cgroup: cgroup_escape takes no arguments

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>

diff --git a/src/lxc/cgfsng.c b/src/lxc/cgfsng.c
index 32213bf62a988b50236c5171849b4fa097180364..90b8358c150785b26e30e7a2b67811c04173a07b 100644 (file)
--- a/src/lxc/cgfsng.c
+++ b/src/lxc/cgfsng.c
@@ -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"

diff --git a/src/lxc/cgroup.h b/src/lxc/cgroup.h
index ff3651e4c0fed04a75494c16d5802f0404abae9d..e56a115edd9f154d05080894d4b511118fe4d3f4 100644 (file)
--- a/src/lxc/cgroup.h
+++ b/src/lxc/cgroup.h
@@ -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.

diff --git a/src/lxc/criu.c b/src/lxc/criu.c
index b4ebf420b52bc3fc050cb43fc1687fec6487fcb9..a683130f84a0d245d28609f904ab9b8503b774c8 100644 (file)
--- a/src/lxc/criu.c
+++ b/src/lxc/criu.c
@@ -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;