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-rw-r--r--src/shared/cgroup-setup.c841
1 files changed, 841 insertions, 0 deletions
diff --git a/src/shared/cgroup-setup.c b/src/shared/cgroup-setup.c
new file mode 100644
index 0000000..f197f71
--- /dev/null
+++ b/src/shared/cgroup-setup.c
@@ -0,0 +1,841 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <ftw.h>
+#include <unistd.h>
+
+#include "cgroup-setup.h"
+#include "cgroup-util.h"
+#include "errno-util.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "proc-cmdline.h"
+#include "stdio-util.h"
+#include "string-util.h"
+#include "fs-util.h"
+#include "mkdir.h"
+#include "process-util.h"
+#include "fileio.h"
+#include "user-util.h"
+#include "fd-util.h"
+
+bool cg_is_unified_wanted(void) {
+ static thread_local int wanted = -1;
+ bool b;
+ const bool is_default = DEFAULT_HIERARCHY == CGROUP_UNIFIED_ALL;
+ _cleanup_free_ char *c = NULL;
+ int r;
+
+ /* If we have a cached value, return that. */
+ if (wanted >= 0)
+ return wanted;
+
+ /* If the hierarchy is already mounted, then follow whatever was chosen for it. */
+ r = cg_unified_cached(true);
+ if (r >= 0)
+ return (wanted = r >= CGROUP_UNIFIED_ALL);
+
+ /* If we were explicitly passed systemd.unified_cgroup_hierarchy, respect that. */
+ r = proc_cmdline_get_bool("systemd.unified_cgroup_hierarchy", &b);
+ if (r > 0)
+ return (wanted = b);
+
+ /* If we passed cgroup_no_v1=all with no other instructions, it seems highly unlikely that we want to
+ * use hybrid or legacy hierarchy. */
+ r = proc_cmdline_get_key("cgroup_no_v1", 0, &c);
+ if (r > 0 && streq_ptr(c, "all"))
+ return (wanted = true);
+
+ return (wanted = is_default);
+}
+
+bool cg_is_legacy_wanted(void) {
+ static thread_local int wanted = -1;
+
+ /* If we have a cached value, return that. */
+ if (wanted >= 0)
+ return wanted;
+
+ /* Check if we have cgroup v2 already mounted. */
+ if (cg_unified_cached(true) == CGROUP_UNIFIED_ALL)
+ return (wanted = false);
+
+ /* Otherwise, assume that at least partial legacy is wanted,
+ * since cgroup v2 should already be mounted at this point. */
+ return (wanted = true);
+}
+
+bool cg_is_hybrid_wanted(void) {
+ static thread_local int wanted = -1;
+ int r;
+ bool b;
+ const bool is_default = DEFAULT_HIERARCHY >= CGROUP_UNIFIED_SYSTEMD;
+ /* We default to true if the default is "hybrid", obviously, but also when the default is "unified",
+ * because if we get called, it means that unified hierarchy was not mounted. */
+
+ /* If we have a cached value, return that. */
+ if (wanted >= 0)
+ return wanted;
+
+ /* If the hierarchy is already mounted, then follow whatever was chosen for it. */
+ if (cg_unified_cached(true) == CGROUP_UNIFIED_ALL)
+ return (wanted = false);
+
+ /* Otherwise, let's see what the kernel command line has to say. Since checking is expensive, cache
+ * a non-error result. */
+ r = proc_cmdline_get_bool("systemd.legacy_systemd_cgroup_controller", &b);
+
+ /* The meaning of the kernel option is reversed wrt. to the return value of this function, hence the
+ * negation. */
+ return (wanted = r > 0 ? !b : is_default);
+}
+
+int cg_weight_parse(const char *s, uint64_t *ret) {
+ uint64_t u;
