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[libvirt] [PATCH 1 of 2] Add internal cgroup manipulation functions



This patch adds src/cgroup.{c,h} with support for creating and manipulating
cgroups.

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 creates groups in all mounts requires to get memory and devices
functionality.  When setting a value, the appropriate mount is determined
and the value is set there.  I have tested this with all controllers mounted
in a single location, as well as all of them mounted separately.

Changes:
 - Handle multiple mount points
 - Add more abstract internal API, per recent discussion
 - Consider absence of memory or devices controllers as "no cgroup support"

diff -r 444e2614d0a2 -r c33c6d6369e4 src/cgroup.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/cgroup.c	Wed Oct 01 13:16:03 2008 -0700
@@ -0,0 +1,705 @@
+/*
+ * cgroup.c: Tools for managing cgroups
+ *
+ * Copyright IBM Corp. 2008
+ *
+ * See COPYING.LIB for the License of this software
+ *
+ * Authors:
+ *  Dan Smith <danms us ibm com>
+ */
+#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 "memory.h"
+#include "cgroup.h"
+
+#define DEBUG(fmt,...) VIR_DEBUG(__FILE__, fmt, __VA_ARGS__)
+#define DEBUG0(msg) VIR_DEBUG(__FILE__, "%s", msg)
+
+#define CGROUP_MAX_VAL 512
+
+struct virCgroup {
+    char *path;
+};
+
+const char *supported_controllers[] = {
+    "memory",
+    "devices",
+    NULL
+};
+
+void virCgroupFree(virCgroupPtr *group)
+{
+    if (*group != NULL) {
+        VIR_FREE((*group)->path);
+        VIR_FREE(*group);
+        *group = NULL;
+    }
+}
+
+static virCgroupPtr virCgroupGetMount(const char *controller)
+{
+    FILE *mounts;
+    struct mntent entry;
+    char buf[CGROUP_MAX_VAL];
+    virCgroupPtr root = NULL;
+
+    if (VIR_ALLOC(root) != 0)
+        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") &&
+            (strstr(entry.mnt_opts, controller))) {
+            root->path = strdup(entry.mnt_dir);
+            break;
+        }
+    }
+
+    DEBUG("Mount for %s is %s\n", controller, root->path);
+
+    if (root->path == NULL) {
+        DEBUG0("Did not find cgroup mount");
+        goto err;
+    }
+
+    fclose(mounts);
+
+    return root;
+err:
+    virCgroupFree(&root);
+
+    return NULL;
+}
+
+int virCgroupHaveSupport(void)
+{
+    virCgroupPtr root;
+    int i;
+
+    for (i = 0; supported_controllers[i] != NULL; i++) {
+        root = virCgroupGetMount(supported_controllers[i]);
+        if (root == NULL)
+            return -1;
+        virCgroupFree(&root);
+    }
+
+    return 0;
+}
+
+static int virCgroupPathOfGroup(const char *group,
+                                const char *controller,
+                                char **path)
+{
+    virCgroupPtr root = NULL;
+    int rc = 0;
+
+    root = virCgroupGetMount(controller);
+    if (root == NULL) {
+        rc = -ENOTDIR;
+        goto out;
+    }
+
+    if (asprintf(path, "%s/%s", root->path, group) == -1)
+        rc = -ENOMEM;
+out:
+    virCgroupFree(&root);
+
+    return rc;
+}
+
+static int virCgroupPathOf(const char *grppath,
+                           const char *key,
+                           char **path)
+{
+    virCgroupPtr root;
+    int rc = 0;
+    char *controller = NULL;
+
+    if (strchr(key, '.') == NULL)
+        return -EINVAL;
+
+    if (sscanf(key, "%a[^.]", &controller) != 1)
+        return -EINVAL;
+
+    root = virCgroupGetMount(controller);
+    if (root == NULL) {
+        rc = -ENOTDIR;
+        goto out;
+    }
+
+    if (asprintf(path, "%s/%s/%s", root->path, grppath, key) == -1)
+        rc = -ENOMEM;
+out:
+    virCgroupFree(&root);
+    VIR_FREE(controller);
+
+    return rc;
