mm: align struct page more aesthetically

[mirror_ubuntu-jammy-kernel.git] / include / linux / mm_types.h

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

#include <linux/mm_types_task.h>

#include <linux/auxvec.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/rbtree.h>
#include <linux/rwsem.h>
#include <linux/completion.h>
#include <linux/cpumask.h>
#include <linux/uprobes.h>
#include <linux/page-flags-layout.h>
#include <linux/workqueue.h>

#include <asm/mmu.h>

#ifndef AT_VECTOR_SIZE_ARCH
#define AT_VECTOR_SIZE_ARCH 0
#endif
#define AT_VECTOR_SIZE (2*(AT_VECTOR_SIZE_ARCH + AT_VECTOR_SIZE_BASE + 1))

struct address_space;
struct mem_cgroup;
struct hmm;

/*
 * Each physical page in the system has a struct page associated with
 * it to keep track of whatever it is we are using the page for at the
 * moment. Note that we have no way to track which tasks are using
 * a page, though if it is a pagecache page, rmap structures can tell us
 * who is mapping it.
 *
 * The objects in struct page are organized in double word blocks in
 * order to allows us to use atomic double word operations on portions
 * of struct page. That is currently only used by slub but the arrangement
 * allows the use of atomic double word operations on the flags/mapping
 * and lru list pointers also.
 */
#ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE
#define _struct_page_alignment  __aligned(2 * sizeof(unsigned long))
#else
#define _struct_page_alignment
#endif

struct page {
        /* First double word block */
        unsigned long flags;            /* Atomic flags, some possibly
                                         * updated asynchronously */
        union {
                struct address_space *mapping;  /* If low bit clear, points to
                                                 * inode address_space, or NULL.
                                                 * If page mapped as anonymous
                                                 * memory, low bit is set, and
                                                 * it points to anon_vma object
                                                 * or KSM private structure. See
                                                 * PAGE_MAPPING_ANON and
                                                 * PAGE_MAPPING_KSM.
                                                 */
                void *s_mem;                    /* slab first object */
                atomic_t compound_mapcount;     /* first tail page */
                /* page_deferred_list().next     -- second tail page */
        };

        /* Second double word */
        union {
                pgoff_t index;          /* Our offset within mapping. */
                void *freelist;         /* sl[aou]b first free object */
                /* page_deferred_list().prev    -- second tail page */
        };

        union {
#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
        defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
                /* Used for cmpxchg_double in slub */
                unsigned long counters;
#else
                /*
                 * Keep _refcount separate from slub cmpxchg_double data.
                 * As the rest of the double word is protected by slab_lock
                 * but _refcount is not.
                 */
                unsigned counters;
#endif
                struct {

                        union {
                                /*
                                 * Count of ptes mapped in mms, to show when
                                 * page is mapped & limit reverse map searches.
                                 *
                                 * Extra information about page type may be
                                 * stored here for pages that are never mapped,
                                 * in which case the value MUST BE <= -2.
                                 * See page-flags.h for more details.
                                 */
                                atomic_t _mapcount;

                                unsigned int active;            /* SLAB */
                                struct {                        /* SLUB */
                                        unsigned inuse:16;
                                        unsigned objects:15;
                                        unsigned frozen:1;
                                };
                                int units;                      /* SLOB */
                        };
                        /*
                         * Usage count, *USE WRAPPER FUNCTION* when manual
                         * accounting. See page_ref.h
                         */
                        atomic_t _refcount;
                };
        };

        /*
         * Third double word block
         *
         * WARNING: bit 0 of the first word encode PageTail(). That means
         * the rest users of the storage space MUST NOT use the bit to
         * avoid collision and false-positive PageTail().
         */
        union {
                struct list_head lru;   /* Pageout list, eg. active_list
                                         * protected by zone_lru_lock !
                                         * Can be used as a generic list
                                         * by the page owner.
                                         */
                struct dev_pagemap *pgmap; /* ZONE_DEVICE pages are never on an
                                            * lru or handled by a slab
                                            * allocator, this points to the
                                            * hosting device page map.
                                            */
                struct {                /* slub per cpu partial pages */
                        struct page *next;      /* Next partial slab */
#ifdef CONFIG_64BIT
                        int pages;      /* Nr of partial slabs left */
                        int pobjects;   /* Approximate # of objects */
#else
                        short int pages;
                        short int pobjects;
#endif
                };

                struct rcu_head rcu_head;       /* Used by SLAB
                                                 * when destroying via RCU
                                                 */
                /* Tail pages of compound page */
                struct {
                        unsigned long compound_head; /* If bit zero is set */