+ int r;
+
+ if (isempty(s)) {
+ *ret = CGROUP_WEIGHT_INVALID;
+ return 0;
+ }
+
+ r = safe_atou64(s, &u);
+ if (r < 0)
+ return r;
+
+ if (u < CGROUP_WEIGHT_MIN || u > CGROUP_WEIGHT_MAX)
+ return -ERANGE;
+
+ *ret = u;
+ return 0;
+}
+
+int cg_cpu_shares_parse(const char *s, uint64_t *ret) {
+ uint64_t u;
+ int r;
+
+ if (isempty(s)) {
+ *ret = CGROUP_CPU_SHARES_INVALID;
+ return 0;
+ }
+
+ r = safe_atou64(s, &u);
+ if (r < 0)
+ return r;
+
+ if (u < CGROUP_CPU_SHARES_MIN || u > CGROUP_CPU_SHARES_MAX)
+ return -ERANGE;
+
+ *ret = u;
+ return 0;
+}
+
+int cg_blkio_weight_parse(const char *s, uint64_t *ret) {
+ uint64_t u;
+ int r;
+
+ if (isempty(s)) {
+ *ret = CGROUP_BLKIO_WEIGHT_INVALID;
+ return 0;
+ }
+
+ r = safe_atou64(s, &u);
+ if (r < 0)
+ return r;
+
+ if (u < CGROUP_BLKIO_WEIGHT_MIN || u > CGROUP_BLKIO_WEIGHT_MAX)
+ return -ERANGE;
+
+ *ret = u;
+ return 0;
+}
+
+static int trim_cb(const char *path, const struct stat *sb, int typeflag, struct FTW *ftwbuf) {
+ assert(path);
+ assert(sb);
+ assert(ftwbuf);
+
+ if (typeflag != FTW_DP)
+ return 0;
+
+ if (ftwbuf->level < 1)
+ return 0;
+
+ (void) rmdir(path);
+ return 0;
+}
+
+int cg_trim(const char *controller, const char *path, bool delete_root) {
+ _cleanup_free_ char *fs = NULL;
+ int r, q;
+
+ assert(path);
+
+ r = cg_get_path(controller, path, NULL, &fs);
+ if (r < 0)
+ return r;
+
+ errno = 0;
+ if (nftw(fs, trim_cb, 64, FTW_DEPTH|FTW_MOUNT|FTW_PHYS) != 0) {
+ if (errno == ENOENT)
+ r = 0;
+ else
+ r = errno_or_else(EIO);
+ }
+
+ if (delete_root) {
+ if (rmdir(fs) < 0 && errno != ENOENT)
+ return -errno;
+ }
+
+ q = cg_hybrid_unified();
+ if (q < 0)
+ return q;
+ if (q > 0 && streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
+ q = cg_trim(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path, delete_root);
+ if (q < 0)
+ log_warning_errno(q, "Failed to trim compat systemd cgroup %s: %m", path);
+ }
+
+ return r;
+}
+
+/* Create a cgroup in the hierarchy of controller.
+ * Returns 0 if the group already existed, 1 on success, negative otherwise.
+ */
+int cg_create(const char *controller, const char *path) {
+ _cleanup_free_ char *fs = NULL;
+ int r;
+
+ r = cg_get_path_and_check(controller, path, NULL, &fs);
+ if (r < 0)
+ return r;
+
+ r = mkdir_parents(fs, 0755);
+ if (r < 0)
+ return r;
+
+ r = mkdir_errno_wrapper(fs, 0755);
+ if (r == -EEXIST)
+ return 0;
+ if (r < 0)
+ return r;
+
+ r = cg_hybrid_unified();
+ if (r < 0)
+ return r;
+
+ if (r > 0 && streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
+ r = cg_create(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path);
+ if (r < 0)
+ log_warning_errno(r, "Failed to create compat systemd cgroup %s: %m", path);
+ }
+
+ return 1;
+}
+
+int cg_create_and_attach(const char *controller, const char *path, pid_t pid) {
+ int r, q;
+
+ assert(pid >= 0);
+
+ r = cg_create(controller, path);
+ if (r < 0)
+ return r;
+
+ q = cg_attach(controller, path, pid);
+ if (q < 0)
+ return q;
+
+ /* This does not remove the cgroup on failure */
+ return r;
+}
+
+int cg_attach(const char *controller, const char *path, pid_t pid) {
+ _cleanup_free_ char *fs = NULL;
+ char c[DECIMAL_STR_MAX(pid_t) + 2];