+}
+
+static int virCgroupSetValueStr(virCgroupPtr group,
+                                const char *key,
+                                const char *value)
+{
+    int fd = -1;
+    int rc = 0;
+    char *keypath = NULL;
+
+    rc = virCgroupPathOf(group->path, key, &keypath);
+    if (rc != 0)
+        return rc;
+
+    fd = open(keypath, O_WRONLY);
+    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:
+    VIR_FREE(keypath);
+    close(fd);
+
+    return rc;
+}
+
+static 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);
+
+    VIR_FREE(strval);
+
+    return rc;
+}
+
+#if 0
+/* This is included for completeness, but not yet used */
+
+static 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);
+
+    VIR_FREE(strval);
+
+    return rc;
+}
+
+static int virCgroupGetValueStr(virCgroupPtr group,
+                                const char *key,
+                                char **value)
+{
+    int fd = -1;
+    int rc;
+    char *keypath = NULL;
+    char buf[CGROUP_MAX_VAL];
+
+    memset(buf, 0, sizeof(buf));
+
+    rc = virCgroupPathOf(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:
+    VIR_FREE(keypath);
+    close(fd);
+
+    return rc;
+}
+
+static 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:
+    VIR_FREE(strval);
+
+    return rc;
+}
+
+static 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:
+    VIR_FREE(strval);
+
+    return rc;
+}
+#endif
+
+static int _virCgroupInherit(const char *path,
+                             const char *key)
+{
+    int rc = 0;
+    int fd = -1;
+    char buf[CGROUP_MAX_VAL];
+    char *keypath = NULL;
+    char *pkeypath = NULL;
+
+    memset(buf, 0, sizeof(buf));
+
+    if (asprintf(&keypath, "%s/%s", path, key) == -1) {
+        rc = -ENOMEM;
+        goto out;
+    }
+
+    if (access(keypath, F_OK) != 0) {
+        DEBUG("Group %s has no key %s\n", path, key);
+        goto out;
+    }
+
+    if (asprintf(&pkeypath, "%s/../%s", path, key) == -1) {
+        rc = -ENOMEM;
+        VIR_FREE(keypath);
+        goto out;
+    }
+
+    fd = open(pkeypath, O_RDONLY);
+    if (fd < 0) {
+        rc = -errno;
+        goto out;
+    }
+
+    if (saferead(fd, buf, sizeof(buf)) <= 0) {
+        rc = -errno;
+        goto out;
+    }
+
+    close(fd);
+
+    fd = open(keypath, O_WRONLY);
+    if (fd < 0) {
+        rc = -errno;
+        goto out;
+    }
+
+    if (safewrite(fd, buf, strlen(buf)) != strlen(buf)) {
+        rc = -errno;
+        goto out;
+    }
+
+out:
+    VIR_FREE(keypath);
+    VIR_FREE(pkeypath);
+    close(fd);
+
+    return rc;
+}
+
+static int virCgroupInherit(const char *grppath)
+{
+    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];
+
+        rc = _virCgroupInherit(grppath, key);
+        if (rc != 0) {
+            DEBUG("inherit of %s failed\n", key);
+            break;
+        }
+    }
+
+    return rc;
+}
+
+static int virCgroupMakeGroup(const char *name)
+{
+    int i;
+    int rc = 0;
+
+    for (i = 0; supported_controllers[i] != NULL; i++) {
+        char *path = NULL;
+        virCgroupPtr root;
+
+        root = virCgroupGetMount(supported_controllers[i]);
+        if (root == NULL)
+            continue;
+
+        rc = virCgroupPathOfGroup(name, supported_controllers[i], &path);
+        if (rc != 0) {
+            virCgroupFree(&root);
+            break;
+        }
+
+        virCgroupFree(&root);
+
+        if (access(path, F_OK) != 0) {
+            if (mkdir(path, 0655) < 0) {
+                rc = -errno;
+                VIR_FREE(path);
+                break;
+            }
+            virCgroupInherit(path);
+        }
+
+        VIR_FREE(path);
+    }
+
+    return rc;
+}
+
