Dan Smith wrote:
> This patch adds src/cgroup.{c,h} with support for creating and manipulating
> cgroups. It's quite naive at the moment, but should provide something to
> work with to move forward with resource controls.
>
> All groups created with the internal API are forced under $mount/libvirt/
> to keep everything together. The first time a group is created, the libvirt
> directory is also created, and the settings from the root are inherited.
>
> The code scans the mount table to look for the first mount of type cgroup,
> and assumes that all controllers are mounted there. I think this
> could/should be updated to prefer a mount with just the controller(s) we
> want, if there are multiple ones.
>
> If you have the cpuset controller enabled, and cpuset.cpus_exclusive is 1,
> then all cgroups to be created will fail. Since we probably shouldn't
> blindly set the root to be non-exclusive, we may also want to consider this
> condition to be "no cgroup support".
>
> diff -r 444e2614d0a2 -r 8e948eb88328 src/Makefile.am
> --- a/src/Makefile.am Wed Sep 17 16:07:03 2008 +0000
> +++ b/src/Makefile.am Mon Sep 29 09:37:42 2008 -0700
> @@ -96,7 +96,8 @@
> lxc_conf.c lxc_conf.h \
> lxc_container.c lxc_container.h \
> lxc_controller.c \
> - veth.c veth.h
> + veth.c veth.h \
> + cgroup.c cgroup.h
>
> OPENVZ_DRIVER_SOURCES = \
> openvz_conf.c openvz_conf.h \
> diff -r 444e2614d0a2 -r 8e948eb88328 src/cgroup.c
> --- /dev/null Thu Jan 01 00:00:00 1970 +0000
> +++ b/src/cgroup.c Mon Sep 29 09:37:42 2008 -0700
> @@ -0,0 +1,526 @@
> +/*
> + * cgroup.c: Tools for managing cgroups
> + *
> + * Copyright IBM Corp. 2008
> + *
> + * See COPYING.LIB for the License of this software
> + *
> + * Authors:
> + * Dan Smith <danms@xxxxxxxxxx>
> + */
> +#include <config.h>
> +
> +#include <stdio.h>
> +#include <stdint.h>
> +#include <inttypes.h>
> +#include <mntent.h>
> +#include <fcntl.h>
> +#include <string.h>
> +#include <errno.h>
> +#include <stdlib.h>
> +#include <stdbool.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +#include <libgen.h>
> +
> +#include "internal.h"
> +#include "util.h"
> +#include "cgroup.h"
> +
> +#define DEBUG(fmt,...) VIR_DEBUG(__FILE__, fmt, __VA_ARGS__)
> +#define DEBUG0(msg) VIR_DEBUG(__FILE__, "%s", msg)
> +
> +struct virCgroup {
> + char *path;
> +};
> +
There is no support for permissions, is everything run as root?
> +void virCgroupFree(virCgroupPtr *group)
> +{
> + if (*group != NULL) {
> + free((*group)->path);
> + free(*group);
> + *group = NULL;
> + }
> +}
> +
> +static virCgroupPtr cgroup_get_mount(void)
> +{
> + FILE *mounts;
> + struct mntent entry;
> + char buf[512];
Is 512 arbitrary? How do we know it is going to be sufficient?
> + virCgroupPtr root = NULL;
> +
> + root = calloc(1, sizeof(*root));
> + if (root == NULL)
> + return NULL;
> +
> + mounts = fopen("/proc/mounts", "r");
> + if (mounts == NULL) {
> + DEBUG0("Unable to open /proc/mounts: %m");
> + goto err;
> + }
> +
> + while (getmntent_r(mounts, &entry, buf, sizeof(buf)) != NULL) {
> + if (STREQ(entry.mnt_type, "cgroup")) {
> + root->path = strdup(entry.mnt_dir);
> + break;
> + }
> + }
> +
> + if (root->path == NULL) {
> + DEBUG0("Did not find cgroup mount");
Or strdup failed due to ENOMEM
> + goto err;
> + }
> +
> + fclose(mounts);
> +
> + return root;
> +err:
> + virCgroupFree(&root);
> +
> + return NULL;
> +}
> +
> +int virCgroupHaveSupport(void)
> +{
> + virCgroupPtr root;
> +
> + root = cgroup_get_mount();
> + if (root == NULL)
> + return -1;
> +
> + virCgroupFree(&root);
> +
This is quite a horrible way of wasting computation.