                        /* First tail page only */
#ifdef CONFIG_64BIT
                        /*
                         * On 64 bit system we have enough space in struct page
                         * to encode compound_dtor and compound_order with
                         * unsigned int. It can help compiler generate better or
                         * smaller code on some archtectures.
                         */
                        unsigned int compound_dtor;
                        unsigned int compound_order;
#else
                        unsigned short int compound_dtor;
                        unsigned short int compound_order;
#endif
                };

#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && USE_SPLIT_PMD_PTLOCKS
                struct {
                        unsigned long __pad;    /* do not overlay pmd_huge_pte
                                                 * with compound_head to avoid
                                                 * possible bit 0 collision.
                                                 */
                        pgtable_t pmd_huge_pte; /* protected by page->ptl */
                };
#endif
        };

        /* Remainder is not double word aligned */
        union {
                unsigned long private;          /* Mapping-private opaque data:
                                                 * usually used for buffer_heads
                                                 * if PagePrivate set; used for
                                                 * swp_entry_t if PageSwapCache;
                                                 * indicates order in the buddy
                                                 * system if PG_buddy is set.
                                                 */
#if USE_SPLIT_PTE_PTLOCKS
#if ALLOC_SPLIT_PTLOCKS
                spinlock_t *ptl;
#else
                spinlock_t ptl;
#endif
#endif
                struct kmem_cache *slab_cache;  /* SL[AU]B: Pointer to slab */
        };

#ifdef CONFIG_MEMCG
        struct mem_cgroup *mem_cgroup;
#endif

        /*
         * On machines where all RAM is mapped into kernel address space,
         * we can simply calculate the virtual address. On machines with
         * highmem some memory is mapped into kernel virtual memory
         * dynamically, so we need a place to store that address.
         * Note that this field could be 16 bits on x86 ... ;)
         *
         * Architectures with slow multiplication can define
         * WANT_PAGE_VIRTUAL in asm/page.h
         */
#if defined(WANT_PAGE_VIRTUAL)
        void *virtual;                  /* Kernel virtual address (NULL if
                                           not kmapped, ie. highmem) */
#endif /* WANT_PAGE_VIRTUAL */

#ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
        int _last_cpupid;
#endif
} _struct_page_alignment;

#define PAGE_FRAG_CACHE_MAX_SIZE        __ALIGN_MASK(32768, ~PAGE_MASK)
#define PAGE_FRAG_CACHE_MAX_ORDER       get_order(PAGE_FRAG_CACHE_MAX_SIZE)

struct page_frag_cache {
        void * va;
#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
        __u16 offset;
        __u16 size;
#else
        __u32 offset;
#endif
        /* we maintain a pagecount bias, so that we dont dirty cache line
         * containing page->_refcount every time we allocate a fragment.
         */
        unsigned int            pagecnt_bias;
        bool pfmemalloc;
};

typedef unsigned long vm_flags_t;

/*
 * A region containing a mapping of a non-memory backed file under NOMMU
 * conditions.  These are held in a global tree and are pinned by the VMAs that
 * map parts of them.
 */
struct vm_region {
        struct rb_node  vm_rb;          /* link in global region tree */
        vm_flags_t      vm_flags;       /* VMA vm_flags */
        unsigned long   vm_start;       /* start address of region */
        unsigned long   vm_end;         /* region initialised to here */
        unsigned long   vm_top;         /* region allocated to here */
        unsigned long   vm_pgoff;       /* the offset in vm_file corresponding to vm_start */
        struct file     *vm_file;       /* the backing file or NULL */

        int             vm_usage;       /* region usage count (access under nommu_region_sem) */
        bool            vm_icache_flushed : 1; /* true if the icache has been flushed for
                                                * this region */
};

#ifdef CONFIG_USERFAULTFD
#define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) { NULL, })
struct vm_userfaultfd_ctx {
        struct userfaultfd_ctx *ctx;
};
#else /* CONFIG_USERFAULTFD */
#define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) {})
struct vm_userfaultfd_ctx {};
#endif /* CONFIG_USERFAULTFD */

