cgroups: support cgroups mounted in multiple places (v3)

(sorry for the extra traffic.)

With this patch, lxc works for me both with all cgroups mounted with
ns cgroup on /cgroup, and with libcgroup mounting all cgroups
separately.

To do this, instead of looking for one cgroup called 'lxc' or
otherwise taking the first cgroup we find, we actually create a
container in every mounted cgroup fs.  Right now it's done under the
root of each fs.  We may want to put that under lxc, or, better yet,
make that configurable.

Changelog:
  Michael H. Warfield: Handle the case where subsystem doesn't have '.'.
  Daniel Lezcano: clean up incorrect reentrant use of mntent helpers
  v3: use the rest of Daniel's cleanups

TODO: add a configurable directory name, 'lxc' by default, under which
      all lxc cgroups are created (i.e. /sys/fs/cgroup/lxc)

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Tested-by: Michael H. Warfield <mhw@WittsEnd.com>
This commit is contained in:
Serge E. Hallyn 2011-07-04 00:42:06 +02:00 committed by Daniel Lezcano
parent c840b37de8
commit bcbd102cba
5 changed files with 147 additions and 117 deletions

View File

@ -52,90 +52,49 @@ enum {
CGROUP_CLONE_CHILDREN,
};
static int get_cgroup_mount(const char *mtab, char *mnt)
static int get_cgroup_mount(const char *subsystem, char *mnt)
{
struct mntent *mntent;
FILE *file = NULL;
int err = -1;
struct mntent *mntent;
FILE *file = NULL;
file = setmntent(mtab, "r");
if (!file) {
SYSERROR("failed to open %s", mtab);
file = setmntent(MTAB, "r");
if (!file) {
SYSERROR("failed to open %s", MTAB);
return -1;
}
}
while ((mntent = getmntent(file))) {
while ((mntent = getmntent(file))) {
/* there is a cgroup mounted named "lxc" */
if (!strcmp(mntent->mnt_fsname, "lxc") &&
!strcmp(mntent->mnt_type, "cgroup")) {
if (strcmp(mntent->mnt_type, "cgroup"))
continue;
if (!subsystem || hasmntopt(mntent, subsystem)) {
strcpy(mnt, mntent->mnt_dir);
err = 0;
break;
fclose(file);
DEBUG("using cgroup mounted at '%s'", mnt);
return 0;
}
};
/* fallback to the first non-lxc cgroup found */
if (!strcmp(mntent->mnt_type, "cgroup") && err) {
strcpy(mnt, mntent->mnt_dir);
err = 0;
}
};
DEBUG("Failed to find cgroup for %s\n", subsystem ? subsystem : "(NULL)");
DEBUG("using cgroup mounted at '%s'", mnt);
fclose(file);
fclose(file);
return err;
return -1;
}
static int get_cgroup_flags(const char *mtab, int *flags)
static int get_cgroup_flags(struct mntent *mntent)
{
struct mntent *mntent;
FILE *file = NULL;
int err = -1;
int flags = 0;
file = setmntent(mtab, "r");
if (!file) {
SYSERROR("failed to open %s", mtab);
return -1;
}
*flags = 0;
if (hasmntopt(mntent, "ns"))
flags |= CGROUP_NS_CGROUP;
while ((mntent = getmntent(file))) {
if (hasmntopt(mntent, "clone_children"))
flags |= CGROUP_CLONE_CHILDREN;
/* there is a cgroup mounted named "lxc" */
if (!strcmp(mntent->mnt_fsname, "lxc") &&
!strcmp(mntent->mnt_type, "cgroup")) {
if (hasmntopt(mntent, "ns"))
*flags |= CGROUP_NS_CGROUP;
if (hasmntopt(mntent, "clone_children"))
*flags |= CGROUP_CLONE_CHILDREN;
err = 0;
break;
}
/* fallback to the first non-lxc cgroup found */
if (!strcmp(mntent->mnt_type, "cgroup") && err) {
if (hasmntopt(mntent, "ns"))
*flags |= CGROUP_NS_CGROUP;
if (hasmntopt(mntent, "clone_children"))
*flags |= CGROUP_CLONE_CHILDREN;
err = 0;
}
};
DEBUG("cgroup flags is 0x%x", *flags);
fclose(file);
return err;
DEBUG("cgroup %s has flags 0x%x", mntent->mnt_dir, flags);
return flags;
}
static int cgroup_rename_nsgroup(const char *mnt, const char *name, pid_t pid)
@ -199,19 +158,19 @@ static int cgroup_attach(const char *path, pid_t pid)
return ret;
}
int lxc_cgroup_create(const char *name, pid_t pid)
/*
* create a cgroup for the container in a particular subsystem.
* XXX TODO we will of course want to use cgroup_path{subsystem}/lxc/name,
* not just cgroup_path{subsystem}/name.
*/
static int lxc_one_cgroup_create(const char *name,
struct mntent *mntent, pid_t pid)
{
char cgmnt[MAXPATHLEN];
char cgname[MAXPATHLEN];
char clonechild[MAXPATHLEN];
int flags;
if (get_cgroup_mount(MTAB, cgmnt)) {
ERROR("cgroup is not mounted");
return -1;
}
snprintf(cgname, MAXPATHLEN, "%s/%s", cgmnt, name);
snprintf(cgname, MAXPATHLEN, "%s/%s", mntent->mnt_dir, name);
/*
* There is a previous cgroup, assume it is empty,
@ -222,18 +181,16 @@ int lxc_cgroup_create(const char *name, pid_t pid)
return -1;
}
if (get_cgroup_flags(MTAB, &flags)) {
SYSERROR("failed to get cgroup flags");
return -1;
}
flags = get_cgroup_flags(mntent);
/* We have the deprecated ns_cgroup subsystem */
if (flags & CGROUP_NS_CGROUP) {
WARN("using deprecated ns_cgroup");
return cgroup_rename_nsgroup(cgmnt, cgname, pid);
return cgroup_rename_nsgroup(mntent->mnt_dir, cgname, pid);
}
snprintf(clonechild, MAXPATHLEN, "%s/cgroup.clone_children", cgmnt);