+ int r;
+
+ assert(path);
+ assert(pid >= 0);
+
+ r = cg_get_path_and_check(controller, path, "cgroup.procs", &fs);
+ if (r < 0)
+ return r;
+
+ if (pid == 0)
+ pid = getpid_cached();
+
+ xsprintf(c, PID_FMT "\n", pid);
+
+ r = write_string_file(fs, c, WRITE_STRING_FILE_DISABLE_BUFFER);
+ if (r < 0)
+ return r;
+
+ r = cg_hybrid_unified();
+ if (r < 0)
+ return r;
+
+ if (r > 0 && streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
+ r = cg_attach(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path, pid);
+ if (r < 0)
+ log_warning_errno(r, "Failed to attach "PID_FMT" to compat systemd cgroup %s: %m", pid, path);
+ }
+
+ return 0;
+}
+
+int cg_attach_fallback(const char *controller, const char *path, pid_t pid) {
+ int r;
+
+ assert(controller);
+ assert(path);
+ assert(pid >= 0);
+
+ r = cg_attach(controller, path, pid);
+ if (r < 0) {
+ char prefix[strlen(path) + 1];
+
+ /* This didn't work? Then let's try all prefixes of
+ * the destination */
+
+ PATH_FOREACH_PREFIX(prefix, path) {
+ int q;
+
+ q = cg_attach(controller, prefix, pid);
+ if (q >= 0)
+ return q;
+ }
+ }
+
+ return r;
+}
+
+int cg_set_access(
+ const char *controller,
+ const char *path,
+ uid_t uid,
+ gid_t gid) {
+
+ struct Attribute {
+ const char *name;
+ bool fatal;
+ };
+
+ /* cgroup v1, aka legacy/non-unified */
+ static const struct Attribute legacy_attributes[] = {
+ { "cgroup.procs", true },
+ { "tasks", false },
+ { "cgroup.clone_children", false },
+ {},
+ };
+
+ /* cgroup v2, aka unified */
+ static const struct Attribute unified_attributes[] = {
+ { "cgroup.procs", true },
+ { "cgroup.subtree_control", true },
+ { "cgroup.threads", false },
+ {},
+ };
+
+ static const struct Attribute* const attributes[] = {
+ [false] = legacy_attributes,
+ [true] = unified_attributes,
+ };
+
+ _cleanup_free_ char *fs = NULL;
+ const struct Attribute *i;
+ int r, unified;
+
+ assert(path);
+
+ if (uid == UID_INVALID && gid == GID_INVALID)
+ return 0;
+
+ unified = cg_unified_controller(controller);
+ if (unified < 0)
+ return unified;
+
+ /* Configure access to the cgroup itself */
+ r = cg_get_path(controller, path, NULL, &fs);
+ if (r < 0)
+ return r;
+
+ r = chmod_and_chown(fs, 0755, uid, gid);
+ if (r < 0)
+ return r;
+
+ /* Configure access to the cgroup's attributes */
+ for (i = attributes[unified]; i->name; i++) {
+ fs = mfree(fs);
+
+ r = cg_get_path(controller, path, i->name, &fs);
+ if (r < 0)
+ return r;
+
+ r = chmod_and_chown(fs, 0644, uid, gid);
+ if (r < 0) {
+ if (i->fatal)
+ return r;
+
+ log_debug_errno(r, "Failed to set access on cgroup %s, ignoring: %m", fs);
+ }
+ }
+
+ if (streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
+ r = cg_hybrid_unified();
+ if (r < 0)
+ return r;
+ if (r > 0) {
+ /* Always propagate access mode from unified to legacy controller */
+ r = cg_set_access(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path, uid, gid);
+ if (r < 0)
+ log_debug_errno(r, "Failed to set access on compatibility systemd cgroup %s, ignoring: %m", path);
+ }
+ }
+
+ return 0;
+}
+
+int cg_migrate(
+ const char *cfrom,
+ const char *pfrom,
+ const char *cto,
+ const char *pto,
+ CGroupFlags flags) {
+
