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Diffstat (limited to 'include/linux/rmap.h')
| -rw-r--r-- | include/linux/rmap.h | 495 |
1 files changed, 495 insertions, 0 deletions
diff --git a/include/linux/rmap.h b/include/linux/rmap.h new file mode 100644 index 000000000..7d1ecd9b4 --- /dev/null +++ b/include/linux/rmap.h @@ -0,0 +1,495 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_RMAP_H +#define _LINUX_RMAP_H +/* + * Declarations for Reverse Mapping functions in mm/rmap.c + */ + +#include <linux/list.h> +#include <linux/slab.h> +#include <linux/mm.h> +#include <linux/rwsem.h> +#include <linux/memcontrol.h> +#include <linux/highmem.h> +#include <linux/pagemap.h> +#include <linux/memremap.h> + +/* + * The anon_vma heads a list of private "related" vmas, to scan if + * an anonymous page pointing to this anon_vma needs to be unmapped: + * the vmas on the list will be related by forking, or by splitting. + * + * Since vmas come and go as they are split and merged (particularly + * in mprotect), the mapping field of an anonymous page cannot point + * directly to a vma: instead it points to an anon_vma, on whose list + * the related vmas can be easily linked or unlinked. + * + * After unlinking the last vma on the list, we must garbage collect + * the anon_vma object itself: we're guaranteed no page can be + * pointing to this anon_vma once its vma list is empty. + */ +struct anon_vma { + struct anon_vma *root; /* Root of this anon_vma tree */ + struct rw_semaphore rwsem; /* W: modification, R: walking the list */ + /* + * The refcount is taken on an anon_vma when there is no + * guarantee that the vma of page tables will exist for + * the duration of the operation. A caller that takes + * the reference is responsible for clearing up the + * anon_vma if they are the last user on release + */ + atomic_t refcount; + + /* + * Count of child anon_vmas. Equals to the count of all anon_vmas that + * have ->parent pointing to this one, including itself. + * + * This counter is used for making decision about reusing anon_vma + * instead of forking new one. See comments in function anon_vma_clone. + */ + unsigned long num_children; + /* Count of VMAs whose ->anon_vma pointer points to this object. */ + unsigned long num_active_vmas; + + struct anon_vma *parent; /* Parent of this anon_vma */ + + /* + * NOTE: the LSB of the rb_root.rb_node is set by + * mm_take_all_locks() _after_ taking the above lock. So the + * rb_root must only be read/written after taking the above lock + * to be sure to see a valid next pointer. The LSB bit itself + * is serialized by a system wide lock only visible to + * mm_take_all_locks() (mm_all_locks_mutex). + */ + + /* Interval tree of private "related" vmas */ + struct rb_root_cached rb_root; +}; + +/* + * The copy-on-write semantics of fork mean that an anon_vma + * can become associated with multiple processes. Furthermore, + * each child process will have its own anon_vma, where new + * pages for that process are instantiated. + * + * This structure allows us to find the anon_vmas associated + * with a VMA, or the VMAs associated with an anon_vma. + * The "same_vma" list contains the anon_vma_chains linking + * all the anon_vmas associated with this VMA. + * The "rb" field indexes on an interval tree the anon_vma_chains + * which link all the VMAs associated with this anon_vma. + */ +struct anon_vma_chain { + struct vm_area_struct *vma; + struct anon_vma *anon_vma; + struct list_head same_vma; /* locked by mmap_lock & page_table_lock */ + struct rb_node rb; /* locked by anon_vma->rwsem */ + unsigned long rb_subtree_last; +#ifdef CONFIG_DEBUG_VM_RB + unsigned long cached_vma_start, cached_vma_last; +#endif +}; + +enum ttu_flags { + TTU_SPLIT_HUGE_PMD = 0x4, /* split huge PMD if any */ + TTU_IGNORE_MLOCK = 0x8, /* ignore mlock */ + TTU_SYNC = 0x10, /* avoid racy checks with PVMW_SYNC */ + TTU_HWPOISON = 0x20, /* do convert pte to hwpoison entry */ + TTU_BATCH_FLUSH = 0x40, /* Batch TLB flushes where possible + * and caller guarantees they will + * do a final flush if necessary */ + TTU_RMAP_LOCKED = 0x80, /* do not grab rmap lock: + * caller holds it */ +}; + +#ifdef CONFIG_MMU +static inline void get_anon_vma(struct anon_vma *anon_vma) +{ + atomic_inc(&anon_vma->refcount); +} + +void __put_anon_vma(struct anon_vma *anon_vma); + +static inline void put_anon_vma(struct anon_vma *anon_vma) +{ + if (atomic_dec_and_test(&anon_vma->refcount)) + __put_anon_vma(anon_vma); +} + +static inline void anon_vma_lock_write(struct anon_vma *anon_vma) +{ + down_write(&anon_vma->root->rwsem); +} + +static inline void anon_vma_unlock_write(struct anon_vma *anon_vma) +{ + up_write(&anon_vma->root->rwsem); +} + +static inline void anon_vma_lock_read(struct anon_vma *anon_vma) +{ + down_read(&anon_vma->root->rwsem); +} + +static inline int anon_vma_trylock_read(struct anon_vma *anon_vma) +{ + return down_read_trylock(&anon_vma->root->rwsem); +} + +static inline void anon_vma_unlock_read(struct anon_vma *anon_vma) +{ + up_read(&anon_vma->root->rwsem); +} + + +/* + * anon_vma helper functions. + */ +void anon_vma_init(void); /* create anon_vma_cachep */ +int __anon_vma_prepare(struct vm_area_struct *); +void unlink_anon_vmas(struct vm_area_struct *); +int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *); +int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *); + +static inline int anon_vma_prepare(struct vm_area_struct *vma) +{ + if (likely(vma->anon_vma)) + return 0; + + return __anon_vma_prepare(vma); +} + +static inline void anon_vma_merge(struct vm_area_struct *vma, + struct vm_area_struct *next) +{ + VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma); + unlink_anon_vmas(next); +} + +struct anon_vma *folio_get_anon_vma(struct folio *folio); + +/* RMAP flags, currently only relevant for some anon rmap operations. */ +typedef int __bitwise rmap_t; + +/* + * No special request: if the page is a subpage of a compound page, it is + * mapped via a PTE. The mapped (sub)page is possibly shared between processes. + */ +#define RMAP_NONE ((__force rmap_t)0) + +/* The (sub)page is exclusive to a single process. */ +#define RMAP_EXCLUSIVE ((__force rmap_t)BIT(0)) + +/* + * The compound page is not mapped via PTEs, but instead via a single PMD and + * should be accounted accordingly. + */ +#define RMAP_COMPOUND ((__force rmap_t)BIT(1)) + +/* + * rmap interfaces called when adding or removing pte of page + */ +void page_move_anon_rmap(struct page *, struct vm_area_struct *); +void page_add_anon_rmap(struct page *, struct vm_area_struct *, + unsigned long address, rmap_t flags); +void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, + unsigned long address); +void page_add_file_rmap(struct page *, struct vm_area_struct *, + bool compound); +void page_remove_rmap(struct page *, struct vm_area_struct *, + bool compound); + +void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *, + unsigned long address, rmap_t flags); +void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *, + unsigned long address); + +static inline void __page_dup_rmap(struct page *page, bool compound) +{ + atomic_inc(compound ? compound_mapcount_ptr(page) : &page->_mapcount); +} + +static inline void page_dup_file_rmap(struct page *page, bool compound) +{ + __page_dup_rmap(page, compound); +} + +/** + * page_try_dup_anon_rmap - try duplicating a mapping of an already mapped + * anonymous page + * @page: the page to duplicate the mapping for + * @compound: the page is mapped as compound or as a small page + * @vma: the source vma + * + * The caller needs to hold the PT lock and the vma->vma_mm->write_protect_seq. + * + * Duplicating the mapping can only fail if the page may be pinned; device + * private pages cannot get pinned and consequently this function cannot fail. + * + * If duplicating the mapping succeeds, the page has to be mapped R/O into + * the parent and the child. It must *not* get mapped writable after this call. + * + * Returns 0 if duplicating the mapping succeeded. Returns -EBUSY otherwise. + */ +static inline int page_try_dup_anon_rmap(struct page *page, bool compound, + struct vm_area_struct *vma) +{ + VM_BUG_ON_PAGE(!PageAnon(page), page); + + /* + * No