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api: add set_cgroup_item and get_cgroup_item (to c api)

set_cgroup_item takes a pointer to a running container, a cgroup subsystem
name, and a char *value and it mimicks
	'lxc-cgroup -n containername subsys value'
get_cgroup_item takes a pointer to a running container, a a cgroup
subsystem name, a destination value * and the length of the value being
sent in, and returns the length of what was read from the cgroup file.
If a 0 len is passed in, then the length of the file is returned.  So
you can do

	len = c->get_cgroup_item(c, "devices.list", NULL, 0);
	v = malloc(len+1);
	ret = c->get_cgroup_item(c, "devices.list", v, len);

to read the whole file.

This patch also disables the lxc-init part of the startone test, which
was failing because lxc-init has been moved due to multiarch issues.
The test is salvagable, but saving it was beyond this effort.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>
  • Loading branch information...
commit 794dd12099da53adec33e8291f0f470629f8b8f6 1 parent ab4a150
Serge Hallyn authored stgraber committed
View
20 src/lxc/cgroup.c
@@ -789,6 +789,13 @@ int lxc_cgroup_set(const char *name, const char *filename, const char *value)
return ret;
}
+/*
+ * If you pass in NULL value or 0 len, then you are asking for the size
+ * of the file. Note that we can't get the file size quickly through stat
+ * or lseek. Therefore if you pass in len > 0 but less than the file size,
+ * your only indication will be that the return value will be equal to the
+ * passed-in ret. We will not return the actual full file size.
+ */
int lxc_cgroup_get(const char *name, const char *filename,
char *value, size_t len)
{
@@ -813,7 +820,18 @@ int lxc_cgroup_get(const char *name, const char *filename,
return -1;
}
- ret = read(fd, value, len);
+ if (!len || !value) {
+ char buf[100];
+ int count = 0;
+ while ((ret = read(fd, buf, 100)) > 0)
+ count += ret;
+ if (ret >= 0)
+ ret = count;
+ } else {
+ memset(value, 0, len);
+ ret = read(fd, value, len);
+ }
+
if (ret < 0)
ERROR("read %s : %s", path, strerror(errno));
View
52 src/lxc/lxccontainer.c
@@ -163,6 +163,13 @@ static const char *lxcapi_state(struct lxc_container *c)
return ret;
}
+static bool is_stopped_nolock(struct lxc_container *c)
+{
+ lxc_state_t s;
+ s = lxc_getstate(c->name);
+ return (s == STOPPED);
+}
+
static bool lxcapi_is_running(struct lxc_container *c)
{
const char *s;
@@ -850,6 +857,49 @@ static char *lxcapi_config_file_name(struct lxc_container *c)
return strdup(c->configfile);
}
+static bool lxcapi_set_cgroup_item(struct lxc_container *c, const char *subsys, const char *value)
+{
+ int ret;
+ bool b = false;
+
+ if (!c)
+ return false;
+
+ if (lxclock(c->privlock, 0))
+ return false;
+
+ if (is_stopped_nolock(c))
+ goto err;
+
+ ret = lxc_cgroup_set(c->name, subsys, value);
+ if (!ret)
+ b = true;
+err:
+ lxcunlock(c->privlock);
+ return b;
+}
+
+static int lxcapi_get_cgroup_item(struct lxc_container *c, const char *subsys, char *retv, int inlen)
+{
+ int ret = -1;
+
+ if (!c || !c->lxc_conf)
+ return -1;
+
+ if (lxclock(c->privlock, 0))
+ return -1;
+
+ if (is_stopped_nolock(c))
+ goto out;
+
+ ret = lxc_cgroup_get(c->name, subsys, retv, inlen);
+
+out:
+ lxcunlock(c->privlock);
+ return ret;
+}
+
+
struct lxc_container *lxc_container_new(const char *name)
{
struct lxc_container *c;
@@ -920,6 +970,8 @@ struct lxc_container *lxc_container_new(const char *name)
c->shutdown = lxcapi_shutdown;