> + return 0;
> +}
> +
> +static int cgroup_path_of(const char *grppath,
> + const char *key,
> + char **path)
> +{
> + virCgroupPtr root;
> + int rc = 0;
> +
> + root = cgroup_get_mount();
So every routine calls cgroup_path_of(), reads the mounts entry and find a entry
for cgroup and returns it, why not do it just once and use it.
> + if (root == NULL) {
> + rc = -ENOTDIR;
> + goto out;
> + }
> +
> + if (asprintf(path, "%s/%s/%s", root->path, grppath, key) == -1)
> + rc = -ENOMEM;
> +out:
> + virCgroupFree(&root);
> +
> + return rc;
> +}
> +
> +int virCgroupSetValueStr(virCgroupPtr group,
> + const char *key,
> + const char *value)
> +{
> + int fd = -1;
> + int rc = 0;
> + char *keypath = NULL;
> +
> + rc = cgroup_path_of(group->path, key, &keypath);
> + if (rc != 0)
> + return rc;
> +
> + fd = open(keypath, O_WRONLY);
I see a mix of open and fopen calls.I would prefer to stick to just one, helps
with readability.
> + if (fd < 0) {
> + DEBUG("Unable to open %s: %m", keypath);
> + rc = -ENOENT;
> + goto out;
> + }
> +
> + DEBUG("Writing '%s' to '%s'", value, keypath);
> +
> + rc = safewrite(fd, value, strlen(value));
> + if (rc < 0) {
> + DEBUG("Failed to write value '%s': %m", value);
> + rc = -errno;
> + goto out;
> + } else if (rc != strlen(value)) {
> + DEBUG("Short write of value '%s'", value);
> + rc = -ENOSPC;
> + goto out;
> + }
> +
> + rc = 0;
> +out:
> + free(keypath);
> + close(fd);
> +
> + return rc;
> +}
> +
> +int virCgroupSetValueU64(virCgroupPtr group,
> + const char *key,
> + uint64_t value)
> +{
> + char *strval = NULL;
> + int rc;
> +
> + if (asprintf(&strval, "%" PRIu64, value) == -1)
> + return -ENOMEM;
> +
> + rc = virCgroupSetValueStr(group, key, strval);
> +
> + free(strval);
> +
> + return rc;
> +}
> +
> +int virCgroupSetValueI64(virCgroupPtr group,
> + const char *key,
> + int64_t value)
> +{
> + char *strval = NULL;
> + int rc;
> +
> + if (asprintf(&strval, "%" PRIi64, value) == -1)
> + return -ENOMEM;
> +
> + rc = virCgroupSetValueStr(group, key, strval);
> +
> + free(strval);
> +
> + return rc;
> +}
> +
> +int virCgroupGetValueStr(virCgroupPtr group,
> + const char *key,
> + char **value)
> +{
> + int fd = -1;
> + int rc;
> + char *keypath = NULL;
> + char buf[512];
> +
I don't think 512 bytes will be sufficient. THere are multi-line files like
memory.stat.