/*
 * This struct defines a memory VMM memory area. There is one of these
 * per VM-area/task.  A VM area is any part of the process virtual memory
 * space that has a special rule for the page-fault handlers (ie a shared
 * library, the executable area etc).
 */
struct vm_area_struct {
        /* The first cache line has the info for VMA tree walking. */

        unsigned long vm_start;         /* Our start address within vm_mm. */
        unsigned long vm_end;           /* The first byte after our end address
                                           within vm_mm. */

        /* linked list of VM areas per task, sorted by address */
        struct vm_area_struct *vm_next, *vm_prev;

        struct rb_node vm_rb;

        /*
         * Largest free memory gap in bytes to the left of this VMA.
         * Either between this VMA and vma->vm_prev, or between one of the
         * VMAs below us in the VMA rbtree and its ->vm_prev. This helps
         * get_unmapped_area find a free area of the right size.
         */
        unsigned long rb_subtree_gap;

        /* Second cache line starts here. */

        struct mm_struct *vm_mm;        /* The address space we belong to. */
        pgprot_t vm_page_prot;          /* Access permissions of this VMA. */
        unsigned long vm_flags;         /* Flags, see mm.h. */

        /*
         * For areas with an address space and backing store,
         * linkage into the address_space->i_mmap interval tree.
         */
        struct {
                struct rb_node rb;
                unsigned long rb_subtree_last;
        } shared;

        /*
         * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
         * list, after a COW of one of the file pages.  A MAP_SHARED vma
         * can only be in the i_mmap tree.  An anonymous MAP_PRIVATE, stack
         * or brk vma (with NULL file) can only be in an anon_vma list.
         */
        struct list_head anon_vma_chain; /* Serialized by mmap_sem &
                                          * page_table_lock */
        struct anon_vma *anon_vma;      /* Serialized by page_table_lock */

        /* Function pointers to deal with this struct. */
        const struct vm_operations_struct *vm_ops;

        /* Information about our backing store: */
        unsigned long vm_pgoff;         /* Offset (within vm_file) in PAGE_SIZE
                                           units */
        struct file * vm_file;          /* File we map to (can be NULL). */
        void * vm_private_data;         /* was vm_pte (shared mem) */

        atomic_long_t swap_readahead_info;
#ifndef CONFIG_MMU
        struct vm_region *vm_region;    /* NOMMU mapping region */
#endif
#ifdef CONFIG_NUMA
        struct mempolicy *vm_policy;    /* NUMA policy for the VMA */
#endif
        struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
} __randomize_layout;

struct core_thread {
        struct task_struct *task;
        struct core_thread *next;
};

struct core_state {
        atomic_t nr_threads;
        struct core_thread dumper;
        struct completion startup;
};

struct kioctx_table;
struct mm_struct {
        struct vm_area_struct *mmap;            /* list of VMAs */
        struct rb_root mm_rb;
        u32 vmacache_seqnum;                   /* per-thread vmacache */
#ifdef CONFIG_MMU
        unsigned long (*get_unmapped_area) (struct file *filp,
                                unsigned long addr, unsigned long len,
                                unsigned long pgoff, unsigned long flags);
#endif
        unsigned long mmap_base;                /* base of mmap area */
        unsigned long mmap_legacy_base;         /* base of mmap area in bottom-up allocations */
#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
        /* Base adresses for compatible mmap() */
        unsigned long mmap_compat_base;
        unsigned long mmap_compat_legacy_base;
#endif
        unsigned long task_size;                /* size of task vm space */
        unsigned long highest_vm_end;           /* highest vma end address */
        pgd_t * pgd;

        /**
         * @mm_users: The number of users including userspace.
         *
         * Use mmget()/mmget_not_zero()/mmput() to modify. When this drops
         * to 0 (i.e. when the task exits and there are no other temporary
         * reference holders), we also release a reference on @mm_count
         * (which may then free the &struct mm_struct if @mm_count also
         * drops to 0).
         */
        atomic_t mm_users;

        /**
         * @mm_count: The number of references to &struct mm_struct
         * (@mm_users count as 1).
         *
         * Use mmgrab()/mmdrop() to modify. When this drops to 0, the
         * &struct mm_struct is freed.
         */
        atomic_t mm_count;

