[Devel] [PATCH VZ10 v5 9/9] selftests/ve: Add mount accounting selftest
Vasileios Almpanis
vasileios.almpanis at virtuozzo.com
Fri Aug 7 13:01:18 MSK 2026
On 8/2/26 1:40 PM, Vladimir Riabchun wrote:
> There are 6 test cases, covered in the new test:
> 1. Simple mount accouting correctness, just mount/umount.
> 2. Verification of correct limit hits and changes, including
> negative values.
> 3. Patial mounts test, when mount limit is hit in the middle
> of creation.
nit: Partial
> 4. Test that enabled pseudosuper allows overuse.
> 5. Test that pseudosuper doesn't affect mount accoutning.
nit: accounting
> 6. Failcount feature verification.
>
> https://virtuozzo.atlassian.net/browse/VSTOR-135520
>
> Feature: per-ve failcounters
> Signed-off-by: Vladimir Riabchun <vladimir.riabchun at virtuozzo.com>
> ---
> v4 -> v5:
> - Splitted pseudosuper test into two.
> - Added new test to check that things go smoothly when
> we run out of mounts in the middle of a new mount.
>
> tools/testing/selftests/ve/.gitignore | 1 +
> tools/testing/selftests/ve/Makefile | 1 +
> .../selftests/ve/ve_mount_accounting_test.c | 419 ++++++++++++++++++
> 3 files changed, 421 insertions(+)
> create mode 100644 tools/testing/selftests/ve/ve_mount_accounting_test.c
>
> diff --git a/tools/testing/selftests/ve/.gitignore b/tools/testing/selftests/ve/.gitignore
> index afa4c568c2c9..3df4d05888dc 100644
> --- a/tools/testing/selftests/ve/.gitignore
> +++ b/tools/testing/selftests/ve/.gitignore
> @@ -1,2 +1,3 @@
> ve_ns_owner_test
> ve_perms_test
> +ve_mount_accounting_test
> diff --git a/tools/testing/selftests/ve/Makefile b/tools/testing/selftests/ve/Makefile
> index ec40cbc7b3a1..c6efe7c4b4fb 100644
> --- a/tools/testing/selftests/ve/Makefile
> +++ b/tools/testing/selftests/ve/Makefile
> @@ -4,5 +4,6 @@ CFLAGS += -g -Wall -O2
>
> TEST_GEN_PROGS += ve_ns_owner_test
> TEST_GEN_PROGS += ve_perms_test
> +TEST_GEN_PROGS += ve_mount_accounting_test
>
> include ../lib.mk
> diff --git a/tools/testing/selftests/ve/ve_mount_accounting_test.c b/tools/testing/selftests/ve/ve_mount_accounting_test.c
> new file mode 100644
> index 000000000000..b295290ec6e8
> --- /dev/null
> +++ b/tools/testing/selftests/ve/ve_mount_accounting_test.c
> @@ -0,0 +1,419 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * ve_mount_accounting selftests
> + *
> + * Tests to check the correctness of mount accounting.
> + */
> +#define _GNU_SOURCE
> +#include <linux/sched.h>
> +#include <linux/mount.h>
Is linux/mount needed here? You include both linux/mount and sys/mount.
You only call mount,umount so dropping it looks generally safe.
