问pwd和task_struct结构中的根有什么不同？

EN

struct task_struct {
/* these are hardcoded - don't touch */
        long state;     /* -1 unrunnable, 0 runnable, >0 stopped */
        long counter;
        long priority;
        long signal;
        struct sigaction sigaction[32];
        long blocked;   /* bitmap of masked signals */
/* various fields */
        int exit_code;
        unsigned long start_code,end_code,end_data,brk,start_stack;
        long pid,pgrp,session,leader;
        int     groups[NGROUPS];
        /* 
         * pointers to parent process, youngest child, younger sibling,
         * older sibling, respectively.  (p->father can be replaced with 
         * p->p_pptr->pid)
         */
        struct task_struct      *p_pptr, *p_cptr, *p_ysptr, *p_osptr;
        unsigned short uid,euid,suid;
        unsigned short gid,egid,sgid;
        unsigned long timeout,alarm;
        long utime,stime,cutime,cstime,start_time;
        struct rlimit rlim[RLIM_NLIMITS];
        unsigned int flags;     /* per process flags, defined below */
        unsigned short used_math;
/* file system info */
        int tty;                /* -1 if no tty, so it must be signed */
        unsigned short umask;
        struct m_inode * pwd;
        struct m_inode * root;
        struct m_inode * executable;
        struct m_inode * library;
        unsigned long close_on_exec;
        struct file * filp[NR_OPEN];
/* ldt for this task 0 - zero 1 - cs 2 - ds&ss */
        struct desc_struct ldt[3];
/* tss for this task */
        struct tss_struct tss;
};