#ifdef CONFIG_MMU
        atomic_long_t pgtables_bytes;           /* PTE page table pages */
#endif
        int map_count;                          /* number of VMAs */

        spinlock_t page_table_lock;             /* Protects page tables and some counters */
        struct rw_semaphore mmap_sem;

        struct list_head mmlist;                /* List of maybe swapped mm's.  These are globally strung
                                                 * together off init_mm.mmlist, and are protected
                                                 * by mmlist_lock
                                                 */


        unsigned long hiwater_rss;      /* High-watermark of RSS usage */
        unsigned long hiwater_vm;       /* High-water virtual memory usage */

        unsigned long total_vm;         /* Total pages mapped */
        unsigned long locked_vm;        /* Pages that have PG_mlocked set */
        unsigned long pinned_vm;        /* Refcount permanently increased */
        unsigned long data_vm;          /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
        unsigned long exec_vm;          /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
        unsigned long stack_vm;         /* VM_STACK */
        unsigned long def_flags;
        unsigned long start_code, end_code, start_data, end_data;
        unsigned long start_brk, brk, start_stack;
        unsigned long arg_start, arg_end, env_start, env_end;

        unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */

        /*
         * Special counters, in some configurations protected by the
         * page_table_lock, in other configurations by being atomic.
         */
        struct mm_rss_stat rss_stat;

        struct linux_binfmt *binfmt;

        cpumask_var_t cpu_vm_mask_var;

        /* Architecture-specific MM context */
        mm_context_t context;

        unsigned long flags; /* Must use atomic bitops to access the bits */

        struct core_state *core_state; /* coredumping support */
#ifdef CONFIG_MEMBARRIER
        atomic_t membarrier_state;
#endif
#ifdef CONFIG_AIO
        spinlock_t                      ioctx_lock;
        struct kioctx_table __rcu       *ioctx_table;
#endif
#ifdef CONFIG_MEMCG
        /*
         * "owner" points to a task that is regarded as the canonical
         * user/owner of this mm. All of the following must be true in
         * order for it to be changed:
         *
         * current == mm->owner
         * current->mm != mm
         * new_owner->mm == mm
         * new_owner->alloc_lock is held
         */
        struct task_struct __rcu *owner;
#endif
        struct user_namespace *user_ns;

        /* store ref to file /proc/<pid>/exe symlink points to */
        struct file __rcu *exe_file;
#ifdef CONFIG_MMU_NOTIFIER
        struct mmu_notifier_mm *mmu_notifier_mm;
#endif
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
        pgtable_t pmd_huge_pte; /* protected by page_table_lock */
#endif
#ifdef CONFIG_CPUMASK_OFFSTACK
        struct cpumask cpumask_allocation;
#endif
#ifdef CONFIG_NUMA_BALANCING
        /*
         * numa_next_scan is the next time that the PTEs will be marked
         * pte_numa. NUMA hinting faults will gather statistics and migrate
         * pages to new nodes if necessary.
         */
        unsigned long numa_next_scan;

        /* Restart point for scanning and setting pte_numa */
        unsigned long numa_scan_offset;

        /* numa_scan_seq prevents two threads setting pte_numa */
        int numa_scan_seq;
#endif
        /*
         * An operation with batched TLB flushing is going on. Anything that
         * can move process memory needs to flush the TLB when moving a
         * PROT_NONE or PROT_NUMA mapped page.
         */
        atomic_t tlb_flush_pending;
#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
        /* See flush_tlb_batched_pending() */
        bool tlb_flush_batched;
#endif
        struct uprobes_state uprobes_state;
#ifdef CONFIG_HUGETLB_PAGE
        atomic_long_t hugetlb_usage;
#endif
        struct work_struct async_put_work;

#if IS_ENABLED(CONFIG_HMM)
        /* HMM needs to track a few things per mm */
        struct hmm *hmm;
#endif
} __randomize_layout;

extern struct mm_struct init_mm;

static inline void mm_init_cpumask(struct mm_struct *mm)
{
#ifdef CONFIG_CPUMASK_OFFSTACK
        mm->cpu_vm_mask_var = &mm->cpumask_allocation;
#endif
        cpumask_clear(mm->cpu_vm_mask_var);
}

