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![Sargun Dhillon](/assets/img/avatar_default.png)
This patch modifies test_current_task_under_cgroup_user. The test has several helpers around creating a temporary environment for cgroup testing, and moving the current task around cgroups. This set of helpers can then be used in other tests. Signed-off-by: Sargun Dhillon <sargun@sargun.me> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
177 lines
4.4 KiB
C
177 lines
4.4 KiB
C
#define _GNU_SOURCE
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#include <sched.h>
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#include <sys/mount.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <linux/limits.h>
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#include <stdio.h>
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#include <linux/sched.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <ftw.h>
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#include "cgroup_helpers.h"
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/*
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* To avoid relying on the system setup, when setup_cgroup_env is called
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* we create a new mount namespace, and cgroup namespace. The cgroup2
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* root is mounted at CGROUP_MOUNT_PATH
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*
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* Unfortunately, most people don't have cgroupv2 enabled at this point in time.
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* It's easier to create our own mount namespace and manage it ourselves.
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*
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* We assume /mnt exists.
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*/
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#define WALK_FD_LIMIT 16
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#define CGROUP_MOUNT_PATH "/mnt"
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#define CGROUP_WORK_DIR "/cgroup-test-work-dir"
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#define format_cgroup_path(buf, path) \
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snprintf(buf, sizeof(buf), "%s%s%s", CGROUP_MOUNT_PATH, \
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CGROUP_WORK_DIR, path)
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/**
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* setup_cgroup_environment() - Setup the cgroup environment
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*
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* After calling this function, cleanup_cgroup_environment should be called
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* once testing is complete.
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*
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* This function will print an error to stderr and return 1 if it is unable
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* to setup the cgroup environment. If setup is successful, 0 is returned.
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*/
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int setup_cgroup_environment(void)
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{
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char cgroup_workdir[PATH_MAX + 1];
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format_cgroup_path(cgroup_workdir, "");
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if (unshare(CLONE_NEWNS)) {
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log_err("unshare");
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return 1;
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}
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if (mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL)) {
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log_err("mount fakeroot");
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return 1;
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}
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if (mount("none", CGROUP_MOUNT_PATH, "cgroup2", 0, NULL)) {
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log_err("mount cgroup2");
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return 1;
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}
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/* Cleanup existing failed runs, now that the environment is setup */
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cleanup_cgroup_environment();
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if (mkdir(cgroup_workdir, 0777) && errno != EEXIST) {
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log_err("mkdir cgroup work dir");
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return 1;
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}
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return 0;
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}
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static int nftwfunc(const char *filename, const struct stat *statptr,
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int fileflags, struct FTW *pfwt)
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{
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if ((fileflags & FTW_D) && rmdir(filename))
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log_err("Removing cgroup: %s", filename);
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return 0;
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}
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static int join_cgroup_from_top(char *cgroup_path)
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{
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char cgroup_procs_path[PATH_MAX + 1];
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pid_t pid = getpid();
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int fd, rc = 0;
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snprintf(cgroup_procs_path, sizeof(cgroup_procs_path),
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"%s/cgroup.procs", cgroup_path);
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fd = open(cgroup_procs_path, O_WRONLY);
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if (fd < 0) {
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log_err("Opening Cgroup Procs: %s", cgroup_procs_path);
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return 1;
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}
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if (dprintf(fd, "%d\n", pid) < 0) {
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log_err("Joining Cgroup");
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rc = 1;
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}
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close(fd);
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return rc;
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}
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/**
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* join_cgroup() - Join a cgroup
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* @path: The cgroup path, relative to the workdir, to join
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*
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* This function expects a cgroup to already be created, relative to the cgroup
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* work dir, and it joins it. For example, passing "/my-cgroup" as the path
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* would actually put the calling process into the cgroup
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* "/cgroup-test-work-dir/my-cgroup"
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*
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* On success, it returns 0, otherwise on failure it returns 1.
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*/
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int join_cgroup(char *path)
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{
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char cgroup_path[PATH_MAX + 1];
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format_cgroup_path(cgroup_path, path);
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return join_cgroup_from_top(cgroup_path);
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}
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/**
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* cleanup_cgroup_environment() - Cleanup Cgroup Testing Environment
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*
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* This is an idempotent function to delete all temporary cgroups that
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* have been created during the test, including the cgroup testing work
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* directory.
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*
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* At call time, it moves the calling process to the root cgroup, and then
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* runs the deletion process. It is idempotent, and should not fail, unless
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* a process is lingering.
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*
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* On failure, it will print an error to stderr, and try to continue.
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*/
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void cleanup_cgroup_environment(void)
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{
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char cgroup_workdir[PATH_MAX + 1];
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format_cgroup_path(cgroup_workdir, "");
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join_cgroup_from_top(CGROUP_MOUNT_PATH);
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nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH | FTW_MOUNT);
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}
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/**
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* create_and_get_cgroup() - Create a cgroup, relative to workdir, and get the FD
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* @path: The cgroup path, relative to the workdir, to join
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*
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* This function creates a cgroup under the top level workdir and returns the
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* file descriptor. It is idempotent.
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*
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* On success, it returns the file descriptor. On failure it returns 0.
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* If there is a failure, it prints the error to stderr.
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*/
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int create_and_get_cgroup(char *path)
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{
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char cgroup_path[PATH_MAX + 1];
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int fd;
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format_cgroup_path(cgroup_path, path);
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if (mkdir(cgroup_path, 0777) && errno != EEXIST) {
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log_err("mkdiring cgroup");
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return 0;
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}
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fd = open(cgroup_path, O_RDONLY);
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if (fd < 0) {
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log_err("Opening Cgroup");
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return 0;
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}
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return fd;
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}
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