xref: /linux/include/linux/ksm.h (revision d7597f59d1d33e9efbffa7060deb9ee5bd119e62)

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_KSM_H
#define __LINUX_KSM_H
/*
 * Memory merging support.
 *
 * This code enables dynamic sharing of identical pages found in different
 * memory areas, even if they are not shared by fork().
 */

#include <linux/bitops.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/rmap.h>
#include <linux/sched.h>
#include <linux/sched/coredump.h>

#ifdef CONFIG_KSM
int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
		unsigned long end, int advice, unsigned long *vm_flags);

void ksm_add_vma(struct vm_area_struct *vma);
int ksm_enable_merge_any(struct mm_struct *mm);

int __ksm_enter(struct mm_struct *mm);
void __ksm_exit(struct mm_struct *mm);

static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
{
	int ret;

	if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags)) {
		ret = __ksm_enter(mm);
		if (ret)
			return ret;
	}

	if (test_bit(MMF_VM_MERGE_ANY, &oldmm->flags))
		set_bit(MMF_VM_MERGE_ANY, &mm->flags);

	return 0;
}

static inline void ksm_exit(struct mm_struct *mm)
{
	if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
		__ksm_exit(mm);
}

/*
 * When do_swap_page() first faults in from swap what used to be a KSM page,
 * no problem, it will be assigned to this vma's anon_vma; but thereafter,
 * it might be faulted into a different anon_vma (or perhaps to a different
 * offset in the same anon_vma).  do_swap_page() cannot do all the locking
 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
 * a copy, and leave remerging the pages to a later pass of ksmd.
 *
 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
 * but what if the vma was unmerged while the page was swapped out?
 */
struct page *ksm_might_need_to_copy(struct page *page,
			struct vm_area_struct *vma, unsigned long address);

void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc);
void folio_migrate_ksm(struct folio *newfolio, struct folio *folio);

#ifdef CONFIG_MEMORY_FAILURE
void collect_procs_ksm(struct page *page, struct list_head *to_kill,
		       int force_early);
#endif
#else  /* !CONFIG_KSM */

static inline void ksm_add_vma(struct vm_area_struct *vma)
{
}

static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
{
	return 0;
}

static inline void ksm_exit(struct mm_struct *mm)
{
}

#ifdef CONFIG_MEMORY_FAILURE
static inline void collect_procs_ksm(struct page *page,
				     struct list_head *to_kill, int force_early)
{
}
#endif

#ifdef CONFIG_MMU
static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
		unsigned long end, int advice, unsigned long *vm_flags)
{
	return 0;
}

static inline struct page *ksm_might_need_to_copy(struct page *page,
			struct vm_area_struct *vma, unsigned long address)
{
	return page;
}

static inline void rmap_walk_ksm(struct folio *folio,
			struct rmap_walk_control *rwc)
{
}

static inline void folio_migrate_ksm(struct folio *newfolio, struct folio *old)
{
}
#endif /* CONFIG_MMU */
#endif /* !CONFIG_KSM */

#endif /* __LINUX_KSM_H */