> +#include <sched.h>
> +#include <sys/wait.h>
> +#include <sys/syscall.h>
> +#include <unistd.h>
> +#include <asm/unistd.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <fcntl.h>
> +#include <string.h>
> +#include <sys/stat.h>
> +#include <sys/mount.h>
> +#include <linux/limits.h>
> +#include <errno.h>
> +
> +#include "../kselftest_harness.h"
> +#include "ve_selftest.h"
> +
> +#define TMP_DIR "/ve-mnt-tmp/"
> +#define VE_MOUNTS_MAX 128
> +
> +static int set_pseudosuper(int cgv2_fd, int ctid, int value)
> +{
> + char path[64];
> +
> + snprintf(path, sizeof(path), "%d/ve.pseudosuper", ctid);
> + return write_u64_at(cgv2_fd, path, value);
> +}
> +
> +static int _create_mount(void *id_ptr)
> +{
> + char path[PATH_MAX];
> + int id = *(int *)id_ptr, ret;
> +
> + snprintf(path, sizeof(path), TMP_DIR "%d", id);
> +
> + if (mkdir(path, 0755) < 0) {
> + fprintf(stderr, "Failed to create directory %s: %s\n", path, strerror(errno));
> + return -1;
> + }
> + ret = mount("tmpfs", path, "tmpfs", 0, "size=1M");
> + if (!ret)
> + return 0;
> + fprintf(stderr, "Failed to mount tmpfs to %s: %s\n", path, strerror(errno));
> +
> + rmdir(path);
> + return ret;
> +}
> +
> +static int create_mount(int cgv2_fd, int ctid, int id)
> +{
> + int ret = run_in_ve(cgv2_fd, ctid, CLONE_NEWVE, _create_mount, &id);
> + /*
> + * If mount fails, cleanup by free_vfsmnt will be called
> + * via call_rcu, need to wait for update.
> + */
> + sleep(1);
> + return ret;
> +}
> +
> +static int _destroy_mount(void *id_ptr)
> +{
> + char path[PATH_MAX];
> + struct stat st;
> + int id = *(int *)id_ptr;
> +
> + snprintf(path, sizeof(path), TMP_DIR "%d", id);
> +
> + if (stat(path, &st))
> + return 1;
> + if (umount(path)) {
> + fprintf(stderr, "failed to umount directory %s: %s\n", path, strerror(errno));
> + return -1;
> + }
> + if (rmdir(path)) {
> + fprintf(stderr, "failed to remove directory %s: %s\n", path, strerror(errno));
> + return -1;
> + }
> + return 0;
> +}
> +
> +static int destroy_mount(int cgv2_fd, int ctid, int id)
> +{
> + int ret = run_in_ve(cgv2_fd, ctid, CLONE_NEWVE, _destroy_mount, &id);
> + /* free_vfsmnt is called via call_rcu, need to wait for update */
> + sleep(1);
> + return ret;
> +}
> +
> +#define MAX_MNT_ID 32
> +
> +static int get_free_mnt_id(void)
> +{
> + int i;
> + struct stat st;
> + char path[PATH_MAX];
> +
> + for (i = 0; i < MAX_MNT_ID; i++) {
> + snprintf(path, sizeof(path), TMP_DIR "%d", i);
> + if (stat(path, &st))
> + return i;
> + }
> + return -1;
> +}
> +
> +static int get_mount_cost(int cgv2_fd, int ctid)
> +{
> + int avail1, avail2, mnt_id;
> + char path[64];
> +
> + mnt_id = get_free_mnt_id();
> +
> + snprintf(path, sizeof(path), "%d/ve.mnt_avail_nr", ctid);
> + if (mnt_id < 0 ||
> + read_s32_at(cgv2_fd, path, &avail1) ||
> + create_mount(cgv2_fd, ctid, mnt_id) ||
> + read_s32_at(cgv2_fd, path, &avail2) ||
> + destroy_mount(cgv2_fd, ctid, mnt_id))
> + return -1;
> +
> + return avail1 - avail2;
> +}
> +
> +/* Expect mount success and return new avail value */