need to check+clear for already shared pages, including KSM + * pages. + */ + if (!PageAnonExclusive(page)) + goto dup; + + /* + * If this page may have been pinned by the parent process, + * don't allow to duplicate the mapping but instead require to e.g., + * copy the page immediately for the child so that we'll always + * guarantee the pinned page won't be randomly replaced in the + * future on write faults. + */ + if (likely(!is_device_private_page(page)) && + unlikely(page_needs_cow_for_dma(vma, page))) + return -EBUSY; + + ClearPageAnonExclusive(page); + /* + * It's okay to share the anon page between both processes, mapping + * the page R/O into both processes. + */ +dup: + __page_dup_rmap(page, compound); + return 0; +} + +/** + * page_try_share_anon_rmap - try marking an exclusive anonymous page possibly + * shared to prepare for KSM or temporary unmapping + * @page: the exclusive anonymous page to try marking possibly shared + * + * The caller needs to hold the PT lock and has to have the page table entry + * cleared/invalidated. + * + * This is similar to page_try_dup_anon_rmap(), however, not used during fork() + * to duplicate a mapping, but instead to prepare for KSM or temporarily + * unmapping a page (swap, migration) via page_remove_rmap(). + * + * Marking the page shared can only fail if the page may be pinned; device + * private pages cannot get pinned and consequently this function cannot fail. + * + * Returns 0 if marking the page possibly shared succeeded. Returns -EBUSY + * otherwise. + */ +static inline int page_try_share_anon_rmap(struct page *page) +{ + VM_BUG_ON_PAGE(!PageAnon(page) || !PageAnonExclusive(page), page); + + /* device private pages cannot get pinned via GUP. */ + if (unlikely(is_device_private_page(page))) { + ClearPageAnonExclusive(page); + return 0; + } + + /* + * We have to make sure that when we clear PageAnonExclusive, that + * the page is not pinned and that concurrent GUP-fast won't succeed in + * concurrently pinning the page. + * + * Conceptually, PageAnonExclusive clearing consists of: + * (A1) Clear PTE + * (A2) Check if the page is pinned; back off if so. + * (A3) Clear PageAnonExclusive + * (A4) Restore PTE (optional, but certainly not writable) + * + * When clearing PageAnonExclusive, we cannot possibly map the page + * writable again, because anon pages that may be shared must never + * be writable. So in any case, if the PTE was writable it cannot + * be writable anymore afterwards and there would be a PTE change. Only + * if the PTE wasn't writable, there might not be a PTE change. + * + * Conceptually, GUP-fast pinning of an anon page consists of: + * (B1) Read the PTE + * (B2) FOLL_WRITE: check if the PTE is not writable; back off if so. + * (B3) Pin the mapped page + * (B4) Check if the PTE changed by re-reading it; back off if so. + * (B5) If the original PTE is not writable, check if + * PageAnonExclusive is not set; back off if so. + * + * If the PTE was writable, we only have to make sure that GUP-fast + * observes a PTE change and properly backs off. + * + * If the PTE was not writable, we have to make sure that GUP-fast either + * detects a (temporary) PTE change or that PageAnonExclusive is cleared + * and properly backs off. + * + * Consequently, when clearing PageAnonExclusive(), we have to make + * sure that (A1), (A2)/(A3) and (A4) happen in the right memory + * order. In GUP-fast pinning code, we have to make sure that (B3),(B4) + * and (B5) happen in the right memory order. + * + * We assume that there might not be a memory barrier after + * clearing/invalidating the PTE (A1) and before restoring the PTE (A4), + * so we use explicit ones here. + */ + + /* Paired with the memory barrier in try_grab_folio(). */ + if (IS_ENABLED(CONFIG_HAVE_FAST_GUP)) + smp_mb(); + + if (unlikely(page_maybe_dma_pinned(page))) + return -EBUSY; + ClearPageAnonExclusive(page); + + /* + * This is conceptually a smp_wmb() paired with the smp_rmb() in + * gup_must_unshare(). + */ + if (IS_ENABLED(CONFIG_HAVE_FAST_GUP)) + smp_mb__after_atomic(); + return 0; +} + +/* + * Called