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cgroup-util: add helpers for opening cgroup by id

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This commit is contained in:
Lennart Poettering
2023-12-12 10:44:57 +01:00
parent cb1b813f0d
commit 3b2874952f
5 changed files with 109 additions and 13 deletions
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49
src/basic/cgroup-util.c
View File

@@ -22,6 +22,7 @@
#include "log.h"
#include "login-util.h"
#include "macro.h"
#include "missing_fs.h"
#include "missing_magic.h"
#include "missing_threads.h"
#include "mkdir.h"
@@ -39,6 +40,38 @@
#include "user-util.h"
#include "xattr-util.h"
int cg_path_open(const char *controller, const char *path) {
_cleanup_free_ char *fs = NULL;
int r;
r = cg_get_path(controller, path, /* item=*/ NULL, &fs);
if (r < 0)
return r;
return RET_NERRNO(open(fs, O_DIRECTORY|O_CLOEXEC));
}
int cg_cgroupid_open(int cgroupfs_fd, uint64_t id) {
_cleanup_close_ int fsfd = -EBADF;
if (cgroupfs_fd < 0) {
fsfd = open("/sys/fs/cgroup", O_CLOEXEC|O_DIRECTORY);
if (fsfd < 0)
return -errno;
cgroupfs_fd = fsfd;
}
cg_file_handle fh = CG_FILE_HANDLE_INIT;
CG_FILE_HANDLE_CGROUPID(fh) = id;
int fd = open_by_handle_at(cgroupfs_fd, &fh.file_handle, O_DIRECTORY|O_CLOEXEC);
if (fd < 0)
return -errno;
return fd;
}
static int cg_enumerate_items(const char *controller, const char *path, FILE **ret, const char *item) {
_cleanup_free_ char *fs = NULL;
FILE *f;
@@ -1404,7 +1437,7 @@ int cg_pid_get_machine_name(pid_t pid, char **ret_machine) {
int cg_path_get_cgroupid(const char *path, uint64_t *ret) {
cg_file_handle fh = CG_FILE_HANDLE_INIT;
int mnt_id = -1;
int mnt_id;
assert(path);
assert(ret);
@@ -1418,6 +1451,20 @@ int cg_path_get_cgroupid(const char *path, uint64_t *ret) {
return 0;
}
int cg_fd_get_cgroupid(int fd, uint64_t *ret) {
cg_file_handle fh = CG_FILE_HANDLE_INIT;
int mnt_id = -1;
assert(fd >= 0);
assert(ret);
if (name_to_handle_at(fd, "", &fh.file_handle, &mnt_id, AT_EMPTY_PATH) < 0)
return -errno;
*ret = CG_FILE_HANDLE_CGROUPID(fh);
return 0;
}
int cg_path_get_session(const char *path, char **ret_session) {
_cleanup_free_ char *unit = NULL;
char *start, *end;

11
src/basic/cgroup-util.h
View File

@@ -180,6 +180,9 @@ typedef enum CGroupUnified {
* generate paths with multiple adjacent / removed.
*/
int cg_path_open(const char *controller, const char *path);
int cg_cgroupid_open(int fsfd, uint64_t id);
int cg_enumerate_processes(const char *controller, const char *path, FILE **ret);
int cg_read_pid(FILE *f, pid_t *ret);
int cg_read_pidref(FILE *f, PidRef *ret);
@@ -267,6 +270,7 @@ int cg_is_empty_recursive(const char *controller, const char *path);
int cg_get_root_path(char **path);
int cg_path_get_cgroupid(const char *path, uint64_t *ret);
int cg_fd_get_cgroupid(int fd, uint64_t *ret);
int cg_path_get_session(const char *path, char **ret_session);
int cg_path_get_owner_uid(const char *path, uid_t *ret_uid);
int cg_path_get_unit(const char *path, char **ret_unit);
@@ -352,5 +356,10 @@ typedef union {
uint8_t space[offsetof(struct file_handle, f_handle) + sizeof(uint64_t)];
} cg_file_handle;
#define CG_FILE_HANDLE_INIT { .file_handle.handle_bytes = sizeof(uint64_t) }
#define CG_FILE_HANDLE_INIT \
(cg_file_handle) { \
.file_handle.handle_bytes = sizeof(uint64_t), \
.file_handle.handle_type = FILEID_KERNFS, \
}
#define CG_FILE_HANDLE_CGROUPID(fh) (*(uint64_t*) (fh).file_handle.f_handle)

5
src/basic/missing_fs.h
View File

@@ -111,3 +111,8 @@ assert_cc(FS_PROJINHERIT_FL == 0x20000000);
#else
assert_cc(FS_KEY_DESCRIPTOR_SIZE == 8);
#endif
/* linux/exportfs.h */
#ifndef FILEID_KERNFS
#define FILEID_KERNFS 0xfe
#endif

13
src/shared/cgroup-show.c
View File

@@ -150,18 +150,9 @@ static int show_cgroup_name(
delegate = r > 0;
if (FLAGS_SET(flags, OUTPUT_CGROUP_ID)) {
cg_file_handle fh = CG_FILE_HANDLE_INIT;
int mnt_id = -1;
if (name_to_handle_at(
fd,
"",
&fh.file_handle,
&mnt_id,
AT_EMPTY_PATH) < 0)
r = cg_fd_get_cgroupid(fd, &cgroupid);
if (r < 0)
log_debug_errno(errno, "Failed to determine cgroup ID of %s, ignoring: %m", path);
else
cgroupid = CG_FILE_HANDLE_CGROUPID(fh);
}
r = path_extract_filename(path, &b);

44
src/test/test-cgroup.c
View File

@@ -5,6 +5,7 @@
#include "cgroup-setup.h"
#include "cgroup-util.h"
#include "errno-util.h"
#include "fd-util.h"
#include "path-util.h"
#include "process-util.h"
#include "string-util.h"
@@ -129,4 +130,47 @@ TEST(cg_create) {
assert_se(cg_rmdir(SYSTEMD_CGROUP_CONTROLLER, test_a) == 0);
}
TEST(id) {
_cleanup_free_ char *p = NULL, *p2 = NULL;
_cleanup_close_ int fd = -EBADF, fd2 = -EBADF;
uint64_t id, id2;
int r;
r = cg_all_unified();
if (r == 0) {
log_tests_skipped("skipping cgroupid test, not running in unified mode");
return;
}
if (IN_SET(r, -ENOMEDIUM, -ENOENT)) {
log_tests_skipped("cgroupfs is not mounted");
return;
}
assert_se(r > 0);
fd = cg_path_open(SYSTEMD_CGROUP_CONTROLLER, "/");
assert_se(fd >= 0);
assert_se(fd_get_path(fd, &p) >= 0);
assert_se(path_equal(p, "/sys/fs/cgroup"));
assert_se(cg_fd_get_cgroupid(fd, &id) >= 0);
fd2 = cg_cgroupid_open(fd, id);
if (ERRNO_IS_NEG_PRIVILEGE(fd2))
log_notice("Skipping open-by-cgroup-id test because lacking privs.");
else {
assert_se(fd2 >= 0);
assert_se(fd_get_path(fd2, &p2) >= 0);
assert_se(path_equal(p2, "/sys/fs/cgroup"));
assert_se(cg_fd_get_cgroupid(fd2, &id2) >= 0);
assert_se(id == id2);
assert_se(inode_same_at(fd, NULL, fd2, NULL, AT_EMPTY_PATH) > 0);
}
}
DEFINE_TEST_MAIN(LOG_DEBUG);