> +static int mount_and_get_avail(struct __test_metadata *_metadata,
> + int cgv2_fd, int ctid, int mnt_id)
> +{
> + char path_avail[64];
> + int mnt_avail_nr;
> +
> + snprintf(path_avail, sizeof(path_avail), "%d/ve.mnt_avail_nr", ctid);
> +
> + ASSERT_EQ(create_mount(cgv2_fd, ctid, mnt_id), 0);
> + ASSERT_EQ(read_s32_at(cgv2_fd, path_avail, &mnt_avail_nr), 0);
> + return mnt_avail_nr;
> +}
> +
> +/* Expect mount failure and ensure intact avail number */
> +static void assert_mount_fails(struct __test_metadata *_metadata,
> + int cgv2_fd, int ctid, int mnt_id, int avail_count)
> +{
> + char path_avail[64];
> + int mnt_avail_nr;
> +
> + snprintf(path_avail, sizeof(path_avail), "%d/ve.mnt_avail_nr", ctid);
> +
> + ASSERT_EQ(read_s32_at(cgv2_fd, path_avail, &mnt_avail_nr), 0);
> + ASSERT_EQ(mnt_avail_nr, avail_count);
> + ASSERT_LT(create_mount(cgv2_fd, ctid, mnt_id), 0);
> + ASSERT_EQ(read_s32_at(cgv2_fd, path_avail, &mnt_avail_nr), 0);
> + ASSERT_EQ(mnt_avail_nr, avail_count);
> +}
> +
> +FIXTURE(ve_mnt_acc)
> +{
> + int cgv2_fd;
> + int ctid;
> +};
> +
> +FIXTURE_SETUP(ve_mnt_acc)
> +{
> + unsigned long long initial_mnt_avail_nr;
> + char path[64];
> +
> + self->cgv2_fd = mount_cg2_fd();
> + ASSERT_GE(self->cgv2_fd, 0);
> + mkdir(TMP_DIR, 0755);
> +
> + ASSERT_EQ(write_file_at(self->cgv2_fd, "cgroup.subtree_control",
> + VE_CONTROLLERS), 0);
> +
> + self->ctid = make_ve(self->cgv2_fd, CTID_MIN);
> + ASSERT_GE(self->ctid, 0);
> +
> + snprintf(path, sizeof(path), "%d/ve.mnt_max_nr", self->ctid);
> + ASSERT_EQ(write_u64_at(self->cgv2_fd, path, VE_MOUNTS_MAX), 0);
> +
> + /*
> + * The new ve cgroup has not been entered by anything yet, so its
> + * mnt_avail_nr counter should be VE_MOUNTS_MAX.
> + */
> + snprintf(path, sizeof(path), "%d/ve.mnt_avail_nr", self->ctid);
> + ASSERT_EQ(read_u64_at(self->cgv2_fd, path, &initial_mnt_avail_nr), 0);
> + ASSERT_EQ(initial_mnt_avail_nr, VE_MOUNTS_MAX);
> +};
> +
> +FIXTURE_TEARDOWN(ve_mnt_acc)
> +{
Since we mount tmpfs on host mount namespace (we dont pass CLONE_NEWNS),
should we iterate here and umount all the ids that remain mounted after
tests bail? There are maybe places where create_mount is tried and if
assertion fails the mount remains and leaks to the host possibly also
pinning the ve namespace since in ve_try_reserve_mount we get a refcount
on it.
> + destroy_ve(self->cgv2_fd, self->ctid);
> + close(self->cgv2_fd);
> + rmdir(TMP_DIR);
> +}
> +
> +/* Simple test to check mount/umount accounting correctness */
> +TEST_F(ve_mnt_acc, mount_umount)
> +{
> + int original_mnt_avail, mnt_avail_nr;
> + char path[64];
> +
> + snprintf(path, sizeof(path), "%d/ve.mnt_avail_nr", self->ctid);
> +
> + ASSERT_EQ(read_s32_at(self->cgv2_fd, path, &original_mnt_avail), 0);
> +
> + ASSERT_LT(mount_and_get_avail(_metadata, self->cgv2_fd, self->ctid, 0),
> + original_mnt_avail);
> +
> + ASSERT_EQ(destroy_mount(self->cgv2_fd, self->ctid, 0), 0);
> + ASSERT_EQ(read_s32_at(self->cgv2_fd, path, &mnt_avail_nr), 0);
> + ASSERT_EQ(mnt_avail_nr, original_mnt_avail);
> +}