+ bool done = false;
+ _cleanup_set_free_ Set *s = NULL;
+ int r, ret = 0;
+ pid_t my_pid;
+
+ assert(cfrom);
+ assert(pfrom);
+ assert(cto);
+ assert(pto);
+
+ s = set_new(NULL);
+ if (!s)
+ return -ENOMEM;
+
+ my_pid = getpid_cached();
+
+ do {
+ _cleanup_fclose_ FILE *f = NULL;
+ pid_t pid = 0;
+ done = true;
+
+ r = cg_enumerate_processes(cfrom, pfrom, &f);
+ if (r < 0) {
+ if (ret >= 0 && r != -ENOENT)
+ return r;
+
+ return ret;
+ }
+
+ while ((r = cg_read_pid(f, &pid)) > 0) {
+
+ /* This might do weird stuff if we aren't a
+ * single-threaded program. However, we
+ * luckily know we are not */
+ if ((flags & CGROUP_IGNORE_SELF) && pid == my_pid)
+ continue;
+
+ if (set_get(s, PID_TO_PTR(pid)) == PID_TO_PTR(pid))
+ continue;
+
+ /* Ignore kernel threads. Since they can only
+ * exist in the root cgroup, we only check for
+ * them there. */
+ if (cfrom &&
+ empty_or_root(pfrom) &&
+ is_kernel_thread(pid) > 0)
+ continue;
+
+ r = cg_attach(cto, pto, pid);
+ if (r < 0) {
+ if (ret >= 0 && r != -ESRCH)
+ ret = r;
+ } else if (ret == 0)
+ ret = 1;
+
+ done = false;
+
+ r = set_put(s, PID_TO_PTR(pid));
+ if (r < 0) {
+ if (ret >= 0)
+ return r;
+
+ return ret;
+ }
+ }
+
+ if (r < 0) {
+ if (ret >= 0)
+ return r;
+
+ return ret;
+ }
+ } while (!done);
+
+ return ret;
+}
+
+int cg_migrate_recursive(
+ const char *cfrom,
+ const char *pfrom,
+ const char *cto,
+ const char *pto,
+ CGroupFlags flags) {
+
+ _cleanup_closedir_ DIR *d = NULL;
+ int r, ret = 0;
+ char *fn;
+
+ assert(cfrom);
+ assert(pfrom);
+ assert(cto);
+ assert(pto);
+
+ ret = cg_migrate(cfrom, pfrom, cto, pto, flags);
+
+ r = cg_enumerate_subgroups(cfrom, pfrom, &d);
+ if (r < 0) {
+ if (ret >= 0 && r != -ENOENT)
+ return r;
+
+ return ret;
+ }
+
+ while ((r = cg_read_subgroup(d, &fn)) > 0) {
+ _cleanup_free_ char *p = NULL;
+
+ p = path_join(empty_to_root(pfrom), fn);
+ free(fn);
+ if (!p)
+ return -ENOMEM;
+
+ r = cg_migrate_recursive(cfrom, p, cto, pto, flags);
+ if (r != 0 && ret >= 0)
+ ret = r;
+ }
+
+ if (r < 0 && ret >= 0)
+ ret = r;
+
+ if (flags & CGROUP_REMOVE) {
+ r = cg_rmdir(cfrom, pfrom);
+ if (r < 0 && ret >= 0 && !IN_SET(r, -ENOENT, -EBUSY))
+ return r;
+ }
+
+ return ret;
+}
+
+int cg_migrate_recursive_fallback(
+ const char *cfrom,
+ const char *pfrom,
+ const char *cto,
+ const char *pto,
+ CGroupFlags flags) {
+
+ int r;
+
+ assert(cfrom);
+ assert(pfrom);
+ assert(cto);
+ assert(pto);
+
+ r = cg_migrate_recursive(cfrom, pfrom, cto, pto, flags);
+ if (r < 0) {
+ char prefix[strlen(pto) + 1];
+
+ /* This didn't work? Then let's try all prefixes of the destination */
+
+ PATH_FOREACH_PREFIX(prefix, pto) {
+ int q;
+
+ q = cg_migrate_recursive(cfrom, pfrom, cto, prefix, flags);
+ if (q >= 0)
+ return q;
+ }
+ }
+
+ return r;
+}
+
+int cg_create_everywhere(CGroupMask supported, CGroupMask mask, const char *path) {
+ CGroupController c;
+ CGroupMask done;
+ bool created;
+ int r;
+
+ /* This one will create a cgroup in our private tree, but also
+ * duplicate it in the trees specified in mask, and remove it
+ * in all others.
+ *
+ * Returns 0 if the group already existed in the systemd hierarchy,
+ * 1 on success, negative otherwise.
