Currently, dmem charging is driver-driven through direct calls to dmem_cgroup_try_charge(), so cgroup selftests do not have a generic way to trigger charge and uncharge paths from userspace.
This limits any selftest coverage to configuration/readout checks unless a specific driver exposing charge hooks is present in the test environment. Add kernel/cgroup/dmem_selftest.c as a helper module (CONFIG_DMEM_SELFTEST) that registers a synthetic dmem region (dmem_selftest) and exposes debugfs control files: /sys/kernel/debug/dmem_selftest/charge /sys/kernel/debug/dmem_selftest/uncharge Writing a size to charge triggers dmem_cgroup_try_charge() for the calling task's cgroup (the module calls kstrtou64()). Writing to uncharge releases the outstanding charge via dmem_cgroup_uncharge(). Only a single outstanding charge is supported. This provides a deterministic, driver-independent mechanism for exercising dmem accounting paths in selftests. Signed-off-by: Albert Esteve <[email protected]> --- init/Kconfig | 12 +++ kernel/cgroup/Makefile | 1 + kernel/cgroup/dmem_selftest.c | 192 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 205 insertions(+) diff --git a/init/Kconfig b/init/Kconfig index 444ce811ea674..060ba8ca49333 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1238,6 +1238,18 @@ config CGROUP_DMEM As an example, it allows you to restrict VRAM usage for applications in the DRM subsystem. +config DMEM_SELFTEST + tristate "dmem cgroup selftest helper module" + depends on CGROUP_DMEM && DEBUG_FS + default n + help + Builds a small loadable module that registers a dmem region named + "dmem_selftest" and exposes debugfs files under + /sys/kernel/debug/dmem_selftest/ so kselftests can trigger + dmem charge/uncharge operations from userspace. + + Say N unless you run dmem selftests or develop the dmem controller. + config CGROUP_FREEZER bool "Freezer controller" help diff --git a/kernel/cgroup/Makefile b/kernel/cgroup/Makefile index ede31601a363a..febc36e60f9f9 100644 --- a/kernel/cgroup/Makefile +++ b/kernel/cgroup/Makefile @@ -8,4 +8,5 @@ obj-$(CONFIG_CPUSETS) += cpuset.o obj-$(CONFIG_CPUSETS_V1) += cpuset-v1.o obj-$(CONFIG_CGROUP_MISC) += misc.o obj-$(CONFIG_CGROUP_DMEM) += dmem.o +obj-$(CONFIG_DMEM_SELFTEST) += dmem_selftest.o obj-$(CONFIG_CGROUP_DEBUG) += debug.o diff --git a/kernel/cgroup/dmem_selftest.c b/kernel/cgroup/dmem_selftest.c new file mode 100644 index 0000000000000..09df70f718969 --- /dev/null +++ b/kernel/cgroup/dmem_selftest.c @@ -0,0 +1,192 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Kselftest helper for the dmem cgroup controller. + * + * Registers a dmem region and debugfs files so tests can trigger charges + * from the calling task's cgroup. + * + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/cgroup_dmem.h> +#include <linux/debugfs.h> +#include <linux/fs.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/mutex.h> +#include <linux/module.h> +#include <linux/string.h> +#include <linux/uaccess.h> + +#include "../../tools/testing/selftests/kselftest_module.h" + +#define DM_SELFTEST_REGION_NAME "dmem_selftest" +#define DM_SELFTEST_REGION_SIZE (256ULL * 1024 * 1024) + +KSTM_MODULE_GLOBALS(); + +static struct dmem_cgroup_region *selftest_region; +static struct dentry *dbg_dir; + +static struct dmem_cgroup_pool_state *charged_pool; +static u64 charged_size; +static DEFINE_MUTEX(charge_lock); + +static ssize_t dmem_selftest_charge_write(struct file *file, const char __user *user_buf, + size_t count, loff_t *ppos) +{ + struct dmem_cgroup_pool_state *pool = NULL, *limit = NULL; + u64 size; + char buf[32]; + int ret; + + if (!selftest_region) + return -ENODEV; + + if (count == 0 || count >= sizeof(buf)) + return -EINVAL; + + if (copy_from_user(buf, user_buf, count)) + return -EFAULT; + buf[count] = '\0'; + + ret = kstrtou64(strim(buf), 0, &size); + if (ret) + return ret; + if (!size) + return -EINVAL; + + mutex_lock(&charge_lock); + if (charged_pool) { + mutex_unlock(&charge_lock); + return -EBUSY; + } + + ret = dmem_cgroup_try_charge(selftest_region, size, &pool, &limit); + if (ret == -EAGAIN && limit) + dmem_cgroup_pool_state_put(limit); + if (ret) { + mutex_unlock(&charge_lock); + return ret; + } + + charged_pool = pool; + charged_size = size; + mutex_unlock(&charge_lock); + + return count; +} + +static ssize_t dmem_selftest_uncharge_write(struct file *file, const char __user *user_buf, + size_t count, loff_t *ppos) +{ + if (!count) + return -EINVAL; + + mutex_lock(&charge_lock); + if (!charged_pool) { + mutex_unlock(&charge_lock); + return -EINVAL; + } + + dmem_cgroup_uncharge(charged_pool, charged_size); + charged_pool = NULL; + charged_size = 0; + mutex_unlock(&charge_lock); + + return count; +} + +static const struct file_operations dmem_selftest_charge_fops = { + .write = dmem_selftest_charge_write, + .llseek = noop_llseek, +}; + +static const struct file_operations dmem_selftest_uncharge_fops = { + .write = dmem_selftest_uncharge_write, + .llseek = noop_llseek, +}; + +static int __init dmem_selftest_register(void) +{ + selftest_region = dmem_cgroup_register_region( + DM_SELFTEST_REGION_SIZE, DM_SELFTEST_REGION_NAME); + if (IS_ERR(selftest_region)) + return PTR_ERR(selftest_region); + if (!selftest_region) + return -EINVAL; + + dbg_dir = debugfs_create_dir("dmem_selftest", NULL); + if (!dbg_dir) { + dmem_cgroup_unregister_region(selftest_region); + selftest_region = NULL; + return -ENOMEM; + } + + debugfs_create_file("charge", 0200, dbg_dir, NULL, &dmem_selftest_charge_fops); + debugfs_create_file("uncharge", 0200, dbg_dir, NULL, &dmem_selftest_uncharge_fops); + + pr_info("region '%s' registered; debugfs at dmem_selftest/{charge,uncharge}\n", + DM_SELFTEST_REGION_NAME); + return 0; +} + +static void dmem_selftest_remove(void) +{ + debugfs_remove_recursive(dbg_dir); + dbg_dir = NULL; + + if (selftest_region) { + dmem_cgroup_unregister_region(selftest_region); + selftest_region = NULL; + } +} + +static void __init selftest(void) +{ + KSTM_CHECK_ZERO(!selftest_region); + KSTM_CHECK_ZERO(!dbg_dir); +} + +static int __init dmem_selftest_init(void) +{ + int report_rc; + int err; + + err = dmem_selftest_register(); + if (err) + return err; + + pr_info("loaded.\n"); + add_taint(TAINT_TEST, LOCKDEP_STILL_OK); + selftest(); + report_rc = kstm_report(total_tests, failed_tests, skipped_tests); + if (report_rc) { + dmem_selftest_remove(); + return report_rc; + } + + return 0; +} + +static void __exit dmem_selftest_exit(void) +{ + pr_info("unloaded.\n"); + + mutex_lock(&charge_lock); + if (charged_pool) { + dmem_cgroup_uncharge(charged_pool, charged_size); + charged_pool = NULL; + } + mutex_unlock(&charge_lock); + + dmem_selftest_remove(); +} + +module_init(dmem_selftest_init); +module_exit(dmem_selftest_exit); + +MODULE_AUTHOR("Albert Esteve <[email protected]>"); +MODULE_DESCRIPTION("Kselftest helper for cgroup dmem controller"); +MODULE_LICENSE("GPL"); -- 2.52.0