snprintf(clonechild, MAXPATHLEN, "%s/cgroup.clone_children",
mntent->mnt_dir);
/* we check if the kernel has clone_children, at this point if there
* no clone_children neither ns_cgroup, that means the cgroup is mounted
@ -263,19 +220,49 @@ int lxc_cgroup_create(const char *name, pid_t pid)
return -1;
}
INFO("created cgroup '%s'", cgname);
return 0;
}
int lxc_cgroup_destroy(const char *name)
/*
* for each mounted cgroup, create a cgroup for the container
*/
int lxc_cgroup_create(const char *name, pid_t pid)
{
char cgmnt[MAXPATHLEN];
char cgname[MAXPATHLEN];
struct mntent *mntent;
FILE *file = NULL;
int err = -1;
if (get_cgroup_mount(MTAB, cgmnt)) {
ERROR("cgroup is not mounted");
file = setmntent(MTAB, "r");
if (!file) {
SYSERROR("failed to open %s", MTAB);
return -1;
}
while ((mntent = getmntent(file))) {
DEBUG("checking '%s' (%s)", mntent->mnt_dir, mntent->mnt_type);
if (!strcmp(mntent->mnt_type, "cgroup")) {
INFO("found cgroup mounted at '%s'", mntent->mnt_dir);
err = lxc_one_cgroup_create(name, mntent, pid);
if (err)
goto out;
}
};
out:
endmntent(file);
return err;
}
int lxc_one_cgroup_destroy(const char *cgmnt, const char *name)
{
char cgname[MAXPATHLEN];
snprintf(cgname, MAXPATHLEN, "%s/%s", cgmnt, name);
if (rmdir(cgname)) {
SYSERROR("failed to remove cgroup '%s'", cgname);
@ -287,37 +274,80 @@ int lxc_cgroup_destroy(const char *name)
return 0;
}
int lxc_cgroup_path_get(char **path, const char *name)
/*
* for each mounted cgroup, destroy the cgroup for the container
*/
int lxc_cgroup_destroy(const char *name)
{
static char cgroup[MAXPATHLEN];
static const char* cgroup_cached = 0;
static char buf[MAXPATHLEN];
struct mntent *mntent;
FILE *file = NULL;
int ret, err = -1;
if (!cgroup_cached) {
if (get_cgroup_mount(MTAB, cgroup)) {
ERROR("cgroup is not mounted");
return -1;
} else {
cgroup_cached = cgroup;
file = setmntent(MTAB, "r");
if (!file) {
SYSERROR("failed to open %s", MTAB);
return -1;
}
while ((mntent = getmntent(file))) {
if (!strcmp(mntent->mnt_type, "cgroup")) {
DEBUG("destroying %s %s\n", mntent->mnt_dir, name);
ret = lxc_one_cgroup_destroy(mntent->mnt_dir, name);
if (ret) {
fclose(file);
return ret;
}
err = 0;
}
}
snprintf(buf, MAXPATHLEN, "%s/%s", cgroup_cached, name);
*path = buf;
fclose(file);
return err;
}
/*
* lxc_cgroup_path_get: put into *path the pathname for
* %subsystem and cgroup %name. If %subsystem is NULL, then
* the first mounted cgroup will be used (for nr_tasks)
*/
int lxc_cgroup_path_get(char **path, const char *subsystem, const char *name)
{
static char buf[MAXPATHLEN];
static char retbuf[MAXPATHLEN];
/* what lxc_cgroup_set calls subsystem is actually the filename, i.e.
'devices.allow'. So for our purposee we trim it */
if (subsystem) {
snprintf(retbuf, MAXPATHLEN, "%s", subsystem);
char *s = index(retbuf, '.');
if (s)
*s = '\0';
DEBUG("%s: called for subsys %s name %s\n", __func__, retbuf, name);
}
if (get_cgroup_mount(subsystem ? retbuf : NULL, buf)) {
ERROR("cgroup is not mounted");
return -1;
}
snprintf(retbuf, MAXPATHLEN, "%s/%s", buf, name);
DEBUG("%s: returning %s for subsystem %s", __func__, retbuf, subsystem);
*path = retbuf;
return 0;
}
int lxc_cgroup_set(const char *name, const char *subsystem, const char *value)
int lxc_cgroup_set(const char *name, const char *filename, const char *value)
{
int fd, ret;
char *nsgroup;
char *dirpath;
char path[MAXPATHLEN];
ret = lxc_cgroup_path_get(&nsgroup, name);
ret = lxc_cgroup_path_get(&dirpath, filename, name);
if (ret)
return -1;
snprintf(path, MAXPATHLEN, "%s/%s", nsgroup, subsystem);
snprintf(path, MAXPATHLEN, "%s/%s", dirpath, filename);
fd = open(path, O_WRONLY);
if (fd < 0) {
@ -330,25 +360,25 @@ int lxc_cgroup_set(const char *name, const char *subsystem, const char *value)
ERROR("write %s : %s", path, strerror(errno));
goto out;
}
ret = 0;
out:
close(fd);
return ret;
}
int lxc_cgroup_get(const char *name, const char *subsystem,
int lxc_cgroup_get(const char *name, const char *filename,
char *value, size_t len)
{
int fd, ret = -1;
char *nsgroup;
char *dirpath;
char path[MAXPATHLEN];
ret = lxc_cgroup_path_get(&nsgroup, name);
ret = lxc_cgroup_path_get(&dirpath, filename, name);
if (ret)
return -1;
snprintf(path, MAXPATHLEN, "%s/%s", nsgroup, subsystem);
snprintf(path, MAXPATHLEN, "%s/%s", dirpath, filename);
fd = open(path, O_RDONLY);
if (fd < 0) {
@ -366,16 +396,16 @@ int lxc_cgroup_get(const char *name, const char *subsystem,
int lxc_cgroup_nrtasks(const char *name)
{
char *nsgroup;
char *dpath;
char path[MAXPATHLEN];
int pid, ret, count = 0;
FILE *file;
ret = lxc_cgroup_path_get(&nsgroup, name);
ret = lxc_cgroup_path_get(&dpath, NULL, name);
if (ret)
return -1;
snprintf(path, MAXPATHLEN, "%s/tasks", nsgroup);
snprintf(path, MAXPATHLEN, "%s/tasks", dpath);
file = fopen(path, "r");
if (!file) {