+ */
+
+ /* First create the cgroup in our own hierarchy. */
+ r = cg_create(SYSTEMD_CGROUP_CONTROLLER, path);
+ if (r < 0)
+ return r;
+ created = r;
+
+ /* If we are in the unified hierarchy, we are done now */
+ r = cg_all_unified();
+ if (r < 0)
+ return r;
+ if (r > 0)
+ return created;
+
+ supported &= CGROUP_MASK_V1;
+ mask = CGROUP_MASK_EXTEND_JOINED(mask);
+ done = 0;
+
+ /* Otherwise, do the same in the other hierarchies */
+ for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
+ CGroupMask bit = CGROUP_CONTROLLER_TO_MASK(c);
+ const char *n;
+
+ if (!FLAGS_SET(supported, bit))
+ continue;
+
+ if (FLAGS_SET(done, bit))
+ continue;
+
+ n = cgroup_controller_to_string(c);
+ if (FLAGS_SET(mask, bit))
+ (void) cg_create(n, path);
+
+ done |= CGROUP_MASK_EXTEND_JOINED(bit);
+ }
+
+ return created;
+}
+
+int cg_attach_everywhere(CGroupMask supported, const char *path, pid_t pid, cg_migrate_callback_t path_callback, void *userdata) {
+ int r;
+
+ r = cg_attach(SYSTEMD_CGROUP_CONTROLLER, path, pid);
+ if (r < 0)
+ return r;
+
+ r = cg_all_unified();
+ if (r < 0)
+ return r;
+ if (r > 0)
+ return 0;
+
+ supported &= CGROUP_MASK_V1;
+ CGroupMask done = 0;
+
+ for (CGroupController c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
+ CGroupMask bit = CGROUP_CONTROLLER_TO_MASK(c);
+ const char *p = NULL;
+
+ if (!FLAGS_SET(supported, bit))
+ continue;
+
+ if (FLAGS_SET(done, bit))
+ continue;
+
+ if (path_callback)
+ p = path_callback(bit, userdata);
+ if (!p)
+ p = path;
+
+ (void) cg_attach_fallback(cgroup_controller_to_string(c), p, pid);
+ done |= CGROUP_MASK_EXTEND_JOINED(bit);
+ }
+
+ return 0;
+}
+
+int cg_migrate_v1_controllers(CGroupMask supported, CGroupMask mask, const char *from, cg_migrate_callback_t to_callback, void *userdata) {
+ CGroupController c;
+ CGroupMask done;
+ int r = 0, q;
+
+ assert(to_callback);
+
+ supported &= CGROUP_MASK_V1;
+ mask = CGROUP_MASK_EXTEND_JOINED(mask);
+ done = 0;
+
+ for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
+ CGroupMask bit = CGROUP_CONTROLLER_TO_MASK(c);
+ const char *to = NULL;
+
+ if (!FLAGS_SET(supported, bit))
+ continue;
+
+ if (FLAGS_SET(done, bit))
+ continue;
+
+ if (!FLAGS_SET(mask, bit))
+ continue;
+
+ to = to_callback(bit, userdata);
+
+ /* Remember first error and try continuing */
+ q = cg_migrate_recursive_fallback(SYSTEMD_CGROUP_CONTROLLER, from, cgroup_controller_to_string(c), to, 0);
+ r = (r < 0) ? r : q;
+ }
+
+ return r;
+}
+
+int cg_trim_everywhere(CGroupMask supported, const char *path, bool delete_root) {
+ int r, q;
+
+ r = cg_trim(SYSTEMD_CGROUP_CONTROLLER, path, delete_root);
+ if (r < 0)
+ return r;
+
+ q = cg_all_unified();
+ if (q < 0)
+ return q;
+ if (q > 0)
+ return r;
+
+ return cg_trim_v1_controllers(supported, _CGROUP_MASK_ALL, path, delete_root);
+}
+
+int cg_trim_v1_controllers(CGroupMask supported, CGroupMask mask, const char *path, bool delete_root) {
+ CGroupController c;
+ CGroupMask done;
+ int r = 0, q;
+
+ supported &= CGROUP_MASK_V1;
+ mask = CGROUP_MASK_EXTEND_JOINED(mask);
+ done = 0;
+
+ for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
+ CGroupMask bit = CGROUP_CONTROLLER_TO_MASK(c);
+
+ if (!FLAGS_SET(supported, bit))
+ continue;
+
+ if (FLAGS_SET(done, bit))
+ continue;
+
+ if (FLAGS_SET(mask, bit)) {
+ /* Remember first error and try continuing */
+ q = cg_trim(cgroup_controller_to_string(c), path, delete_root);
+ r = (r < 0) ? r : q;
+ }
+ done |= CGROUP_MASK_EXTEND_JOINED(bit);
