[lxc-devel] [PATCH 1/3] cgroup: add cgroup_escape() call
Serge Hallyn
serge.hallyn at ubuntu.com
Wed Dec 9 02:58:20 UTC 2015
Quoting Tycho Andersen (tycho.andersen at canonical.com):
> We'll use this in the next patch to escape to the root cgroup before we
> exec criu.
>
> Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> ---
> src/lxc/cgfs.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
> src/lxc/cgmanager.c | 19 ++++++++++++++++---
> src/lxc/cgroup.c | 7 +++++++
> src/lxc/cgroup.h | 2 ++
> 4 files changed, 75 insertions(+), 3 deletions(-)
>
> diff --git a/src/lxc/cgfs.c b/src/lxc/cgfs.c
> index d65f2d7..94b3d87 100644
> --- a/src/lxc/cgfs.c
> +++ b/src/lxc/cgfs.c
> @@ -2343,6 +2343,55 @@ static const char *cgfs_canonical_path(void *hdata)
> return path;
> }
>
> +static bool cgfs_escape(void)
> +{
> + struct cgroup_meta_data *md;
> + int i;
> + bool ret = false;
> +
> + md = lxc_cgroup_load_meta();
> + if (!md)
> + return false;
> +
> + for (i = 1; i <= md->maximum_hierarchy; i++) {
> + struct cgroup_hierarchy *h = md->hierarchies[i];
> + struct cgroup_mount_point *mp;
> + char *tasks;
> + FILE *f;
> + int written;
> +
> + if (!h) {
> + WARN("not escaping hierarchy %d", i);
> + continue;
> + }
> +
> + mp = lxc_cgroup_find_mount_point(h, "/", true);
> + if (!mp)
> + goto out;
> +
> + tasks = cgroup_to_absolute_path(mp, "/", "tasks");
> + if (!tasks)
> + goto out;
> +
> + f = fopen(tasks, "a");
> + free(tasks);
> + if (!f)
> + goto out;
> +
> + written = fprintf(f, "%d\n", getpid());
> + fclose(f);
> + if (written < 0) {
> + SYSERROR("writing tasks failed\n");
> + goto out;
> + }
> + }
> +
> + ret = true;
> +out:
> + lxc_cgroup_put_meta(md);
> + return ret;
> +}
> +
> static bool cgfs_unfreeze(void *hdata)
> {
> struct cgfs_data *d = hdata;
> @@ -2408,6 +2457,7 @@ static struct cgroup_ops cgfs_ops = {
> .create_legacy = cgfs_create_legacy,
> .get_cgroup = cgfs_get_cgroup,
> .canonical_path = cgfs_canonical_path,
> + .escape = cgfs_escape,
> .get = lxc_cgroupfs_get,
> .set = lxc_cgroupfs_set,
> .unfreeze = cgfs_unfreeze,
> diff --git a/src/lxc/cgmanager.c b/src/lxc/cgmanager.c
> index 05df0da..04adc69 100644
> --- a/src/lxc/cgmanager.c
> +++ b/src/lxc/cgmanager.c
> @@ -312,13 +312,22 @@ static bool lxc_cgmanager_create(const char *controller, const char *cgroup_path
> * be in "/lxc/c1" rather than "/user/..../c1"
> * called internally with connection already open
> */
> -static bool lxc_cgmanager_escape(void)
> +static bool cgm_escape(void)
> {
> - bool ret = true;
> + bool ret = true, cgm_connected = false;
Sorry, can you rename this disconnect_cgm or cgm_needs_disconnect ?
Other than that,
Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>
> pid_t me = getpid();
> char **slist = subsystems;
> int i;
>
> + if (!cgroup_manager) {
> + if (!cgm_dbus_connect()) {
> + ERROR("Error connecting to cgroup manager");
> + return false;
> + }
> + cgm_connected = true;
> + }
> +
> +
> if (cgm_all_controllers_same)
> slist = subsystems_inone;
>
> @@ -335,6 +344,9 @@ static bool lxc_cgmanager_escape(void)
> }
> }
>
> + if (cgm_connected)
> + cgm_dbus_disconnect();
> +
> return ret;
> }
>
> @@ -1307,7 +1319,7 @@ struct cgroup_ops *cgm_ops_init(void)
> goto err1;
>
> // root; try to escape to root cgroup
> - if (geteuid() == 0 && !lxc_cgmanager_escape())
> + if (geteuid() == 0 && !cgm_escape())
> goto err2;
> cgm_dbus_disconnect();
>
> @@ -1524,6 +1536,7 @@ static struct cgroup_ops cgmanager_ops = {
> .create_legacy = NULL,
> .get_cgroup = cgm_get_cgroup,
> .canonical_path = cgm_canonical_path,
> + .escape = cgm_escape,
> .get = cgm_get,
> .set = cgm_set,
> .unfreeze = cgm_unfreeze,
> diff --git a/src/lxc/cgroup.c b/src/lxc/cgroup.c
> index b1c764f..aeb8a58 100644
> --- a/src/lxc/cgroup.c
> +++ b/src/lxc/cgroup.c
> @@ -109,6 +109,13 @@ const char *cgroup_get_cgroup(struct lxc_handler *handler, const char *subsystem
> return NULL;
> }
>
> +bool cgroup_escape(void)
> +{
> + if (ops)
> + return ops->escape();
> + return false;
> +}
> +
> const char *cgroup_canonical_path(struct lxc_handler *handler)
> {
> if (geteuid()) {
> diff --git a/src/lxc/cgroup.h b/src/lxc/cgroup.h
> index 7704c04..e3d3ce4 100644
> --- a/src/lxc/cgroup.h
> +++ b/src/lxc/cgroup.h
> @@ -47,6 +47,7 @@ struct cgroup_ops {
> bool (*create_legacy)(void *hdata, pid_t pid);
> const char *(*get_cgroup)(void *hdata, const char *subsystem);
> const char *(*canonical_path)(void *hdata);
> + bool (*escape)(void);
> int (*set)(const char *filename, const char *value, const char *name, const char *lxcpath);
> int (*get)(const char *filename, char *value, size_t len, const char *name, const char *lxcpath);
> bool (*unfreeze)(void *hdata);
> @@ -71,6 +72,7 @@ extern void cgroup_cleanup(struct lxc_handler *handler);
> extern bool cgroup_create_legacy(struct lxc_handler *handler);
> extern int cgroup_nrtasks(struct lxc_handler *handler);
> extern const char *cgroup_get_cgroup(struct lxc_handler *handler, const char *subsystem);
> +extern bool cgroup_escape(void);
>
> /*
> * Currently, this call only makes sense for privileged containers.
> --
> 2.6.2
>
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