> + memset(buf, 0, sizeof(buf));
> +
> + rc = cgroup_path_of(group->path, key, &keypath);
> + if (rc != 0) {
> + DEBUG("No path of %s, %s", group->path, key);
> + return rc;
> + }
> +
> + fd = open(keypath, O_RDONLY);
> + if (fd < 0) {
> + DEBUG("Unable to open %s: %m", keypath);
> + rc = -ENOENT;
> + goto out;
> + }
> +
> + rc = saferead(fd, buf, sizeof(buf));
> + if (rc < 0) {
> + DEBUG("Failed to read %s: %m\n", keypath);
> + rc = -errno;
> + goto out;
> + } else if (rc == 0) {
> + DEBUG("Short read of %s\n", keypath);
> + rc = -EIO;
> + goto out;
> + }
> +
> + *value = strdup(buf);
> + if (*value == NULL) {
> + rc = -ENOMEM;
> + goto out;
> + }
> +
> + rc = 0;
> +out:
> + free(keypath);
> + close(fd);
> +
> + return rc;
> +}
> +
> +int virCgroupGetValueU64(virCgroupPtr group,
> + const char *key,
> + uint64_t *value)
> +{
> + char *strval = NULL;
> + int rc = 0;
> +
> + rc = virCgroupGetValueStr(group, key, &strval);
> + if (rc != 0)
> + goto out;
> +
> + if (sscanf(strval, "%" SCNu64, value) != 1)
> + rc = -EINVAL;
> +out:
> + free(strval);
> +
> + return rc;
> +}
> +
> +int virCgroupGetValueI64(virCgroupPtr group,
> + const char *key,
> + int64_t *value)
> +{
> + char *strval = NULL;
> + int rc = 0;
> +
> + rc = virCgroupGetValueStr(group, key, &strval);
> + if (rc != 0)
> + goto out;
> +
> + if (sscanf(strval, "%" SCNi64, value) != 1)
> + rc = -EINVAL;
> +out:
> + free(strval);
> +
> + return rc;
> +}
> +
> +int virCgroupHasValue(virCgroupPtr group,
> + const char *key)
> +{
> + int rc;
> + char *keypath = NULL;
> +
> + rc = cgroup_path_of(group->path, key, &keypath);
> + if (rc < 0)
> + goto out;
> +
> + if (access(keypath, F_OK) != 0)
> + rc = -ENOENT;
> +out:
> + free(keypath);
> +
> + return rc;
> +}
> +
> +static int _cgroup_inherit(virCgroupPtr parent,
> + virCgroupPtr group,
> + const char *key)
> +{
> + int rc;
> + char *keyval = NULL;
> +
> + rc = virCgroupGetValueStr(parent, key, &keyval);
> + if (rc != 0)
> + goto out;
> +
> + rc = virCgroupSetValueStr(group, key, keyval);
> +
> +out:
> + free(keyval);
> +
> + return rc;
> +}
> +
> +static int cgroup_inherit(virCgroupPtr parent,
> + virCgroupPtr group)
> +{
> + int i;
> + int rc = 0;
> + const char *inherit_values[] = {
> + "cpuset.cpus",
> + "cpuset.mems",
> + NULL
> + };
> +
> + for (i = 0; inherit_values[i] != NULL; i++) {
> + const char *key = inherit_values[i];
> + if (virCgroupHasValue(group, key) == 0)
> + rc = _cgroup_inherit(parent, group, key);
> +
> + if (rc != 0) {
> + DEBUG("inherit of %s failed\n", key);
> + break;
> + }
> + }
> +
> + return rc;
> +}
> +
> +static int cgroup_root(virCgroupPtr *root)
> +{
> + int rc = 0;
> + char *grppath = NULL;
> + struct virCgroup _root = { (char *)"." };
> +
> + *root = calloc(1, sizeof(**root));
> + if (*root == NULL) {
> + rc = -ENOMEM;
> + goto out;
> + }
> +
> + (*root)->path = strdup("libvirt");
> + if ((*root)->path == NULL) {
> + rc = -ENOMEM;
> + goto out;
> + }
> +
> + rc = cgroup_path_of(".", (*root)->path, &grppath);
> + if (rc != 0)
> + goto out;
> +
> + if (access(grppath, F_OK) != 0) {
> + if (mkdir(grppath, 0655) != 0)
> + rc = -errno;
> + else
> + rc = cgroup_inherit(&_root, *root);
> + }
Yikes... The whole thing looks messy and magical, what is the code trying to do
with dots and libvirt and 0655's?