> +
> +/* Test mount limit hits */
> +TEST_F(ve_mnt_acc, hit_limits)
> +{
> + int original_mnt_avail, mnt_avail_nr, mnt_cost;
> + int original_have_mnt;
> + char path_avail[64], path_max_nr[64];
> +
> + snprintf(path_avail, sizeof(path_avail), "%d/ve.mnt_avail_nr", self->ctid);
> + snprintf(path_max_nr, sizeof(path_max_nr), "%d/ve.mnt_max_nr", self->ctid);
> +
> + mnt_cost = get_mount_cost(self->cgv2_fd, self->ctid);
> + ASSERT_GE(mnt_cost, 1);
> +
> + ASSERT_EQ(read_s32_at(self->cgv2_fd, path_avail, &original_mnt_avail), 0);
> + original_have_mnt = VE_MOUNTS_MAX - original_mnt_avail;
> +
> + /* Step 1: reduce number of available mounts to mnt_cost */
> + ASSERT_EQ(write_u64_at(self->cgv2_fd, path_max_nr, original_have_mnt + 1 * mnt_cost), 0);
> + ASSERT_EQ(read_s32_at(self->cgv2_fd, path_avail, &mnt_avail_nr), 0);
> + ASSERT_EQ(mnt_avail_nr, 1 * mnt_cost);
> +
> + /* Step 2: do one mount, no mounts should be available */
> + ASSERT_EQ(mount_and_get_avail(_metadata, self->cgv2_fd, self->ctid, 0),
> + 0);
> +
> + /* Step 3: check that one more mount falils */
> + assert_mount_fails(_metadata, self->cgv2_fd, self->ctid, 1, 0);
> +
> + /* Step 4: increase mount limit a little bit, mount should still fail */
> + ASSERT_EQ(write_u64_at(self->cgv2_fd, path_max_nr,
> + original_have_mnt + 2 * mnt_cost - 1), 0);
> + assert_mount_fails(_metadata, self->cgv2_fd, self->ctid, 1, mnt_cost - 1);
> +
> + /* Step 5: increase by 1 and win now */
> + ASSERT_EQ(write_u64_at(self->cgv2_fd, path_max_nr, original_have_mnt + 2 * mnt_cost), 0);
> + ASSERT_EQ(read_s32_at(self->cgv2_fd, path_avail, &mnt_avail_nr), 0);
> + ASSERT_EQ(mnt_avail_nr, mnt_cost);
> +
> + ASSERT_EQ(mount_and_get_avail(_metadata, self->cgv2_fd, self->ctid, 1),
> + 0);
> +
> + /* Step 6: reduce mnt_max_nr so we have more mounts than allowed */
> + ASSERT_EQ(write_u64_at(self->cgv2_fd, path_max_nr, original_have_mnt + 1 * mnt_cost), 0);
> + ASSERT_EQ(read_s32_at(self->cgv2_fd, path_avail, &mnt_avail_nr), 0);
> + ASSERT_EQ(mnt_avail_nr, -1 * mnt_cost);
> +
> + /* Step 7: try to do mount when avail < 0, ensure number is intact */
> + assert_mount_fails(_metadata, self->cgv2_fd, self->ctid, 2, -1 * mnt_cost);
> +
> + /* Step 8: remove one mount, check avail value update, mount should fail */
> + ASSERT_EQ(destroy_mount(self->cgv2_fd, self->ctid, 0), 0);
> + assert_mount_fails(_metadata, self->cgv2_fd, self->ctid, 2, 0);
> +
> + /* Step 9: remove one more mount and check that new mount succeeds */
> + ASSERT_EQ(destroy_mount(self->cgv2_fd, self->ctid, 1), 0);
> + ASSERT_EQ(read_s32_at(self->cgv2_fd, path_avail, &mnt_avail_nr), 0);
> + ASSERT_EQ(mnt_avail_nr, 1 * mnt_cost);
> + ASSERT_EQ(mount_and_get_avail(_metadata, self->cgv2_fd, self->ctid, 2),
> + 0);
> +
> + ASSERT_EQ(destroy_mount(self->cgv2_fd, self->ctid, 2), 0);
> +}
> +
> +/*
> + * Mount propagation makes one mount cost more.
> + * This test check that if we run out or mounts in the middle of creating
> + * a new one, everything is restored smoothly and nothing leaks.
