[lxc-devel] [PATCH 3/4] Automatic mounting: add more ways to mount the cgroup filesystem
Christian Seiler
christian at iwakd.de
Tue Sep 24 20:45:08 UTC 2013
This adds quite a few more ways to mount the cgroup filesystem
automatically:
- Specify ro/rw/mixed:
- ro: everything mounted read-only
- rw: everything mounted read-write
- mixed: only container's own cgroup is rw, rest ro
(default)
- Add cgroup-full that mounts the entire cgroup tree to the
corresponding directories. ro/rw/mixed also apply here.
Signed-off-by: Christian Seiler <christian at iwakd.de>
---
src/lxc/cgroup.c | 87 +++++++++++++++++++++++++++++++++++++++++++-----------
src/lxc/cgroup.h | 2 +-
src/lxc/conf.c | 2 +-
3 files changed, 71 insertions(+), 20 deletions(-)
diff --git a/src/lxc/cgroup.c b/src/lxc/cgroup.c
index 1270b8a..6025a4d 100644
--- a/src/lxc/cgroup.c
+++ b/src/lxc/cgroup.c
@@ -1215,7 +1215,7 @@ int lxc_setup_cgroup_devices(struct lxc_handler *h, struct lxc_list *cgroup_sett
return do_setup_cgroup(h, cgroup_settings, true);
}
-int lxc_setup_mount_cgroup(const char *root, struct cgroup_process_info *base_info)
+int lxc_setup_mount_cgroup(const char *root, struct cgroup_process_info *base_info, int type)
{
size_t bufsz = strlen(root) + sizeof("/sys/fs/cgroup");
char *path = NULL;
@@ -1226,6 +1226,12 @@ int lxc_setup_mount_cgroup(const char *root, struct cgroup_process_info *base_in
struct cgroup_process_info *info;
int r, saved_errno = 0;
+ if (type < LXC_AUTO_CGROUP_RO || type > LXC_AUTO_CGROUP_FULL_MIXED) {
+ ERROR("could not mount cgroups into container: invalid type specified internally");
+ errno = EINVAL;
+ return -1;
+ }
+
path = calloc(1, bufsz);
if (!path)
return -1;
@@ -1272,27 +1278,71 @@ int lxc_setup_mount_cgroup(const char *root, struct cgroup_process_info *base_in
goto out_error;
}
- /* create path for container's cgroup */
abs_path2 = lxc_append_paths(abs_path, info->cgroup_path);
if (!abs_path2)
goto out_error;
- r = mkdir_p(abs_path2, 0755);
- if (r < 0 && errno != EEXIST) {
- SYSERROR("could not create cgroup directory /sys/fs/cgroup/%s%s", dirname, info->cgroup_path);
- goto out_error;
- }
- free(abs_path);
- abs_path = NULL;
+ if (type == LXC_AUTO_CGROUP_FULL_RO || type == LXC_AUTO_CGROUP_FULL_RW || type == LXC_AUTO_CGROUP_FULL_MIXED) {
+ /* bind-mount the cgroup entire filesystem there */
+ if (strcmp(mp->mount_prefix, "/") != 0) {
+ /* FIXME: maybe we should just try to remount the entire hierarchy
+ * with a regular mount command? may that works? */
+ ERROR("could not automatically mount cgroup-full to /sys/fs/cgroup/%s: host has no mount point for this cgroup filesystem that has access to the root cgroup", dirname);
+ goto out_error;
+ }
+ r = mount(mp->mount_point, abs_path, "none", MS_BIND, 0);
+ if (r < 0) {
+ SYSERROR("error bind-mounting %s to %s", mp->mount_point, abs_path);
+ goto out_error;
+ }
+ /* main cgroup path should be read-only */
+ if (type == LXC_AUTO_CGROUP_FULL_RO || type == LXC_AUTO_CGROUP_FULL_MIXED) {
+ r = mount(NULL, abs_path, NULL, MS_REMOUNT|MS_BIND|MS_RDONLY, NULL);
+ if (r < 0) {
+ SYSERROR("error re-mounting %s readonly", abs_path);
+ goto out_error;
+ }
