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

Cyril Hrubis
2019-07-29T13:01:07Z

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.

> - 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;
> }

--
Cyril Hrubis
chrubis@suse.cz