[LTP] [PATCH v6 1/3] lib: alter find_free_loopdev()

Yang Xu
2019-07-30T10:42:10Z

> Hi!
>> +int tst_find_free_loopdev(const char *path, size_t path_len);
>> /*
>> * Reads test block device stat file and returns the bytes written since the
>> * last call of this function.
>> diff --git a/lib/tst_device.c b/lib/tst_device.c
>> index 65fcc1337..f2516fb08 100644
>> --- a/lib/tst_device.c
>> +++ b/lib/tst_device.c
>> @@ -53,22 +53,22 @@ static const char *dev_variants[] = {
>> "/dev/block/loop%i"
>> };
>>
>> -static int set_dev_path(int dev)
>> +static int set_dev_path(int dev, char *path, size_t path_len)
>> {
>> unsigned int i;
>> struct stat st;
>>
>> for (i = 0; i< ARRAY_SIZE(dev_variants); i++) {
>> - snprintf(dev_path, sizeof(dev_path), dev_variants[i], dev);
>> + snprintf(path, path_len, dev_variants[i], dev);
>>
>> - if (stat(dev_path,&st) == 0&& S_ISBLK(st.st_mode))
>> + if (stat(path,&st) == 0&& S_ISBLK(st.st_mode))
>> return 1;
>> }
>>
>> return 0;
>> }
>>
>> -static int find_free_loopdev(void)
>> +int tst_find_free_loopdev(char *path, size_t path_len)
>> {
>> int ctl_fd, dev_fd, rc, i;
>> struct loop_info loopinfo;
>> @@ -80,12 +80,14 @@ static int find_free_loopdev(void)
>> rc = ioctl(ctl_fd, LOOP_CTL_GET_FREE);
>> close(ctl_fd);
>> if (rc>= 0) {
>> - set_dev_path(rc);
>> - tst_resm(TINFO, "Found free device '%s'", dev_path);
>> - return 0;
>> + if (path)
>> + set_dev_path(rc, path, path_len);
>> + tst_resm(TINFO, "Found free device %d '%s'",
>> + rc, path ?: "");
>> + return rc;
>> }
>> tst_resm(TINFO, "Couldn't find free loop device");
>> - return 1;
>> + return -1;
>> }
>>
>> switch (errno) {
>> @@ -104,24 +106,24 @@ static int find_free_loopdev(void)
>> * Older way is to iterate over /dev/loop%i and /dev/loop/%i and try
>> * LOOP_GET_STATUS ioctl() which fails for free loop devices.
>> */
>> - for (i = 0; i< 256; i++) {
>> + for (i = 0; path&& i< 256; i++) {
> There is still a small problem here in the fallback code for older
> kernels. The way we detect a free device there is by opening the device
> and doing the LOOP_GET_STATUS ioctl(). So by disabling this loop if path
> is not set we broke the detection on older kernels when NULL is passed
> to the function.
>
> We should work with a local temporary path in this loop and copy it over
> to the path if we are succesfull and if path is not NULL.
>
Hi Cyril

Thanks for pointing out it. I will fix it on next version. as below:

int tst_find_free_loopdev(char *path, size_t path_len)
{
int ctl_fd, dev_fd, rc, i;
struct loop_info loopinfo;
+ char buf[1024];

/* since Linux 3.1 */
ctl_fd = open(LOOP_CONTROL_FILE, O_RDWR);
@@ -80,12 +81,14 @@ static int find_free_loopdev(void)
rc = ioctl(ctl_fd, LOOP_CTL_GET_FREE);
close(ctl_fd);
if (rc>= 0) {
- set_dev_path(rc);
- tst_resm(TINFO, "Found free device '%s'", dev_path);
- return 0;
+ if (path)
+ set_dev_path(rc, path, path_len);
+ tst_resm(TINFO, "Found free device %d '%s'",
+ rc, path ?: "");
+ return rc;
}
tst_resm(TINFO, "Couldn't find free loop device");
- return 1;
+ return -1;
}

static int find_free_loopdev(void)
*/
for (i = 0; i< 256; i++) {

- if (!set_dev_path(i))
+ if (!set_dev_path(i, buf, sizeof(buf)))
continue;

- dev_fd = open(dev_path, O_RDONLY);
+ dev_fd = open(buf, O_RDONLY);

if (dev_fd< 0)
continue;

if (ioctl(dev_fd, LOOP_GET_STATUS,&loopinfo) == 0) {
- tst_resm(TINFO, "Device '%s' in use", dev_path);
+ tst_resm(TINFO, "Device '%s' in use", buf);
} else {
if (errno != ENXIO)
continue;
- tst_resm(TINFO, "Found free device '%s'", dev_path);
+ tst_resm(TINFO, "Found free device '%s'", buf);
close(dev_fd);
- return 0;
+ if (path != NULL)
+ strcpy(path, buf);
+ return i;
}

Thanks
Yang Xu

>> - if (!set_dev_path(i))
>> + if (!set_dev_path(i, path, path_len))
>> continue;
>>
>> - dev_fd = open(dev_path, O_RDONLY);
>> + dev_fd = open(path, O_RDONLY);
>>
>> if (dev_fd< 0)
>> continue;
>>
>> if (ioctl(dev_fd, LOOP_GET_STATUS,&loopinfo) == 0) {
>> - tst_resm(TINFO, "Device '%s' in use", dev_path);
>> + tst_resm(TINFO, "Device '%s' in use", path);
>> } else {
>> if (errno != ENXIO)
>> continue;
>> - tst_resm(TINFO, "Found free device '%s'", dev_path);
>> + tst_resm(TINFO, "Found free device '%s'", path);
>> close(dev_fd);
>> - return 0;
>> + return i;
>> }
>>
>> close(dev_fd);
>> @@ -129,7 +131,7 @@ static int find_free_loopdev(void)
>>
>> tst_resm(TINFO, "No free devices found");
>>
>> - return 1;
>> + return -1;
>> }