+ }
+ /* own cgroup should be read-write */
+ if (type == LXC_AUTO_CGROUP_FULL_MIXED) {
+ r = mount(abs_path2, abs_path2, NULL, MS_BIND, NULL);
+ if (r < 0) {
+ SYSERROR("error bind-mounting %s onto itself", abs_path2);
+ goto out_error;
+ }
+ r = mount(NULL, abs_path2, NULL, MS_REMOUNT|MS_BIND, NULL);
+ if (r < 0) {
+ SYSERROR("error re-mounting %s readwrite", abs_path2);
+ goto out_error;
+ }
+ }
+ } else {
+ /* create path for container's cgroup */
+ r = mkdir_p(abs_path2, 0755);
+ if (r < 0 && errno != EEXIST) {
+ SYSERROR("could not create cgroup directory /sys/fs/cgroup/%s%s", dirname, info->cgroup_path);
+ goto out_error;
+ }
- /* bind-mount container's cgroup to that directory */
- abs_path = cgroup_to_absolute_path(mp, info->cgroup_path, NULL);
- if (!abs_path)
- goto out_error;
- r = mount(abs_path, abs_path2, "none", MS_BIND, 0);
- if (r < 0) {
- SYSERROR("error bind-mounting %s to %s", abs_path, abs_path2);
- goto out_error;
+ free(abs_path);
+ abs_path = NULL;
+
+ /* bind-mount container's cgroup to that directory */
+ abs_path = cgroup_to_absolute_path(mp, info->cgroup_path, NULL);
+ if (!abs_path)
+ goto out_error;
+ r = mount(abs_path, abs_path2, "none", MS_BIND, 0);
+ if (r < 0) {
+ SYSERROR("error bind-mounting %s to %s", abs_path, abs_path2);
+ goto out_error;
+ }
+ if (type == LXC_AUTO_CGROUP_RO) {
+ r = mount(NULL, abs_path2, NULL, MS_REMOUNT|MS_BIND|MS_RDONLY, NULL);
+ if (r < 0) {
+ SYSERROR("error re-mounting %s readonly", abs_path2);
+ goto out_error;
+ }
+ }
}
free(abs_path);
@@ -1324,7 +1374,8 @@ int lxc_setup_mount_cgroup(const char *root, struct cgroup_process_info *base_in
* new cgroups outside the allowed area fails with an error instead
* of simply causing this to create directories in the tmpfs itself)
*/
- mount(NULL, path, NULL, MS_REMOUNT|MS_RDONLY, NULL);
+ if (type != LXC_AUTO_CGROUP_RW && type != LXC_AUTO_CGROUP_FULL_RW)
+ mount(NULL, path, NULL, MS_REMOUNT|MS_RDONLY, NULL);
free(path);
diff --git a/src/lxc/cgroup.h b/src/lxc/cgroup.h
index 5f517f6..0c0a678 100644
--- a/src/lxc/cgroup.h
+++ b/src/lxc/cgroup.h
@@ -160,7 +160,7 @@ struct lxc_list;
extern int lxc_setup_cgroup_without_devices(struct lxc_handler *h, struct lxc_list *cgroup_settings);
extern int lxc_setup_cgroup_devices(struct lxc_handler *h, struct lxc_list *cgroup_settings);
-extern int lxc_setup_mount_cgroup(const char *root, struct cgroup_process_info *base_info);
+extern int lxc_setup_mount_cgroup(const char *root, struct cgroup_process_info *base_info, int type);
extern int lxc_cgroup_nrtasks_handler(struct lxc_handler *handler);
diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index dd69a80..f35743f 100644
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -814,7 +814,7 @@ static int lxc_mount_auto_mounts(struct lxc_conf *conf, int flags, struct cgroup
}
if (flags & LXC_AUTO_CGROUP_MASK) {
- r = lxc_setup_mount_cgroup(conf->rootfs.mount, cgroup_info);
+ r = lxc_setup_mount_cgroup(conf->rootfs.mount, cgroup_info, flags & LXC_AUTO_CGROUP_MASK);
if (r < 0) {
SYSERROR("error mounting /sys/fs/cgroup");
return -1;
--
1.7.10.4
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