+static int virCgroupRoot(virCgroupPtr *root)
+{
+    int rc = 0;
+    char *grppath = NULL;
+
+    if (VIR_ALLOC((*root)) != 0) {
+        rc = -ENOMEM;
+        goto out;
+    }
+
+    (*root)->path = strdup("libvirt");
+    if ((*root)->path == NULL) {
+        rc = -ENOMEM;
+        goto out;
+    }
+
+    rc = virCgroupMakeGroup((*root)->path);
+out:
+    if (rc != 0)
+        virCgroupFree(root);
+    VIR_FREE(grppath);
+
+    return rc;
+}
+
+static int virCgroupNew(virCgroupPtr *parent,
+                        const char *group,
+                        virCgroupPtr *newgroup)
+{
+    int rc = 0;
+    char *typpath = NULL;
+
+    *newgroup = NULL;
+
+    if (*parent == NULL) {
+        rc = virCgroupRoot(parent);
+        if (rc != 0)
+            goto err;
+    }
+
+    if (VIR_ALLOC((*newgroup)) != 0) {
+        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;
+
+    VIR_FREE(typpath);
+
+    return rc;
+}
+
+static int virCgroupOpen(virCgroupPtr parent,
+                         const char *group,
+                         virCgroupPtr *newgroup)
+{
+    int rc = 0;
+    char *grppath = NULL;
+    bool free_parent = (parent == NULL);
+
+    rc = virCgroupNew(&parent, group, newgroup);
+    if (rc != 0)
+        goto err;
+
+    if (free_parent)
+        virCgroupFree(&parent);
+
+    rc = virCgroupPathOfGroup((*newgroup)->path,
+                              supported_controllers[0],
+                              &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;
+}
+
+static int virCgroupCreate(virCgroupPtr parent,
+                           const char *group,
+                           virCgroupPtr *newgroup)
+{
+    int rc = 0;
+    bool free_parent = (parent == NULL);
+
+    rc = virCgroupNew(&parent, group, newgroup);
+    if (rc != 0) {
+        DEBUG0("Unable to allocate new virCgroup structure");
+        goto err;
+    }
+
+    rc = virCgroupMakeGroup((*newgroup)->path);
+    if (rc != 0)
+        goto err;
+
+    if (free_parent)
+        virCgroupFree(&parent);
+
+    return rc;
+err:
+    virCgroupFree(newgroup);
+    *newgroup = NULL;
+
+    if (free_parent)
+        virCgroupFree(&parent);
+
+    return rc;
+}
+
+int virCgroupRemove(virCgroupPtr group)
+{
+    int rc = 0;
+    int i;
+    char *grppath = NULL;
+
+    for (i = 0; supported_controllers[i] != NULL; i++) {
+        if (virCgroupPathOfGroup(group->path,
+                                 supported_controllers[i],
+                                 &grppath) != 0)
+            continue;
+
+        if (rmdir(grppath) != 0)
+            rc = -errno;
+
+        VIR_FREE(grppath);
+    }
+
+    return rc;
+}
+
+int virCgroupAddTask(virCgroupPtr group, pid_t pid)
+{
+    int rc = 0;
+    int fd = -1;
+    int i;
+    char *grppath = NULL;
+    char *taskpath = NULL;
+    char *pidstr = NULL;
+
+    for (i = 0; supported_controllers[i] != NULL; i++) {
+        rc = virCgroupPathOfGroup(group->path,
+                                  supported_controllers[i],
+                                  &grppath);
+        if (rc != 0)
+            goto done;
+
+        if (asprintf(&taskpath, "%s/tasks", grppath) == -1) {
+            rc = -ENOMEM;
+            goto done;
+        }
+
+        fd = open(taskpath, O_WRONLY);
+        if (fd < 0) {
+            rc = -errno;
+            goto done;
+        }
+
+        if (asprintf(&pidstr, "%lu", (unsigned long)pid) == -1) {
+            rc = -ENOMEM;
+            goto done;
+        }
+
+        if (write(fd, pidstr, strlen(pidstr)) <= 0) {
+            rc = -errno;
+            goto done;
+        }
+
+    done:
+        VIR_FREE(grppath);
+        VIR_FREE(taskpath);
+        VIR_FREE(pidstr);
+        close(fd);
+
