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

[Richard Palethorpe]

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.

-- 
Thank you,
Richard.