RT-Thread：在dfs中使用cat、cp等命令时拔掉U盘死机问题_rtthread dfs cat

一、问题现象

1、使用ls、cp、mv、cat、rm、mkdir、echo命令操作文件未结束之前拔掉U盘，自己写的自动卸载U盘程序会出现死机现象。

二、问题原因

1、每次进行文件操作需要用到互斥锁的，流程：文件系统上锁–文件操作–文件系统解锁。但是上述命令所调用的函数是没有使用互斥锁，操作文件的时候拔掉U盘触发dfs_unmount函数卸载U盘，最终现象为两个线程同时对U盘进行文件操作发生异常。

三、解决方案

1、加上互斥锁即可，系统中已经有现成dfs的互斥锁函数dfs_lock和dfs_unlock，调用即可。在ls、cp、mv、cat、rm、mkdir、echo所调用的函数前进行dfs_lock，调用完成后dfs_unlock就可以解决问题。
2、按照上述进行解决其实使用cat时，拔掉U盘虽然不会死机，但是仍然会有异常发生，具体我会在下一篇博文讲到。
修改后的代码，我就不一一截图，直接上修改过的函数，这些函数都是在msh.c。

int cmd_ls(int argc, char **argv)
{
    extern void ls(const char *pathname);

	dfs_lock();
    if (argc == 1)
    {
#ifdef DFS_USING_WORKDIR
        ls(working_directory);
#else
        ls("/");
#endif
    }
    else
    {
        ls(argv[1]);
    }

	dfs_unlock();
    return 0;
}

int cmd_cp(int argc, char **argv)
{
    void copy(const char *src, const char *dst);

	dfs_lock();
    if (argc != 3)
    {
        rt_kprintf("Usage: cp SOURCE DEST\n");
        rt_kprintf("Copy SOURCE to DEST.\n");
    }
    else
    {
        copy(argv[1], argv[2]);
    }

	dfs_unlock();
    return 0;
}

int cmd_mv(int argc, char **argv)
{
	int res = 0;
	
	dfs_lock();
    if (argc != 3)
    {
        rt_kprintf("Usage: mv SOURCE DEST\n");
        rt_kprintf("Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY.\n");
    }
    else
    {
        int fd;
        char *dest = RT_NULL;

        rt_kprintf("%s => %s\n", argv[1], argv[2]);

        fd = open(argv[2], O_DIRECTORY, 0);
        if (fd >= 0)
        {
            char *src;

            close(fd);

            /* it's a directory */
            dest = (char *)rt_malloc(DFS_PATH_MAX);
            if (dest == RT_NULL)
            {
                rt_kprintf("out of memory\n");
				res = -RT_ENOMEM;
                goto end;
            }

            src = argv[1] + rt_strlen(argv[1]);
            while (src != argv[1])
            {
                if (*src == '/') break;
                src --;
            }

            rt_snprintf(dest, DFS_PATH_MAX - 1, "%s/%s", argv[2], src);
        }
        else
        {
            fd = open(argv[2], O_RDONLY, 0);
            if (fd >= 0)
            {
                close(fd);

                unlink(argv[2]);
            }

            dest = argv[2];
        }

        rename(argv[1], dest);
        if (dest != RT_NULL && dest != argv[2]) rt_free(dest);
    }

	end:
	dfs_unlock();
    return res;
}

int cmd_cat(int argc, char **argv)
{
    int index;
    extern void cat(const char *filename);

	dfs_lock();
    if (argc == 1)
    {
        rt_kprintf("Usage: cat [FILE]...\n");
        rt_kprintf("Concatenate FILE(s)\n");
        goto end;
    }

    for (index = 1; index < argc; index ++)
    {
        cat(argv[index]);
    }

	end:
	dfs_unlock();
    return 0;
}

int cmd_rm(int argc, char **argv)
{
    int index, n;
    char f = 0, r = 0, v = 0;

	dfs_lock();
    if (argc == 1)
    {
        rt_kprintf("Usage: rm option(s) FILE...\n");
        rt_kprintf("Remove (unlink) the FILE(s).\n");
        goto end;
    }

    if (argv[1][0] == '-')
    {
        for (n = 0; argv[1][n]; n++)
        {
            switch (argv[1][n])
            {
                case 'f': f = 1; break;
                case 'r': r = 1; break;
                case 'v': v = 1; break;
                case '-': break;
                default:
                    rt_kprintf("Error: Bad option: %c\n", argv[1][n]);
					goto end;
            }
        }
        argc -= 1;
        argv = argv + 1;
    }

    for (index = 1; index < argc; index ++)
    {
        struct stat s;
        if (stat (argv[index], &s) == 0)
        {
            if (s.st_mode & S_IFDIR)
            {
                if (r == 0)
                    rt_kprintf("cannot remove '%s': Is a directory\n", argv[index]);
                else
                    directory_delete_for_msh(argv[index], f, v);
            }
            else if (s.st_mode & S_IFREG)
            {
                if (unlink(argv[index]) != 0)
                {
                    if (f == 0)
                        rt_kprintf("cannot remove '%s'\n", argv[index]);
                }
                else if (v)
                {
                    rt_kprintf("removed '%s'\n", argv[index]);
                }
            }
        }
        else if (f == 0)
        {
            rt_kprintf("cannot remove '%s': No such file or directory\n", argv[index]);
        }
    }
	
	end:
	dfs_unlock();
    return 0;
}

int cmd_mkdir(int argc, char **argv)
{
	dfs_lock();
    if (argc == 1)
    {
        rt_kprintf("Usage: mkdir [OPTION] DIRECTORY\n");
        rt_kprintf("Create the DIRECTORY, if they do not already exist.\n");
    }
    else
    {
        mkdir(argv[1], 0);
    }

	dfs_unlock();
    return 0;
}

int cmd_df(int argc, char** argv)
{
	dfs_lock();
    if (argc != 2)
    {
        df("/");
    }
    else
    {
        if ((strcmp(argv[1], "--help") == 0) || (strcmp(argv[1], "-h") == 0))
        {
            rt_kprintf("df [path]\n");
        }
        else
        {
            df(argv[1]);
        }
    }

	dfs_unlock();
    return 0;
}

int cmd_echo(int argc, char** argv)
{
	dfs_lock();
    if (argc == 2)
    {
        rt_kprintf("%s\n", argv[1]);
    }
    else if (argc == 3)
    {
        int fd;

        fd = open(argv[2], O_RDWR | O_APPEND | O_CREAT, 0);
        if (fd >= 0)
        {
            write (fd, argv[1], strlen(argv[1]));
            close(fd);
        }
        else
        {
            rt_kprintf("open file:%s failed!\n", argv[2]);
        }
    }
    else
    {
        rt_kprintf("Usage: echo \"string\" [filename]\n");
    }

	dfs_unlock();
    return 0;
}
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