+        if (rc != 0)
+            break;
+    }
+
+    return rc;
+}
+
+int virCgroupForDomain(virDomainDefPtr def, virCgroupPtr *group)
+{
+    int rc;
+    virCgroupPtr typegrp = NULL;
+    const char *typestr = virDomainVirtTypeToString(def->virtType);
+
+    if (typestr == NULL)
+        return -EINVAL;
+
+    rc = virCgroupOpen(NULL, typestr, &typegrp);
+    if (rc == -ENOENT) {
+        rc = virCgroupCreate(NULL, typestr, &typegrp);
+        if (rc != 0)
+            goto out;
+    } else if (rc != 0)
+        goto out;
+
+    rc = virCgroupOpen(typegrp, def->name, group);
+    if (rc == -ENOENT)
+        rc = virCgroupCreate(typegrp, def->name, group);
+out:
+    virCgroupFree(&typegrp);
+
+    return rc;
+}
+
+int virCgroupSetMemory(virCgroupPtr group, unsigned long kb)
+{
+    return virCgroupSetValueU64(group,
+                                "memory.limit_in_bytes",
+                                kb << 10);
+}
+
+int virCgroupDenyAllDevices(virCgroupPtr group)
+{
+    return virCgroupSetValueStr(group,
+                              "devices.deny",
+                              "a");
+}
+
+int virCgroupAllowDevice(virCgroupPtr group,
+                         char type,
+                         int major,
+                         int minor)
+{
+    int rc;
+    char *devstr = NULL;
+
+    if (asprintf(&devstr, "%c %i:%i rwm", type, major, minor) == -1) {
+        rc = -ENOMEM;
+        goto out;
+    }
+
+    rc = virCgroupSetValueStr(group,
+                              "devices.allow",
+                              devstr);
+out:
+    VIR_FREE(devstr);
+
+    return rc;
+}
diff -r 444e2614d0a2 -r c33c6d6369e4 src/cgroup.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/cgroup.h	Wed Oct 01 13:16:03 2008 -0700
@@ -0,0 +1,99 @@
+/*
+ * 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 us ibm com>
+ */
+
+#ifndef CGROUP_H
+#define CGROUP_H
+
+#include <stdint.h>
+
+struct virCgroup;
+typedef struct virCgroup *virCgroupPtr;
+
+#include "domain_conf.h"
+
+/**
+ * virCgroupHaveSupport:
+ *
+ * Returns 0 if support is present, negative if not
+ */
+int virCgroupHaveSupport(void);
+
+/**
+ * virCgroupForDomain:
+ *
+ * @def: Domain definition to create cgroup for
+ * @group: Pointer to returned virCgroupPtr
+ *
+ * Returns 0 on success
+ */
+int virCgroupForDomain(virDomainDefPtr def, virCgroupPtr *group);
+
+/**
+ * virCgroupAddTask:
+ *
+ * @group: The cgroup to add a task to
+ * @pid: The pid of the task to add
+ *
+ * Returns: 0 on success
+ */
+int virCgroupAddTask(virCgroupPtr group, pid_t pid);
+
+/**
+ * virCgroupSetMemory:
+ *
+ * @group: The cgroup to change memory for
+ * @kb: The memory amount in kilobytes
+ *
+ * Returns: 0 on success
+ */
+int virCgroupSetMemory(virCgroupPtr group, unsigned long kb);
+
+/**
+ * virCgroupDenyAllDevices:
+ *
+ * @group: The cgroup to deny devices for
+ *
+ * Returns: 0 on success
+ */
+int virCgroupDenyAllDevices(virCgroupPtr group);
+
+/**
+ * virCgroupAllowDevice:
+ *
+ * @group: The cgroup to allow a device for
+ * @type: The device type (i.e., 'c' or 'b')
+ * @major: The major number of the device
+ * @minor: The minor number of the device
+ *
+ * Returns: 0 on success
+ */
+int virCgroupAllowDevice(virCgroupPtr group,
+                         char type,
+                         int major,
+                         int minor);
+
+/**
+ * virCgroupRemove:
+ *
+ * @group: The group to be removed
+ *
+ * Returns: 0 on success
+ */
+int virCgroupRemove(virCgroupPtr group);
+
+/**
+ * virCgroupFree:
+ *
+ * @group: The group structure to free
+ */
+void virCgroupFree(virCgroupPtr *group);
+
+#endif /* CGROUP_H */


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