[lxc-devel] [PATCH] cgroupfs: cpuset support for kernels without cgroup.clone_children
Serge Hallyn
serge.hallyn at ubuntu.com
Tue Jan 28 16:32:30 UTC 2014
Quoting Robert Vogelgesang (vogel at users.sourceforge.net):
> Hi,
>
> as promised last week, here's my patch for cpuset cgroup support for
> kernels without the cgroup.clone_children feature.
Thanks.
> My initial patch used "#include <linux/version.h>" and the macros defined
> there to decide if cgroup.clone_children should be used or not. After
> having seen Serge Hallyn's patch which he posted to the list last Wednesday,
> where he used stat() to check if the cgroup.clone_children file is there,
> I rewrote my patch to do the same.
>
> The patch is against 1.0.0.beta3, and it is tested successfully with
> RHEL-6's kernel version 2.6.32-431.3.1.el6, compiled without cgmanager
Shouldn't be a problem as the cgfs_create function won't be called if
cgmanager is running.
> (I've so far not tried to use cgmanager in RHEL-6).
>
> In addition to fixing the cpuset cgroup setup, this patch also fixes a
> wrong argument in a call to handle_cgroup_settings() in the same context.
>
> Robert
>
> Signed-off-by: Robert Vogelgesang <vogel at users.sourceforge.net>
Just a two questions. I'll go ahead and run tests here while waiting
for an answer. If it comes down to "add the free and use 1024", I can
just do that inline.
Oh, in the future could you please add -p to your diff args? It makes
inline review just a touch easier.
> diff -u lxc-lxc-1.0.0.beta3/src/lxc/cgroup.c.cpuset2632 lxc-lxc-1.0.0.beta3/src/lxc/cgroup.c
> --- lxc-lxc-1.0.0.beta3/src/lxc/cgroup.c.cpuset2632 2014-01-27 14:52:20.000000000 +0100
> +++ lxc-lxc-1.0.0.beta3/src/lxc/cgroup.c 2014-01-27 16:50:11.000000000 +0100
> @@ -74,6 +74,7 @@
> static int cgroup_recursive_task_count(const char *cgroup_path);
> static int count_lines(const char *fn);
> static int handle_cgroup_settings(struct cgroup_mount_point *mp, char *cgroup_path);
> +static bool init_cpuset_if_needed(struct cgroup_mount_point *mp, const char *path);
>
> static struct cgroup_ops cgfs_ops;
> struct cgroup_ops *active_cg_ops = &cgfs_ops;
> @@ -897,15 +898,23 @@
> r = lxc_grow_array((void ***)&info_ptr->created_paths, &info_ptr->created_paths_capacity, info_ptr->created_paths_count + 1, 8);
> if (r < 0)
> goto cleanup_from_error;
> + if (!init_cpuset_if_needed(info_ptr->designated_mount_point, current_entire_path)) {
> + ERROR("Failed to initialize cpuset in new '%s'.", current_entire_path);
> + goto cleanup_from_error;
> + }
> info_ptr->created_paths[info_ptr->created_paths_count++] = current_entire_path;
> } else {
> /* if we didn't create the cgroup, then we have to make sure that
> * further cgroups will be created properly
> */
> - if (handle_cgroup_settings(mp, info_ptr->cgroup_path) < 0) {
> + if (handle_cgroup_settings(info_ptr->designated_mount_point, info_ptr->cgroup_path) < 0) {
> ERROR("Could not set clone_children to 1 for cpuset hierarchy in pre-existing cgroup.");
> goto cleanup_from_error;
> }
> + if (!init_cpuset_if_needed(info_ptr->designated_mount_point, info_ptr->cgroup_path)) {
> + ERROR("Failed to initialize cpuset in pre-existing '%s'.", info_ptr->cgroup_path);
> + goto cleanup_from_error;
> + }
>
> /* already existed but path component of pattern didn't contain '%n',
