[LTP] [PATCH v4 1/3] lib: alter find_free_loopdev()

Cyril Hrubis
2019-07-10T13:57:11Z

Hi!
> Alter find_free_loopdev() to return the free loopdev minor
> (and -1 for no free loopdev) and then WE can safely use the
> minor number that find_free_loopdev() returned in test cases.
>
> Signed-off-by: Yang Xu <xuyang2018.jy@cn.fujitsu.com>
> Reviewed-by: Amir Goldstein <amir73il@gmail.com>
> ---
> doc/test-writing-guidelines.txt | 9 +++++++++
> include/tst_device.h | 6 ++++++
> lib/tst_device.c | 12 ++++++------
> 3 files changed, 21 insertions(+), 6 deletions(-)
>
> diff --git a/doc/test-writing-guidelines.txt b/doc/test-writing-guidelines.txt
> index c6d4e001d..887801e68 100644
> --- a/doc/test-writing-guidelines.txt
> +++ b/doc/test-writing-guidelines.txt
> @@ -1045,6 +1045,15 @@ IMPORTANT: All testcases should use 'tst_umount()' instead of 'umount(2)' to
> -------------------------------------------------------------------------------
> #include "tst_test.h"
>
> +int find_free_loopdev();

Once this is exported as public API it should be prefixed with tst_.

> -static int find_free_loopdev(void)
> +int find_free_loopdev(void)
> {
> int ctl_fd, dev_fd, rc, i;
> struct loop_info loopinfo;
> @@ -82,10 +82,10 @@ static int find_free_loopdev(void)
> if (rc >= 0) {
> set_dev_path(rc);
> tst_resm(TINFO, "Found free device '%s'", dev_path);
> - return 0;
> + return rc;
> }
> tst_resm(TINFO, "Couldn't find free loop device");
> - return 1;
> + return -1;
> }
>
> switch (errno) {
> @@ -121,7 +121,7 @@ static int find_free_loopdev(void)
> continue;
> tst_resm(TINFO, "Found free device '%s'", dev_path);
> close(dev_fd);
> - return 0;
> + return i;
> }
>
> close(dev_fd);
> @@ -129,7 +129,7 @@ static int find_free_loopdev(void)
>
> tst_resm(TINFO, "No free devices found");
>
> - return 1;
> + return -1;
> }

This needs more changes than this.

The problem here is that the function modifies dev_path which is
returned by tst_acquire_device() so if you call this function after
tst_acquire_device() it will rewrite the dev_path which means that the
test would end up with wrong device path in tst_device->dev.

I guess that the easiest solution would be changing the function to get
buffer parameter which, when non-NULL, is filled with the path.

I.e. the function prototype would became:

int tst_find_free_loopdev(char *path, size_t path_len);

And we would pass the dev_path inside of the tst_device.c and NULL from
the copy_file_range() tests.

--
Cyril Hrubis
chrubis@suse.cz