/* Future-safe accessor for struct mm_struct's cpu_vm_mask. */
static inline cpumask_t *mm_cpumask(struct mm_struct *mm)
{
        return mm->cpu_vm_mask_var;
}

struct mmu_gather;
extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
                                unsigned long start, unsigned long end);
extern void tlb_finish_mmu(struct mmu_gather *tlb,
                                unsigned long start, unsigned long end);

static inline void init_tlb_flush_pending(struct mm_struct *mm)
{
        atomic_set(&mm->tlb_flush_pending, 0);
}

static inline void inc_tlb_flush_pending(struct mm_struct *mm)
{
        atomic_inc(&mm->tlb_flush_pending);
        /*
         * The only time this value is relevant is when there are indeed pages
         * to flush. And we'll only flush pages after changing them, which
         * requires the PTL.
         *
         * So the ordering here is:
         *
         *      atomic_inc(&mm->tlb_flush_pending);
         *      spin_lock(&ptl);
         *      ...
         *      set_pte_at();
         *      spin_unlock(&ptl);
         *
         *                              spin_lock(&ptl)
         *                              mm_tlb_flush_pending();
         *                              ....
         *                              spin_unlock(&ptl);
         *
         *      flush_tlb_range();
         *      atomic_dec(&mm->tlb_flush_pending);
         *
         * Where the increment if constrained by the PTL unlock, it thus
         * ensures that the increment is visible if the PTE modification is
         * visible. After all, if there is no PTE modification, nobody cares
         * about TLB flushes either.
         *
         * This very much relies on users (mm_tlb_flush_pending() and
         * mm_tlb_flush_nested()) only caring about _specific_ PTEs (and
         * therefore specific PTLs), because with SPLIT_PTE_PTLOCKS and RCpc
         * locks (PPC) the unlock of one doesn't order against the lock of
         * another PTL.
         *
         * The decrement is ordered by the flush_tlb_range(), such that
         * mm_tlb_flush_pending() will not return false unless all flushes have
         * completed.
         */
}

static inline void dec_tlb_flush_pending(struct mm_struct *mm)
{
        /*
         * See inc_tlb_flush_pending().
         *
         * This cannot be smp_mb__before_atomic() because smp_mb() simply does
         * not order against TLB invalidate completion, which is what we need.
         *
         * Therefore we must rely on tlb_flush_*() to guarantee order.
         */
        atomic_dec(&mm->tlb_flush_pending);
}

static inline bool mm_tlb_flush_pending(struct mm_struct *mm)
{
        /*
         * Must be called after having acquired the PTL; orders against that
         * PTLs release and therefore ensures that if we observe the modified
         * PTE we must also observe the increment from inc_tlb_flush_pending().
         *
         * That is, it only guarantees to return true if there is a flush
         * pending for _this_ PTL.
         */
        return atomic_read(&mm->tlb_flush_pending);
}

static inline bool mm_tlb_flush_nested(struct mm_struct *mm)
{
        /*
         * Similar to mm_tlb_flush_pending(), we must have acquired the PTL
         * for which there is a TLB flush pending in order to guarantee
         * we've seen both that PTE modification and the increment.
         *
         * (no requirement on actually still holding the PTL, that is irrelevant)
         */
        return atomic_read(&mm->tlb_flush_pending) > 1;
}

struct vm_fault;

struct vm_special_mapping {
        const char *name;       /* The name, e.g. "[vdso]". */

        /*
         * If .fault is not provided, this points to a
         * NULL-terminated array of pages that back the special mapping.
         *
         * This must not be NULL unless .fault is provided.
         */
        struct page **pages;

        /*
         * If non-NULL, then this is called to resolve page faults
         * on the special mapping.  If used, .pages is not checked.
         */
        int (*fault)(const struct vm_special_mapping *sm,
                     struct vm_area_struct *vma,
                     struct vm_fault *vmf);

        int (*mremap)(const struct vm_special_mapping *sm,
                     struct vm_area_struct *new_vma);
};

enum tlb_flush_reason {
        TLB_FLUSH_ON_TASK_SWITCH,
        TLB_REMOTE_SHOOTDOWN,
        TLB_LOCAL_SHOOTDOWN,
        TLB_LOCAL_MM_SHOOTDOWN,
        TLB_REMOTE_SEND_IPI,
        NR_TLB_FLUSH_REASONS,
};

 /*
  * A swap entry has to fit into a "unsigned long", as the entry is hidden
  * in the "index" field of the swapper address space.
  */
typedef struct {
        unsigned long val;
} swp_entry_t;

#endif /* _LINUX_MM_TYPES_H */