+ }
+
+ return r;
+}
+
+int cg_enable_everywhere(
+ CGroupMask supported,
+ CGroupMask mask,
+ const char *p,
+ CGroupMask *ret_result_mask) {
+
+ _cleanup_fclose_ FILE *f = NULL;
+ _cleanup_free_ char *fs = NULL;
+ CGroupController c;
+ CGroupMask ret = 0;
+ int r;
+
+ assert(p);
+
+ if (supported == 0) {
+ if (ret_result_mask)
+ *ret_result_mask = 0;
+ return 0;
+ }
+
+ r = cg_all_unified();
+ if (r < 0)
+ return r;
+ if (r == 0) {
+ /* On the legacy hierarchy there's no concept of "enabling" controllers in cgroups defined. Let's claim
+ * complete success right away. (If you wonder why we return the full mask here, rather than zero: the
+ * caller tends to use the returned mask later on to compare if all controllers where properly joined,
+ * and if not requeues realization. This use is the primary purpose of the return value, hence let's
+ * minimize surprises here and reduce triggers for re-realization by always saying we fully
+ * succeeded.) */
+ if (ret_result_mask)
+ *ret_result_mask = mask & supported & CGROUP_MASK_V2; /* If you wonder why we mask this with
+ * CGROUP_MASK_V2: The 'supported' mask
+ * might contain pure-V1 or BPF
+ * controllers, and we never want to
+ * claim that we could enable those with
+ * cgroup.subtree_control */
+ return 0;
+ }
+
+ r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, p, "cgroup.subtree_control", &fs);
+ if (r < 0)
+ return r;
+
+ for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
+ CGroupMask bit = CGROUP_CONTROLLER_TO_MASK(c);
+ const char *n;
+
+ if (!FLAGS_SET(CGROUP_MASK_V2, bit))
+ continue;
+
+ if (!FLAGS_SET(supported, bit))
+ continue;
+
+ n = cgroup_controller_to_string(c);
+ {
+ char s[1 + strlen(n) + 1];
+
+ s[0] = FLAGS_SET(mask, bit) ? '+' : '-';
+ strcpy(s + 1, n);
+
+ if (!f) {
+ f = fopen(fs, "we");
+ if (!f)
+ return log_debug_errno(errno, "Failed to open cgroup.subtree_control file of %s: %m", p);
+ }
+
+ r = write_string_stream(f, s, WRITE_STRING_FILE_DISABLE_BUFFER);
+ if (r < 0) {
+ log_debug_errno(r, "Failed to %s controller %s for %s (%s): %m",
+ FLAGS_SET(mask, bit) ? "enable" : "disable", n, p, fs);
+ clearerr(f);
+
+ /* If we can't turn off a controller, leave it on in the reported resulting mask. This
+ * happens for example when we attempt to turn off a controller up in the tree that is
+ * used down in the tree. */
+ if (!FLAGS_SET(mask, bit) && r == -EBUSY) /* You might wonder why we check for EBUSY
+ * only here, and not follow the same logic
+ * for other errors such as EINVAL or
+ * EOPNOTSUPP or anything else. That's
+ * because EBUSY indicates that the
+ * controllers is currently enabled and
+ * cannot be disabled because something down
+ * the hierarchy is still using it. Any other
+ * error most likely means something like "I
+ * never heard of this controller" or
+ * similar. In the former case it's hence
+ * safe to assume the controller is still on
+ * after the failed operation, while in the
+ * latter case it's safer to assume the
+ * controller is unknown and hence certainly
+ * not enabled. */
+ ret |= bit;
+ } else {
+ /* Otherwise, if we managed to turn on a controller, set the bit reflecting that. */
+ if (FLAGS_SET(mask, bit))
+ ret |= bit;
+ }
+ }
+ }
+
+ /* Let's return the precise set of controllers now enabled for the cgroup. */
+ if (ret_result_mask)
+ *ret_result_mask = ret;
+
+ return 0;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-29 16:09:06 +0000