watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQv/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center">

在虚拟地址空间中，仅仅有那些映射到物理存储空间的地址才是合法的地址空间。每一片合法的地址空间片段都相应一个独立的虚拟内存区域（VMA，virtual memory areas ）。而进程的进程地址空间就是由这些内存区域组成。

struct mm_struct {

    struct vm_area_struct * mmap;        /* list of VMAs */

    struct rb_root mm_rb;

    struct vm_area_struct * mmap_cache;    /* last find_vma result */

    unsigned long (*get_unmapped_area) (struct file *filp,

                unsigned long addr, unsigned long len,

                unsigned long pgoff, unsigned long flags);

    void (*unmap_area) (struct mm_struct *mm, unsigned long addr);

    unsigned long mmap_base;        /* base of mmap area */

    unsigned long task_size;        /* size of task vm space */

    unsigned long cached_hole_size;     /* if non-zero, the largest hole below free_area_cache */

    unsigned long free_area_cache;        /* first hole of size cached_hole_size or larger */

    pgd_t * pgd;

    atomic_t mm_users;            /* How many users with user space? */

    atomic_t mm_count;            /* How many references to "struct mm_struct" (users count as 1) */

    int map_count;                /* number of VMAs */

    struct rw_semaphore mmap_sem;

    spinlock_t page_table_lock;        /* Protects page tables and some counters */

    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

                         */

    /* Special counters, in some configurations protected by the

     * page_table_lock, in other configurations by being atomic.

     */

    mm_counter_t _file_rss;

    mm_counter_t _anon_rss;

    unsigned long hiwater_rss;    /* High-watermark of RSS usage */

    unsigned long hiwater_vm;    /* High-water virtual memory usage */

    unsigned long total_vm, locked_vm, shared_vm, exec_vm;

    unsigned long stack_vm, reserved_vm, def_flags, nr_ptes;

    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 */

    struct linux_binfmt *binfmt;

    cpumask_t cpu_vm_mask;

    /* Architecture-specific MM context */

    mm_context_t context;

    /* Swap token stuff */

    /*

     * Last value of global fault stamp as seen by this process.

     * In other words, this value gives an indication of how long

     * it has been since this task got the token.

     * Look at mm/thrash.c

     */

    unsigned int faultstamp;

    unsigned int token_priority;

    unsigned int last_interval;

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

    struct core_state *core_state; /* coredumping support */

#ifdef CONFIG_AIO

    spinlock_t        ioctx_lock;

    struct hlist_head    ioctx_list;

#endif

#ifdef CONFIG_MM_OWNER

    /*

     * "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 *owner;

#endif

#ifdef CONFIG_PROC_FS

    /* store ref to file /proc/<pid>/exe symlink points to */

    struct file *exe_file;

    unsigned long num_exe_file_vmas;

#endif

#ifdef CONFIG_MMU_NOTIFIER

    struct mmu_notifier_mm *mmu_notifier_mm;

#endif

};