On Wed, Nov 6, 2019 at 3:43 PM Tom Hromatka <tom.hroma...@oracle.com> wrote:
>
> This commit adds a function that, given a pid, can read in
> the controllers and cgroups listed in /proc/{pid}/cgroup.
> The caller is expected to allocate the controller_list[]
> and cgroup_list[] arrays as well as null each entry in the
> arrays. cg_get_cgroups_from_proc_cgroups() will allocate
> the necessary memory for each string within the arrays.
>
> Note that it's common to have many controllers on newer
> kernels, so MAX_MNT_ELEMENTS was increased to 16 to handle
> these additional controllers.
>
Gonna be pedantic and ask for another patch for that one, which can be
fast pathed in to the project.
Thanks!
Dhaval
> Signed-off-by: Tom Hromatka <tom.hroma...@oracle.com>
> ---
> src/api.c | 103
> +++++++++++++++++++++++++++++++++++++++++++++++
> src/libcgroup-internal.h | 2 +-
> 2 files changed, 104 insertions(+), 1 deletion(-)
>
> diff --git a/src/api.c b/src/api.c
> index 907475f8d6cf..105816a3ff51 100644
> --- a/src/api.c
> +++ b/src/api.c
> @@ -4189,6 +4189,109 @@ int cgroup_get_uid_gid_from_procfs(pid_t pid, uid_t
> *euid, gid_t *egid)
> }
>
> /**
> + * Given a pid, this function will return the controllers and cgroups that
> + * the pid is a member of. The caller is expected to allocate the
> + * controller_list[] and cgroup_list[] arrays as well as null each entry in
> + * the arrays. This function will allocate the necessary memory for each
> + * string within the arrays.
> + *
> + * @param pid The process id
> + * @param cgroup_list[] An array of char pointers to hold the cgroups
> + * @param controller_list[] An array of char pointers to hold the list
> + * of controllers
> + * @param list_len The size of the arrays
> + */
> +static int cg_get_cgroups_from_proc_cgroups(pid_t pid, char *cgroup_list[],
> + char *controller_list[],
> + int list_len)
> +{
> + char path[FILENAME_MAX];
> + char buf[4092];
> + char *stok_buff = NULL;
> + int ret = 0;
> + size_t buff_len;
> + int idx = 0;
> + FILE *f;
> +
> + sprintf(path, "/proc/%d/cgroup", pid);
> + f = fopen(path, "re");
> + if (!f)
> + return ECGROUPNOTEXIST;
> +
> + while (fgets(buf, sizeof(buf), f)) {
> + /*
> + * Each line in /proc/{pid}/cgroup is like the following:
> + *
> + * {cg#}:{controller}:{cgname}
> + *
> + * e.g.
> + * 7:devices:/user.slice
> + */
> +
> + /* read in the cgroup number. we don't care about it */
> + stok_buff = strtok(buf, ":");
> + /* read in the controller name */
> + stok_buff = strtok(NULL, ":");
> +
> + /*
> + * after this point, we have allocated memory. if we return
> + * an error code after this, it's up to us to free the
> + * memory we allocated
> + */
> + controller_list[idx] = strndup(stok_buff,
> + strlen(stok_buff) + 1);
> +
> + /* read in the cgroup name */
> + stok_buff = strtok(NULL, ":");
> +
> + if (stok_buff == NULL) {
> + /*
> + * An empty controller is reported on some kernels.
> + * It may look like this:
> + * 0::/user.slice/user-1000.slice/session-1.scope
> + *
> + * Ignore this controller and move on. Note that we
> + * need to free the controller list entry we made.
> + */
> + free(controller_list[idx]);
> + controller_list[idx] = NULL;
> + continue;
> + }
> +
> + buff_len = strlen(stok_buff);
> + if (stok_buff[buff_len - 1] == '\n')
> + /* Don't copy the trailing newline char */
> + buff_len--;
> +
> + /* read in the cgroup name */
> + if (buff_len > 1) {
> + /*
> + * Strip off the leading '/' for every cgroup but
> + * the root cgroup
> + */
> + cgroup_list[idx] = malloc(buff_len);
> + snprintf(cgroup_list[idx], buff_len, "%s",
> + &stok_buff[1]);
> + } else {
> + /*
> + * Retain the leading '/' since we're in the root
> + * cgroup
> + */
> + cgroup_list[idx] = strndup(stok_buff, buff_len);
> + }
> +
> + idx++;
> + if (idx >= list_len) {
> + cgroup_warn("Maximum mount elements reached. "
> + "Consider increasing MAX_MNT_ELEMENTS\n");
> + break;
> + }
> + }
> + fclose(f);
> + return ret;
> +}
> +
> +/**
> * Get process name from /proc/<pid>/status file.
> * @param pid: The process id
> * @param pname_status : The process name
> diff --git a/src/libcgroup-internal.h b/src/libcgroup-internal.h
> index e438916dafaf..b52c82c3f042 100644
> --- a/src/libcgroup-internal.h
> +++ b/src/libcgroup-internal.h
> @@ -28,7 +28,7 @@ __BEGIN_DECLS
> #include <setjmp.h>
>
> /* Maximum number of mount points/controllers */
> -#define MAX_MNT_ELEMENTS 8
> +#define MAX_MNT_ELEMENTS 16
> /* Estimated number of groups created */
> #define MAX_GROUP_ELEMENTS 128
>
> --
> 1.8.3.1
>
>
>
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