> +out:
> + if (rc != 0)
> + virCgroupFree(root);
> + free(grppath);
> +
> + return rc;
> +}
> +
> +static int cgroup_new(virCgroupPtr *parent,
> + const char *group,
> + virCgroupPtr *newgroup)
> +{
> + int rc = 0;
> + char *typpath = NULL;
> +
> + if (*parent == NULL) {
> + rc = cgroup_root(parent);
> + if (rc != 0)
> + goto err;
> + }
> +
> + *newgroup = calloc(1, sizeof(**newgroup));
> + if (*newgroup == NULL) {
> + rc = -ENOMEM;
> + goto err;
> + }
> +
> + rc = asprintf(&((*newgroup)->path),
> + "%s/%s",
> + (*parent)->path,
> + group);
> + if (rc == -1) {
> + rc = -ENOMEM;
> + goto err;
> + }
> +
> + rc = 0;
> +
> + return rc;
> +err:
> + virCgroupFree(newgroup);
> + *newgroup = NULL;
> +
> + free(typpath);
> +
> + return rc;
> +}
> +
> +int virCgroupOpen(virCgroupPtr parent,
> + const char *group,
> + virCgroupPtr *newgroup)
> +{
> + int rc = 0;
> + char *grppath = NULL;
> +
> + rc = cgroup_new(&parent, group, newgroup);
> + if (rc != 0)
> + goto err;
> + virCgroupFree(&parent);
> +
> + rc = cgroup_path_of(".", (*newgroup)->path, &grppath);
> + if (rc != 0)
> + goto err;
> +
> + if (access(grppath, F_OK) != 0) {
> + rc = -ENOENT;
> + goto err;
> + }
> +
> + return rc;
> +err:
> + virCgroupFree(newgroup);
> + *newgroup = NULL;
> +
> + return rc;
> +}
> +
> +int virCgroupCreate(virCgroupPtr parent,
> + const char *group,
> + virCgroupPtr *newgroup)
> +{
> + int rc = 0;
> + char *grppath = NULL;
> + bool free_parent = (parent == NULL);
> +
> + rc = cgroup_new(&parent, group, newgroup);
> + if (rc != 0) {
> + DEBUG0("Unable to allocate new virCgroup structure");
> + goto err;
> + }
> +
> + rc = cgroup_path_of(".", (*newgroup)->path, &grppath);
> + if (rc != 0)
> + goto err;
> +
> + if (access(grppath, F_OK) == 0) {
> + rc = -EEXIST;
> + goto err;
> + }
> +
Why do you need access? mkdir will do that check anyway.
> + if (mkdir(grppath, 0655) != 0) {
Why 0655? Why not use meaningful names see sys/stat.h
> + DEBUG("mkdir of %s failed", grppath);
> + rc = -errno;
> + goto err;
> + }
> +
> + rc = cgroup_inherit(parent, *newgroup);
> + if (rc != 0)
> + goto err;
> +
> + free(grppath);
> +
> + if (free_parent)
> + virCgroupFree(&parent);
> +
> + return rc;
> +err:
> + free(grppath);
> + virCgroupFree(newgroup);
> + *newgroup = NULL;
> +
> + if (free_parent)
> + virCgroupFree(&parent);
> +
> + return rc;
> +}
> +
> +int virCgroupRemove(virCgroupPtr group)
> +{
> + int rc = 0;
> + char *grppath = NULL;
> +
> + rc = cgroup_path_of(".", group->path, &grppath);
> + if (rc != 0)
> + goto out;
> +
> + if (rmdir(grppath) != 0)
> + rc = -errno;
> +out:
> + free(grppath);
> +
> + return rc;
> +}
> +
> +int virCgroupAddTask(virCgroupPtr group, pid_t pid)
> +{
> + int rc = 0;
> + char *pidstr = NULL;
> +
> + if (asprintf(&pidstr, "%lu", (unsigned long)pid) == -1)
> + return -ENOMEM;
> +
> + rc = virCgroupSetValueStr(group, "tasks", pidstr);
> +
> + free(pidstr);
> +
> + return rc;
> +}
> diff -r 444e2614d0a2 -r 8e948eb88328 src/cgroup.h
> --- /dev/null Thu Jan 01 00:00:00 1970 +0000
> +++ b/src/cgroup.h Mon Sep 29 09:37:42 2008 -0700
> @@ -0,0 +1,120 @@
> +/*
> + * cgroup.h: Interface to tools for managing cgroups