View File

@ -28,6 +28,6 @@
struct lxc_handler;
int lxc_cgroup_create(const char *name, pid_t pid);
int lxc_cgroup_destroy(const char *name);
int lxc_cgroup_path_get(char **path, const char *name);
int lxc_cgroup_path_get(char **path, const char *subsystem, const char *name);
int lxc_cgroup_nrtasks(const char *name);
#endif

View File

@ -45,7 +45,7 @@ static int freeze_unfreeze(const char *name, int freeze)
char tmpf[32];
int fd, ret;
ret = lxc_cgroup_path_get(&nsgroup, name);
ret = lxc_cgroup_path_get(&nsgroup, "freezer", name);
if (ret)
return -1;

View File

@ -114,22 +114,22 @@ extern lxc_state_t lxc_state(const char *name);
* Set a specified value for a specified subsystem. The specified
* subsystem must be fully specified, eg. "cpu.shares"
* @name : the name of the container
* @subsystem : the subsystem
* @filename : the cgroup attribute filename
* @value : the value to be set
* Returns 0 on success, < 0 otherwise
*/
extern int lxc_cgroup_set(const char *name, const char *subsystem, const char *value);
extern int lxc_cgroup_set(const char *name, const char *filename, const char *value);
/*
* Get a specified value for a specified subsystem. The specified
* subsystem must be fully specified, eg. "cpu.shares"
* @name : the name of the container
* @subsystem : the subsystem
* @filename : the cgroup attribute filename
* @value : the value to be set
* @len : the len of the value variable
* Returns the number of bytes read, < 0 on error
*/
extern int lxc_cgroup_get(const char *name, const char *subsystem,
extern int lxc_cgroup_get(const char *name, const char *filename,
char *value, size_t len);
/*

View File

@ -71,7 +71,7 @@ static int freezer_state(const char *name)
FILE *file;
int err;
err = lxc_cgroup_path_get(&nsgroup, name);
err = lxc_cgroup_path_get(&nsgroup, "freezer", name);
if (err)
return -1;