> * so this is not an error; but then we don't need current_entire_path
> @@ -2039,8 +2048,19 @@
> */
> if (lxc_string_in_array("cpuset", (const char **)mp->hierarchy->subsystems)) {
> char *cc_path = cgroup_to_absolute_path(mp, cgroup_path, "/cgroup.clone_children");
> + struct stat sb;
> +
> if (!cc_path)
> return -1;
> + /* cgroup.clone_children is not available when running under
> + * older kernel versions; in this case, we'll initialize
> + * cpuset.cpus and cpuset.mems later, after the new cgroup
> + * was created
> + */
> + if (stat(cc_path, &sb) != 0 && errno == ENOENT) {
> + free(cc_path);
> + return 0;
> + }
> r = lxc_read_from_file(cc_path, buf, 1);
> if (r == 1 && buf[0] == '1') {
> free(cc_path);
> @@ -2055,6 +2075,90 @@
> return 0;
> }
>
> +static bool cgroup_read_from_file(const char *fn, char buf[], size_t bufsize)
> +{
> + int ret = lxc_read_from_file(fn, buf, bufsize);
> + if (ret < 0) {
> + SYSERROR("failed to read %s", fn);
> + return false;
> + }
> + if (ret == bufsize) {
> + ERROR("too much data in %s", fn);
> + return false;
> + }
> + buf[ret] = '\0';
> + return true;
> +}
> +
> +static bool do_init_cpuset_file(struct cgroup_mount_point *mp,
> + const char *path, const char *name)
> +{
> + char value[128];
Is 128 enough? If some silly sod is running with just all the odd
cpus on a large system the file could get pretty big right?
> + char *childfile, *parentfile, *tmp;
> + bool ok;
> +
> + childfile = cgroup_to_absolute_path(mp, path, name);
> + if (!childfile)
> + return false;
> +
> + /* don't overwrite a non-empty value in the file */
> + if (!cgroup_read_from_file(childfile, value, sizeof(value))) {
> + free(childfile);
> + return false;
> + }
> + if (value[0] != '\0' && value[0] != '\n') {
> + free(childfile);
> + return true;
> + }
> +
> + /* path to the same name in the parent cgroup */
> + parentfile = strdup(path);
> + if (!parentfile)
childfile needs to be freed here?
> + return false;
> + tmp = strrchr(parentfile, '/');
> + if (!tmp) {
> + free(childfile);
> + free(parentfile);
> + return false;
> + }
> + if (tmp == parentfile)
> + tmp++; /* keep the '/' at the start */
> + *tmp = '\0';
> + tmp = parentfile;
> + parentfile = cgroup_to_absolute_path(mp, tmp, name);
> + free(tmp);
> + if (!parentfile) {
> + free(childfile);
> + return false;
> + }
> +
> + /* copy from parent to child cgroup */
> + if (!cgroup_read_from_file(parentfile, value, sizeof(value))) {
> + free(parentfile);
> + free(childfile);
> + return false;
> + }
> + ok = (lxc_write_to_file(childfile, value, strlen(value), false) >= 0);
> + if (!ok)
> + SYSERROR("failed writing %s", childfile);
> + free(parentfile);
> + free(childfile);
> +
> + return ok;
> +}
> +
> +static bool init_cpuset_if_needed(struct cgroup_mount_point *mp,
> + const char *path)
> +{
> + /* the files we have to handle here are only in cpuset hierarchies */
> + if (!lxc_string_in_array("cpuset",
> + (const char **)mp->hierarchy->subsystems))
> + return true;
> +
> + return (do_init_cpuset_file(mp, path, "/cpuset.cpus") &&
> + do_init_cpuset_file(mp, path, "/cpuset.mems") );
> +}
> +
> extern void lxc_monitor_send_state(const char *name, lxc_state_t state,
> const char *lxcpath);
> int do_unfreeze(int freeze, const char *name, const char *lxcpath)
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