from mm/vmscan.c to handle paging out + */ +int folio_referenced(struct folio *, int is_locked, + struct mem_cgroup *memcg, unsigned long *vm_flags); + +void try_to_migrate(struct folio *folio, enum ttu_flags flags); +void try_to_unmap(struct folio *, enum ttu_flags flags); + +int make_device_exclusive_range(struct mm_struct *mm, unsigned long start, + unsigned long end, struct page **pages, + void *arg); + +/* Avoid racy checks */ +#define PVMW_SYNC (1 << 0) +/* Look for migration entries rather than present PTEs */ +#define PVMW_MIGRATION (1 << 1) + +struct page_vma_mapped_walk { + unsigned long pfn; + unsigned long nr_pages; + pgoff_t pgoff; + struct vm_area_struct *vma; + unsigned long address; + pmd_t *pmd; + pte_t *pte; + spinlock_t *ptl; + unsigned int flags; +}; + +#define DEFINE_PAGE_VMA_WALK(name, _page, _vma, _address, _flags) \ + struct page_vma_mapped_walk name = { \ + .pfn = page_to_pfn(_page), \ + .nr_pages = compound_nr(_page), \ + .pgoff = page_to_pgoff(_page), \ + .vma = _vma, \ + .address = _address, \ + .flags = _flags, \ + } + +#define DEFINE_FOLIO_VMA_WALK(name, _folio, _vma, _address, _flags) \ + struct page_vma_mapped_walk name = { \ + .pfn = folio_pfn(_folio), \ + .nr_pages = folio_nr_pages(_folio), \ + .pgoff = folio_pgoff(_folio), \ + .vma = _vma, \ + .address = _address, \ + .flags = _flags, \ + } + +static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw) +{ + /* HugeTLB pte is set to the relevant page table entry without pte_mapped. */ + if (pvmw->pte && !is_vm_hugetlb_page(pvmw->vma)) + pte_unmap(pvmw->pte); + if (pvmw->ptl) + spin_unlock(pvmw->ptl); +} + +bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw); + +/* + * Used by swapoff to help locate where page is expected in vma. + */ +unsigned long page_address_in_vma(struct page *, struct vm_area_struct *); + +/* + * Cleans the PTEs of shared mappings. + * (and since clean PTEs should also be readonly, write protects them too) + * + * returns the number of cleaned PTEs. + */ +int folio_mkclean(struct folio *); + +int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff, + struct vm_area_struct *vma); + +void remove_migration_ptes(struct folio *src, struct folio *dst, bool locked); + +int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma); + +/* + * rmap_walk_control: To control rmap traversing for specific needs + * + * arg: passed to rmap_one() and invalid_vma() + * try_lock: bail out if the rmap lock is contended + * contended: indicate the rmap traversal bailed out due to lock contention + * rmap_one: executed on each vma where page is mapped + * done: for checking traversing termination condition + * anon_lock: for getting anon_lock by optimized way rather than default + * invalid_vma: for skipping uninterested vma + */ +struct rmap_walk_control { + void *arg; + bool try_lock; + bool contended; + /* + * Return false if page table scanning in rmap_walk should be stopped. + * Otherwise, return true. + */ + bool (*rmap_one)(struct folio *folio, struct vm_area_struct *vma, + unsigned long addr, void *arg); + int (*done)(struct folio *folio); + struct anon_vma *(*anon_lock)(struct folio *folio, + struct rmap_walk_control *rwc); + bool (*invalid_vma)(struct vm_area_struct *vma, void *arg); +}; + +void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc); +void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc); +struct anon_vma *folio_lock_anon_vma_read(struct folio *folio, + struct rmap_walk_control *rwc); + +#else /* !CONFIG_MMU */ + +#define anon_vma_init() do {} while (0) +#define anon_vma_prepare(vma) (0) +#define anon_vma_link(vma) do {} while (0) + +static inline int folio_referenced(struct folio *folio, int is_locked, + struct mem_cgroup *memcg, + unsigned long *vm_flags) +{ + *vm_flags = 0; + return 0; +} + +static inline void try_to_unmap(struct folio *folio, enum ttu_flags flags) +{ +} + +static inline int folio_mkclean(struct folio *folio) +{ + return 0; +} +#endif /* CONFIG_MMU */ + +static inline int page_mkclean(struct page *page) +{ + return folio_mkclean(page_folio(page)); +} +#endif /* _LINUX_RMAP_H */ |