> + *
> + * Copyright IBM Corp. 2008
> + *
> + * See COPYING.LIB for the License of this software
> + *
> + * Authors:
> + * Dan Smith <danms@xxxxxxxxxx>
> + */
> +
> +#ifndef CGROUP_H
> +#define CGROUP_H
> +
> +#include <stdint.h>
> +
> +struct virCgroup;
> +typedef struct virCgroup *virCgroupPtr;
> +
> +/**
> + * virCgroupHaveSupport:
> + *
> + * Returns 0 if support is present, negative if not
> + */
> +int virCgroupHaveSupport(void);
> +
> +/**
> + * virCgroupCreate:
> + * @parent: The path to the parent of the desired new group, or NULL if root
> + * @group: The name of the new group
> + * @newgroup: The newly-created group. Must be passed to cgroup_free()
> + *
> + * Returns 0 on success, negative on failure
> + */
> +int virCgroupCreate(virCgroupPtr parent,
> + const char *group,
> + virCgroupPtr *newgroup);
> +
> +/**
> + * virCgroupOpen:
> + * @parent: The path to the parent of the desired new group, or NULL if root
> + * @group: The name of the group
> + * @newgroup: The group. Must be passed to cgroup_free()
> + *
> + * Returns 0 on success, negative on failure
> + */
> +int virCgroupOpen(virCgroupPtr parent,
> + const char *group,
> + virCgroupPtr *newgroup);
> +
> +/**
> + * virCgroupFree:
> + * @group: A pointer to the virCgroupPtr to be freed
> + */
> +void virCgroupFree(virCgroupPtr *group);
> +
> +/**
> + * virCgroupRemove
> + * @parent: The path to the parent of the group to be deleted
> + * @group: The name of the group to be removed
> + *
> + * Returns 0 on success, negative on failure
> + */
> +int virCgroupRemove(virCgroupPtr group);
> +
> +/**
> + * virCgroupHasValue:
> + * @group: The scoping cgroup
> + * @key: The cgrop node to test for
> + *
> + * Returns 0 if present, negative if not
> + */
> +int virCgroupHasValue(virCgroupPtr group, const char *key);
> +
> +/**
> + * virCgroupAddTask:
> + * @group: The scoping cgroup
> + * @pid: The pid of the task to add
> + *
> + * Returns 0 on success, negative on failure
> + */
> +int virCgroupAddTask(virCgroupPtr group, pid_t pid);
> +
> +/**
> + * virCgroupSetValueXXX:
> + * @group: The scoping cgroup
> + * @key: The cgroup node to set
> + * @value: The value to write into the @key node
> + *
> + * Returns 0 on success, negative on failure
> + */
> +int virCgroupSetValueStr(virCgroupPtr group,
> + const char *key,
> + const char *value);
> +int virCgroupSetValueU64(virCgroupPtr group,
> + const char *key,
> + uint64_t value);
> +int virCgroupSetValueI64(virCgroupPtr group,
> + const char *key,
> + int64_t value);
> +
> +/**
> + * virCgroupGetValueXXX:
> + * @group: The scoping cgroup
> + * @key: The cgroup node to read
> + * @value: A pointer to the storage area
> + *
> + * Returns 0 on success, negative on failure
> + */
> +int virCgroupGetValueStr(virCgroupPtr group,
> + const char *key,
> + char **value);
> +int virCgroupGetValueU64(virCgroupPtr group,
> + const char *key,
> + uint64_t *value);
> +int virCgroupGetValueI64(virCgroupPtr group,
> + const char *key,
> + int64_t *value);
> +
> +#endif /* CGROUP_H */
>
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>
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