BUAA_OS_LAB 5 文件系统

课上

lab5-1 exam

从 rtc 态获取时间，并且实现用户态的进程休眠，比较简单。

注意读写外设系统调用的使用。

代码：

/**********user/include/lib.h**********/

u_int get_time(u_int *us);
void usleep(u_int us);

/*************user/lib/ipc.c***********/

u_int get_time(u_int *us) {
        u_int tmp = 0;
        u_int total = 0;
        u_int accur = 0;
        u_long RTC_ADDR = 0x15000000;
        u_long OFF0 = 0x0000;
        u_long OFF1 = 0x0010;
        u_long OFF2 = 0x0020;
        syscall_read_dev((void*)&tmp, RTC_ADDR + OFF0, 4);
        syscall_read_dev((void*)&total, RTC_ADDR + OFF1, 4);
        syscall_read_dev((void*)&accur, RTC_ADDR + OFF2, 4);
        *us = accur;
        return total;
}
void usleep(u_int us) {
        // 读取进程进入 usleep 函数的时间
        u_int total1;
        u_int us1;
        total1 = get_time(&us1);

        while (1) {
                // 读取当前时间
                u_int us2;
                u_int total2;
                total2 =  get_time(&us2);
                if ((u_long)total2 * 1000000 + us2 >= (u_long)total1 * 1000000 + us1 + us) {
                        return;
                } else {
                        // 进程切换
                        syscall_yield();
                }
        }
}

lab5-1 extra

模拟固态硬盘的管理，实现固态硬盘初始化、读写及擦除，重点是均匀磨损的实现。

没做出来，评测显示 ssd_read() 返回值错误，发现是擦除磁盘逻辑块对应物理块后未将其映射物理块设为空，非常可惜。

代码：

/***************fs/serv.h**************/

void ssd_init();
int ssd_read(u_int logic_no, void *dst);
void ssd_write(u_int logic_no, void *src);
void ssd_erase(u_int logic_no);

/***************fs/ide.c***************/

int flash_map[64];
int phy_bitmap;
int erase_cnt[64];

void era_phy(int id) {
        phy_bitmap |= (1 << id);
        erase_cnt[id]++; //add cnt when erase
        char arr[512];
        memset(arr, 0, sizeof(arr)); //all zero
        ide_write(0, id, (void*)arr, 1);
}

int alloc_phy() {
        int tar = -1;
        int cnt = -1;
        for (int i = 0; i < 32; ++i) {
                if (phy_bitmap & (1 << i)) {
                        if (tar == -1) {
                                tar = i;
                                cnt = erase_cnt[i];
                        } else {
                                if (cnt > erase_cnt[i]) {
                                        tar = i;
                                        cnt = erase_cnt[i];
                                }
                        }
                }
        }
        //panic_on(tar == -1);
        if (cnt >= 5) {
                int a = tar;
                tar = -1;
                cnt = -1;
                for (int i = 0; i < 32; ++i) {
                        if ((phy_bitmap & (1 << i)) == 0) {
                                if (tar == -1) {
                                        tar = i;
                                        cnt = erase_cnt[i];
                                } else {
                                        if (cnt > erase_cnt[i]) {
                                                tar = i;
                                                cnt = erase_cnt[i];
                                        }
                                }
                        }
                }
                //panic_on(tar == -1);
                int b = tar;
                char arr[512];
                ide_read(0, b, (void*)arr, 1);
                for (int j = 0; j <= 31; j++) {
                        if (flash_map[j] == b) {
                                flash_map[j] == a;
                                break;
                        }
                } //renew phy
                ide_write(0, a, (void*)arr, 1);
                phy_bitmap &= ~(1 << a); //a nwr
                phy_bitmap |= (1 << b); //b wr
                //era_phy(b);
                era_phy(b);
        } else {
        }

        return tar;

}

void ssd_init() {
        int total = 0;
        phy_bitmap = -1;
        memset(flash_map, -1, sizeof(flash_map)); //-1;
        memset(erase_cnt, 0, sizeof(erase_cnt));
}

int ssd_read(u_int logic_no, void *dst) {
        if (flash_map[logic_no] == -1) return -1;
        ide_read(0, flash_map[logic_no], dst, 1); //read
        return 0;
}

void ssd_write(u_int logic_no, void *src) {
        if (flash_map[logic_no] == -1) {

                flash_map[logic_no] = alloc_phy();
                phy_bitmap &= ~(1 << flash_map[logic_no]); //not writable
                ide_write(0, flash_map[logic_no], src, 1);
        } else {
                ssd_erase(logic_no);
                flash_map[logic_no] = alloc_phy();
                phy_bitmap &= ~(1 << flash_map[logic_no]); //not writable
                ide_write(0, flash_map[logic_no], src, 1); //read
        }
}

void ssd_erase(u_int logic_no) {
        if (flash_map[logic_no] == -1) return;
        era_phy(flash_map[logic_no]);
        flash_map[logic_no] = -1; //reset
}