[LTP] [PATCH v1 2/3] tst_cgroup: Add safe_cg_open and safe_cg_fchown functions

[Richard Palethorpe]

Hello,

"xuyang2018.jy@fujitsu.com" <xuyang2018.jy@fujitsu.com> writes:

> Hi Richard
>> Hello,
>> 
>> Yang Xu <xuyang2018.jy@fujitsu.com> writes:
>> 
>>> safe_cg_open is used to open the sub control's file ie cgroup.procs
>>> and returns the fd.
>>>
>>> safe_cg_fchown is used to use fchownat to change file's uid and gid.
>>>
>>> Signed-off-by: Yang Xu <xuyang2018.jy@fujitsu.com>
>>> ---
>>>   include/tst_cgroup.h | 15 +++++++++++++++
>>>   lib/tst_cgroup.c     | 39 +++++++++++++++++++++++++++++++++++++++
>>>   2 files changed, 54 insertions(+)
>>>
>>> diff --git a/include/tst_cgroup.h b/include/tst_cgroup.h
>>> index d06847cc6..292c9baa4 100644
>>> --- a/include/tst_cgroup.h
>>> +++ b/include/tst_cgroup.h
>>> @@ -188,6 +188,21 @@ ssize_t safe_cg_read(const char *const file, const int lineno,
>>>   			 char *const out, const size_t len)
>>>   			 __attribute__ ((nonnull));
>>>   
>>> +#define SAFE_CG_OPEN(cg, file_name, flags)			\
>>> +	safe_cg_open(__FILE__, __LINE__, (cg), (file_name), (flags))
>>> +
>>> +int safe_cg_open(const char *const file, const int lineno,
>>> +		 const struct tst_cg_group *const cg,
>>> +		 const char *const file_name, int flags);
>>> +
>>> +#define SAFE_CG_FCHOWN(cg, file_name, owner, group)		\
>>> +	safe_cg_fchown(__FILE__, __LINE__,			\
>>> +			   (cg), (file_name), (owner), (group))
>>> +
>>> +void safe_cg_fchown(const char *const file, const int lineno,
>>> +		    const struct tst_cg_group *const cg,
>>> +		    const char *const file_name, uid_t owner, gid_t group);
>>> +
>>>   #define SAFE_CG_PRINTF(cg, file_name, fmt, ...)			\
>>>   	safe_cg_printf(__FILE__, __LINE__,				\
>>>   			   (cg), (file_name), (fmt), __VA_ARGS__)
>>> diff --git a/lib/tst_cgroup.c b/lib/tst_cgroup.c
>>> index 1cfd79243..dedc0f65b 100644
>>> --- a/lib/tst_cgroup.c
>>> +++ b/lib/tst_cgroup.c
>>> @@ -1297,6 +1297,45 @@ ssize_t safe_cg_read(const char *const file, const int lineno,
>>>   	return read_ret;
>>>   }
>>>   
>>> +int safe_cg_open(const char *const file, const int lineno,
>>> +			const struct tst_cg_group *cg,
>>> +			const char *const file_name, int flags)
>>> +{
>>> +	const struct cgroup_file *const cfile =
>>> +		cgroup_file_find(file, lineno, file_name);
>>> +	struct cgroup_dir *const *dir;
>>> +	const char *alias;
>>> +	int fd;
>>> +
>>> +	for_each_dir(cg, cfile->ctrl_indx, dir) {
>>> +		alias = cgroup_file_alias(cfile, *dir);
>>> +		if (!alias)
>>> +			continue;
>>> +
>>> +		fd = safe_openat(file, lineno, (*dir)->dir_fd, alias,
>>> flags);
>> 
>> This will only return the last fd that gets opened. That's OK if the
>> file only exists on a single V1 controller, but if it exists on multiple
>> controllers (e.g. any cgroup.* file) then we will open multiple files
>> and only return the fd for the last of them.
>
> Sorry for the late reply. I just copy these code from safe_cg_printf.
> So safe_cg_printf have the same situation that write value to muliple 
> files under the created cgroup directory.
>
> So what should we do? Add a fd arrat member in  cgroup_file  struct?

I'm not sure what you mean, but I can see a few options.

1. Pass a pointer to a function which takes the fd, for e.g.

safe_cg_open(..., void (*const on_open)(int fd))
{
        ...
        for_each_dir(...) {
            ...
            fd = safe_openat(...);
            on_open(fd);
            close(fd);
        }
        ...
}

2. Allocate and return an array of open fd's
3. Pass an array as large as the maximum number controllers which is
   populated with open fd's.

Which option to pick I think depends on what results in the simplest
test code.

>
> Best Regards
> Yang Xu
>
>> 


-- 
Thank you,
Richard.