> + */
> +TEST_F(ve_mnt_acc, partial_mounts)
> +{
> + char path_avail[64], path_max_nr[64];
> + int mount_cost, i, orig_have, orig_mnt_avail;
> +
> + snprintf(path_max_nr, sizeof(path_max_nr), "%d/ve.mnt_max_nr", self->ctid);
> + snprintf(path_avail, sizeof(path_avail), "%d/ve.mnt_avail_nr", self->ctid);
> +
> + mount_cost = get_mount_cost(self->cgv2_fd, self->ctid);
> + ASSERT_GE(mount_cost, 1);
> + ASSERT_EQ(read_s32_at(self->cgv2_fd, path_avail, &orig_mnt_avail), 0);
> + orig_have = VE_MOUNTS_MAX - orig_mnt_avail;
> +
> + if (mount_cost == 1)
> + SKIP(return, "mount cost is 1, no partial mounts possible");
> +
> + for (i = 0; i < mount_cost; i++) {
> + ASSERT_EQ(write_u64_at(self->cgv2_fd, path_max_nr, orig_have + i), 0);
> + assert_mount_fails(_metadata, self->cgv2_fd, self->ctid, 0, i);
> + }
> +}
> +
> +/* Test that pseudosuper allows negative avail with correct accounting. */
> +TEST_F(ve_mnt_acc, pseudosuper_allows_overuse)
> +{
> + int orig_mnt_avail, orig_have;
> + int mount_cost;
> + char path_avail[64], path_max_nr[64];
> +
> + snprintf(path_max_nr, sizeof(path_max_nr), "%d/ve.mnt_max_nr", self->ctid);
> + snprintf(path_avail, sizeof(path_avail), "%d/ve.mnt_avail_nr", self->ctid);
> + ASSERT_EQ(read_s32_at(self->cgv2_fd, path_avail, &orig_mnt_avail), 0);
> + orig_have = VE_MOUNTS_MAX - orig_mnt_avail;
> +
> + mount_cost = get_mount_cost(self->cgv2_fd, self->ctid);
> + ASSERT_GE(mount_cost, 1);
> +
> + ASSERT_EQ(write_u64_at(self->cgv2_fd, path_max_nr, orig_have + mount_cost), 0);
> + ASSERT_EQ(set_pseudosuper(self->cgv2_fd, self->ctid, 1), 0);
> +
> + ASSERT_EQ(mount_and_get_avail(_metadata, self->cgv2_fd, self->ctid, 0),
> + 0);
> + ASSERT_EQ(mount_and_get_avail(_metadata, self->cgv2_fd, self->ctid, 1),
> + -1 * mount_cost);
> +
> + ASSERT_EQ(set_pseudosuper(self->cgv2_fd, self->ctid, 0), 0);
> +
> + assert_mount_fails(_metadata, self->cgv2_fd, self->ctid, 2, -1 * mount_cost);
> + ASSERT_EQ(destroy_mount(self->cgv2_fd, self->ctid, 0), 0);
> + assert_mount_fails(_metadata, self->cgv2_fd, self->ctid, 2, 0);
> + ASSERT_EQ(destroy_mount(self->cgv2_fd, self->ctid, 1), 0);
> + ASSERT_EQ(get_mount_cost(self->cgv2_fd, self->ctid), mount_cost);
> +}
> +
> +/* Test that pseudosuper doesn't disable accounting. */
> +TEST_F(ve_mnt_acc, pseudosuper_continues_accounting)
> +{
> + int orig_mnt_avail, mount_cost, mnt_avail_nr;
> + char path_avail[64];
> +
> + snprintf(path_avail, sizeof(path_avail), "%d/ve.mnt_avail_nr", self->ctid);
> +
> + ASSERT_EQ(read_s32_at(self->cgv2_fd, path_avail, &orig_mnt_avail), 0);
> + mount_cost = get_mount_cost(self->cgv2_fd, self->ctid);
> + ASSERT_GE(mount_cost, 1);
> +
> + ASSERT_EQ(set_pseudosuper(self->cgv2_fd, self->ctid, 0), 0);
> +
> + /* mnt 0 - mounted without pseudosuper, umounted with it. */
