[LTP] [PATCH v2] syscalls/ioctl_loop05: Use correct blockdev to get logical_block_size

[Yang Xu]

Hi Jan


> 
> 
> ----- Original Message -----
>>
>> Using df cmd (df -T /tmp/xxxxx/test.img)to get the correct block dev.
> 
> What I had in mind was to take "df -T" as inspiration, not call it directly,
> but that could work too. See notes below.
> 
>> +static void find_backing_bdpath(char *buf)
>> +{
>> +	char line[PATH_MAX];
>> +	FILE *file;
>> +
>> +	file = SAFE_FOPEN("1.txt", "r");
>> +
>> +	while (fgets(line, sizeof(line), file) != NULL)
>> +		sscanf(line, "%s", buf);
> 
> This will take the last line of output, which can be a problem as some
> version align output differently. For example:
> 
> # df -T .
> Filesystem           Type 1K-blocks    Used Available Use% Mounted on
> /dev/mapper/vg_dhcp13579-lv_root
>                       ext4  46967160 3102232  41472456   7% /
> 
> can break output into two lines.
Yes.
> 
>> +	SAFE_FCLOSE(file);
>> +}
>> +
>>   static void setup(void)
>>   {
>> -	int fd;
>> -	struct stat buf;
>> +	char buf[100];
>> +	const char *const df_cmd[] = {"df", "-T", ".", NULL};
>>   
>>   	if (tst_fs_type(".") == TST_TMPFS_MAGIC)
>>   		tst_brk(TCONF, "tmpfd doesn't support O_DIRECT flag");
>> @@ -109,13 +122,6 @@ static void setup(void)
>>   	sprintf(sys_loop_diopath, "/sys/block/loop%d/loop/dio", dev_num);
>>   	tst_fill_file("test.img", 0, 1024, 1024);
>>   
>> -	fd = SAFE_OPEN("test.img", O_RDONLY);
>> -	SAFE_FSTAT(fd, &buf);
>> -	SAFE_CLOSE(fd);
>> -
>> -	logical_block_size = buf.st_blksize;
>> -	tst_res(TINFO, "backing dev logical_block_size is %d", logical_block_size);
>> -
>>   	tst_attach_device(dev_path, "test.img");
>>   	attach_flag = 1;
>>   	dev_fd = SAFE_OPEN(dev_path, O_RDWR);
>> @@ -130,13 +136,24 @@ static void setup(void)
>>   	 *   size of loop is bigger than the backing device's and the loop
>>   	 *   needn't transform transfer.
>>   	 */
>> -	TST_RETRY_FUNC(ioctl(dev_fd, LOOP_SET_BLOCK_SIZE, logical_block_size),
>> TST_RETVAL_EQ0);
>> +	SAFE_CMD(df_cmd, "1.txt", NULL);
> 
> This could be part of find_backing_bdpath() function.
Yes.
> 
> What I had in mind when I referred to df was something like:
>    stat("test.img", &statbuf);
>    SAFE_MKNOD("blkdev", S_IFBLK | S_IRWXU, statbuf.st_dev);
>    block_devfd = SAFE_OPEN("blkdev", O_RDWR);
> What do you think?
> 
Oh, yes, it is more easier (I have tried this). I will send a v3 for this.

ps: I think I can use this in my other loop patches for loop_configure 
ioctl.
> 
>