			while calling other functions. In such cases the hook
 *			function must either refrain from accessing the pte or
 *			ptl after dropping the vma lock, or else revalidate
 *			those items after re-acquiring the vma lock and before
 *			accessing them.
 * @test_walk:		caller specific callback function to determine whether
 *			we walk over the current vma or not. Returning 0 means
 *			"do page table walk over the current vma", returning
 *			a negative value means "abort current page table walk
 *			right now" and returning 1 means "skip the current vma"
 *			Note that this callback is not called when the caller
 *			passes in a single VMA as for walk_page_vma().
 * @pre_vma:            if set, called before starting walk on a non-null vma.
 * @post_vma:           if set, called after a walk on a non-null vma, provided
 *                      that @pre_vma and the vma walk succeeded.
 *
 * p?d_entry callbacks are called even if those levels are folded on a
 * particular architecture/configuration.
 */
struct mm_walk_ops { … };

/*
 * Action for pud_entry / pmd_entry callbacks.
 * ACTION_SUBTREE is the default
 */
enum page_walk_action { … };

/**
 * struct mm_walk - walk_page_range data
 * @ops:	operation to call during the walk
 * @mm:		mm_struct representing the target process of page table walk
 * @pgd:	pointer to PGD; only valid with no_vma (otherwise set to NULL)
 * @vma:	vma currently walked (NULL if walking outside vmas)
 * @action:	next action to perform (see enum page_walk_action)
 * @no_vma:	walk ignoring vmas (vma will always be NULL)
 * @private:	private data for callbacks' usage
 *
 * (see the comment on walk_page_range() for more details)
 */
struct mm_walk { … };

int walk_page_range(struct mm_struct *mm, unsigned long start,
		unsigned long end, const struct mm_walk_ops *ops,
		void *private);
int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
			  unsigned long end, const struct mm_walk_ops *ops,
			  pgd_t *pgd,
			  void *private);
int walk_page_range_vma(struct vm_area_struct *vma, unsigned long start,
			unsigned long end, const struct mm_walk_ops *ops,
			void *private);
int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
		void *private);
int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
		      pgoff_t nr, const struct mm_walk_ops *ops,
		      void *private);

folio_walk_flags_t;

/*
 * Walk migration entries as well. Careful: a large folio might get split
 * concurrently.
 */
#define FW_MIGRATION …

/* Walk shared zeropages (small + huge) as well. */
#define FW_ZEROPAGE …

enum folio_walk_level { … };

/**
 * struct folio_walk - folio_walk_start() / folio_walk_end() data
 * @page:	exact folio page referenced (if applicable)
 * @level:	page table level identifying the entry type
 * @pte:	pointer to the page table entry (FW_LEVEL_PTE).
 * @pmd:	pointer to the page table entry (FW_LEVEL_PMD).
 * @pud:	pointer to the page table entry (FW_LEVEL_PUD).
 * @ptl:	pointer to the page table lock.
 *
 * (see folio_walk_start() documentation for more details)
 */
struct folio_walk { … };

struct folio *folio_walk_start(struct folio_walk *fw,
		struct vm_area_struct *vma, unsigned long addr,
		folio_walk_flags_t flags);

#define folio_walk_end(__fw, __vma) …

#endif /* _LINUX_PAGEWALK_H */