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

[xuyang2018.jy@fujitsu.com]

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?

Best Regards
Yang Xu

>