> + ASSERT_EQ(mount_and_get_avail(_metadata, self->cgv2_fd, self->ctid, 0),
> + orig_mnt_avail - mount_cost);
> + ASSERT_EQ(set_pseudosuper(self->cgv2_fd, self->ctid, 1), 0);
> +
> + /* Cost is the same when mount/umount happen under pseudosuper. */
> + ASSERT_EQ(get_mount_cost(self->cgv2_fd, self->ctid), mount_cost);
> +
> + /* mnt 1 - mounted with pseudosuper, umounted without it. */
> + ASSERT_EQ(mount_and_get_avail(_metadata, self->cgv2_fd, self->ctid, 1),
> + orig_mnt_avail - 2 * mount_cost);
> +
> + ASSERT_EQ(destroy_mount(self->cgv2_fd, self->ctid, 0), 0);
> + ASSERT_EQ(read_s32_at(self->cgv2_fd, path_avail, &mnt_avail_nr), 0);
> + ASSERT_EQ(mnt_avail_nr, orig_mnt_avail - mount_cost);
> +
> + ASSERT_EQ(set_pseudosuper(self->cgv2_fd, self->ctid, 0), 0);
> +
> + ASSERT_EQ(destroy_mount(self->cgv2_fd, self->ctid, 1), 0);
> + ASSERT_EQ(read_s32_at(self->cgv2_fd, path_avail, &mnt_avail_nr), 0);
> + ASSERT_EQ(mnt_avail_nr, orig_mnt_avail);
> +}
> +
> +/* Test failcount feature */
> +TEST_F(ve_mnt_acc, failcount)
> +{
> + char path_fc[64], failcount_str[512], path_max_nr[64];
> +
> + snprintf(path_fc, sizeof(path_fc), "%d/ve.failcount", self->ctid);
> + snprintf(path_max_nr, sizeof(path_max_nr), "%d/ve.mnt_max_nr", self->ctid);
> +
> + ASSERT_GE(read_file_at(self->cgv2_fd, path_fc,
> + failcount_str, sizeof(failcount_str)), 0);
> + ASSERT_TRUE(strstr(failcount_str, "mnt: 0\n") != NULL);
> +
> + /* Check successful mount doesn't affect failcount */
> + mount_and_get_avail(_metadata, self->cgv2_fd, self->ctid, 0);
> + ASSERT_GE(read_file_at(self->cgv2_fd, path_fc,
> + failcount_str, sizeof(failcount_str)), 0);
> + ASSERT_TRUE(strstr(failcount_str, "mnt: 0\n") != NULL);
> + ASSERT_EQ(destroy_mount(self->cgv2_fd, self->ctid, 0), 0);
> +
> + /* Check failcount update when mount fails */
> + ASSERT_EQ(write_u64_at(self->cgv2_fd, path_max_nr, 0), 0);
> + ASSERT_LT(create_mount(self->cgv2_fd, self->ctid, 1), 0);
> + ASSERT_GE(read_file_at(self->cgv2_fd, path_fc,
> + failcount_str, sizeof(failcount_str)), 0);
> + ASSERT_TRUE(strstr(failcount_str, "mnt: 1\n") != NULL);
> +
> + /* Check failcount flush */
> + ASSERT_EQ(write_u64_at(self->cgv2_fd, path_fc, 0), 0);
> + ASSERT_GE(read_file_at(self->cgv2_fd, path_fc,
> + failcount_str, sizeof(failcount_str)), 0);
> + ASSERT_TRUE(strstr(failcount_str, "mnt: 0\n") != NULL);
> +
> + /* Check failcount update when mount fails again */
> + ASSERT_EQ(write_u64_at(self->cgv2_fd, path_max_nr, 0), 0);
> + ASSERT_LT(create_mount(self->cgv2_fd, self->ctid, 1), 0);
> + ASSERT_GE(read_file_at(self->cgv2_fd, path_fc,
> + failcount_str, sizeof(failcount_str)), 0);
> + ASSERT_TRUE(strstr(failcount_str, "mnt: 1\n") != NULL);
> +}
> +
> +TEST_HARNESS_MAIN
--
Best regards, Vasileios Almpanis
Software Developer, Virtuozzo.
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