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cgroup: cgroup_escape takes no arguments

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cgroup_escape() is a slight abuse of the cgroup code: what we really want
here is to escape the *current* process, whether it happens to be the LXC
monitor or not, into the / cgroups.

In the case of dump, we can't do an lxc_init(), because:

lxc 20160310103501.547 ERROR    lxc_commands - commands.c:lxc_cmd_init:993 - ##
lxc 20160310103501.547 ERROR    lxc_commands - commands.c:lxc_cmd_init:994 - # The container appears to be already running!
lxc 20160310103501.547 ERROR    lxc_commands - commands.c:lxc_cmd_init:995 - ##

We don't want to make this a command to send to the handler, because again,
cgroup_escape() is intended to escape the *current* task to the root
cgroups.

So, let's just have cgroup_escape() build its own handler when required.

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
This commit is contained in:
Tycho Andersen 2016-03-10 11:10:14 -07:00
parent 9451eeffb0
commit 7103fe6f08
3 changed files with 19 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
src/lxc/cgfsng.c
View File

@ -1280,14 +1280,21 @@ static int cgfsng_nrtasks(void *hdata) {
}
/* Only root needs to escape to the cgroup of its init */
static bool cgfsng_escape(void *hdata)
static bool cgfsng_escape()
{
struct cgfsng_handler_data *d = hdata;
struct cgfsng_handler_data *d;
int i;
bool ret = false;
if (geteuid())
return true;
d = cgfsng_init("criu-temp-cgfsng");
if (!d) {
ERROR("cgfsng_init failed");
return false;
}
for (i = 0; d->hierarchies[i]; i++) {
char *fullpath = must_make_path(d->hierarchies[i]->mountpoint,
d->hierarchies[i]->base_cgroup,
@ -1295,12 +1302,15 @@ static bool cgfsng_escape(void *hdata)
if (lxc_write_to_file(fullpath, "0", 2, false) != 0) {
SYSERROR("Failed to escape to %s", fullpath);
free(fullpath);
return false;
goto out;
}
free(fullpath);
}
return true;
ret = true;
out:
free_handler_data(d);
return ret;
}
#define THAWED "THAWED"

4
src/lxc/cgroup.h
View File

@ -48,7 +48,7 @@ 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 *hdata);
bool (*escape)();
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);
@ -73,7 +73,7 @@ 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(struct lxc_handler *handler);
extern bool cgroup_escape();
/*
* Currently, this call only makes sense for privileged containers.

16
src/lxc/criu.c
View File

@ -63,7 +63,7 @@ static void exec_criu(struct criu_opts *opts)
* /actual/ root cgroup so that lxcfs thinks criu has enough rights to
* see all cgroups.
*/
if (!cgroup_escape(handler)) {
if (!cgroup_escape()) {
ERROR("failed to escape cgroups");
return;
}
@ -517,7 +517,7 @@ void do_restore(struct lxc_container *c, int pipe, char *directory, bool verbose
os.cgroup_path = cgroup_canonical_path(handler);
/* exec_criu() returning is an error */
exec_criu(handler, &os);
exec_criu(&os);
umount(rootfs->mount);
rmdir(rootfs->mount);
goto out_fini_handler;
@ -624,16 +624,6 @@ static bool do_dump(struct lxc_container *c, char *mode, char *directory,
if (pid == 0) {
struct criu_opts os;
struct lxc_handler *handler;
handler = lxc_init(c->name, c->lxc_conf, c->config_path);
if (!handler)
exit(1);
if (!cgroup_init(handler)) {
ERROR("failed initing cgroups");
exit(1);
}
os.action = mode;
os.directory = directory;
@ -643,7 +633,7 @@ static bool do_dump(struct lxc_container *c, char *mode, char *directory,
os.predump_dir = predump_dir;
/* exec_criu() returning is an error */
exec_criu(handler, &os);
exec_criu(&os);
exit(1);
} else {
int status;