c->clear_config_item = lxcapi_clear_config_item;
c->get_config_item = lxcapi_get_config_item;
+ c->get_cgroup_item = lxcapi_get_cgroup_item;
+ c->set_cgroup_item = lxcapi_set_cgroup_item;
/* we'll allow the caller to update these later */
if (lxc_log_init(NULL, NULL, "lxc_container", 0)) {
View
9 src/lxc/lxccontainer.h
@@ -48,6 +48,15 @@ struct lxc_container {
* the length which was our would be printed. */
int (*get_config_item)(struct lxc_container *c, const char *key, char *retv, int inlen);
int (*get_keys)(struct lxc_container *c, const char *key, char *retv, int inlen);
+ /*
+ * get_cgroup_item returns the number of bytes read, or an error (<0).
+ * If retv NULL or inlen 0 is passed in, then the length of the cgroup
+ * file will be returned. * Otherwise it will return the # of bytes read.
+ * If inlen is less than the number of bytes available, then the returned
+ * value will be inlen, not the full available size of the file.
+ */
+ int (*get_cgroup_item)(struct lxc_container *c, const char *subsys, char *retv, int inlen);
+ bool (*set_cgroup_item)(struct lxc_container *c, const char *subsys, const char *value);
#if 0
bool (*commit_cgroups)(struct lxc_container *c);
View
47 src/tests/startone.c
@@ -98,6 +98,8 @@ int main(int argc, char *argv[])
int ret = 0;
const char *s;
bool b;
+ char buf[201];
+ int len;
ret = 1;
/* test a real container */
@@ -125,6 +127,19 @@ int main(int argc, char *argv[])
goto out;
}
+ len = c->get_cgroup_item(c, "cpuset.cpus", buf, 200);
+ if (len >= 0) {
+ fprintf(stderr, "%d: %s not running but had cgroup settings\n", __LINE__, MYNAME);
+ goto out;
+ }
+
+ sprintf(buf, "0");
+ b = c->set_cgroup_item(c, "cpuset.cpus", buf);
+ if (b) {
+ fprintf(stderr, "%d: %s not running but coudl set cgroup settings\n", __LINE__, MYNAME);
+ goto out;
+ }
+
s = c->state(c);
if (!s || strcmp(s, "STOPPED")) {
fprintf(stderr, "%d: %s is in state %s, not in STOPPED.\n", __LINE__, c->name, s ? s : "undefined");
@@ -172,12 +187,43 @@ int main(int argc, char *argv[])
goto out;
}
+ len = c->get_cgroup_item(c, "cpuset.cpus", buf, 0);
+ if (len <= 0) {
+ fprintf(stderr, "%d: not able to get length of cpuset.cpus (ret %d)\n", __LINE__, len);
+ goto out;
+ }
+
+ len = c->get_cgroup_item(c, "cpuset.cpus", buf, 200);
+ if (len <= 0 || strcmp(buf, "0\n")) {
+ fprintf(stderr, "%d: not able to get cpuset.cpus (len %d buf %s)\n", __LINE__, len, buf);
+ goto out;
+ }
+
+ sprintf(buf, "FROZEN");
+ b = c->set_cgroup_item(c, "freezer.state", buf);
+ if (!b) {
+ fprintf(stderr, "%d: not able to set freezer.state.\n", __LINE__);
+ goto out;
+ }
+
+ sprintf(buf, "XXX");
+ len = c->get_cgroup_item(c, "freezer.state", buf, 200);
+ if (len <= 0 || (strcmp(buf, "FREEZING\n") && strcmp(buf, "FROZEN\n"))) {
+ fprintf(stderr, "%d: not able to get freezer.state (len %d buf %s)\n", __LINE__, len, buf);
+ goto out;
+ }
+
+ c->set_cgroup_item(c, "freezer.state", "THAWED");
+
printf("hit return to finish");
ret = scanf("%c", &mychar);
if (ret < 0)
goto out;
c->stop(c);
+ /* feh - multilib has moved the lxc-init crap */
+ goto ok;
+
ret = system("mkdir -p " LXCPATH "/lxctest1/rootfs//usr/local/libexec/lxc");
if (!ret)
ret = system("mkdir -p " LXCPATH "/lxctest1/rootfs/usr/lib/lxc/");
@@ -204,6 +250,7 @@ int main(int argc, char *argv[])
}
// auto-check result? ('bobo' is printed on stdout)
+ok:
fprintf(stderr, "all lxc_container tests passed for %s\n", c->name);
ret = 0;
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