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// SPDX-License-Identifier: GPL-2.0
/*
* Thawing a superblock behind the block layer's back.
*
* A device-mapper suspend freezes the filesystem on the device through
* bdev_freeze() with the same userspace holder FIFREEZE uses, so FITHAW can
* drop that freeze while the device is still suspended. The resume then
* finds nothing left to thaw. Check that it still thaws the device so that
* it can be mounted again afterwards. The filesystem is mounted read-only
* so the freeze and the thaw don't need to write to the suspended device.
*/
#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <linux/dm-ioctl.h>
#include <linux/fs.h>
#include <sched.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <unistd.h>
#include "../../kselftest_harness.h"
#include "loop_util.h"
#define IMG_SIZE (64 << 20)
FIXTURE(bdev_thaw) {
char dir[64];
char img[96];
char mnt[96];
char node[96];
char name[32];
int loop;
int mntfd;
bool tmpfs;
bool dm;
bool suspended;
bool mounted;
};
static int dm_ioctl(unsigned long cmd, const char *name, uint32_t flags, dev_t *dev)
{
struct dm_ioctl dmi = {
.version = { DM_VERSION_MAJOR, 0, 0 },
.data_size = sizeof(dmi),
.data_start = sizeof(dmi),
.flags = flags,
};
int fd, ret = 0;
strncpy(dmi.name, name, sizeof(dmi.name) - 1);
fd = open("/dev/mapper/control", O_RDWR | O_CLOEXEC);
if (fd < 0)
return -errno;
if (ioctl(fd, cmd, &dmi))
ret = -errno;
else if (dev)
*dev = makedev((dmi.dev >> 8) & 0xfff,
(dmi.dev & 0xff) | ((dmi.dev >> 12) & 0xfff00));
close(fd);
return ret;
}
/* Remove @name now, or on its last close if udev still has it open. */
static int dm_remove(const char *name)
{
return dm_ioctl(DM_DEV_REMOVE, name, DM_DEFERRED_REMOVE, NULL);
}
/* Create @name as a linear mapping of all of @backing and make it live. */
static int dm_create_linear(const char *name, dev_t backing, uint64_t sectors,
dev_t *dev)
{
struct {
struct dm_ioctl dmi;
struct dm_target_spec spec;
char params[64];
} __attribute__((aligned(8))) t = {};
int fd, ret;
ret = dm_ioctl(DM_DEV_CREATE, name, 0, NULL);
if (ret)
return ret;
t.dmi.version[0] = DM_VERSION_MAJOR;
t.dmi.data_size = sizeof(t);
t.dmi.data_start = sizeof(t.dmi);
t.dmi.target_count = 1;
strncpy(t.dmi.name, name, sizeof(t.dmi.name) - 1);
t.spec.length = sectors;
strcpy(t.spec.target_type, "linear");
snprintf(t.params, sizeof(t.params), "%u:%u 0", major(backing), minor(backing));
fd = open("/dev/mapper/control", O_RDWR | O_CLOEXEC);
if (fd >= 0) {
ret = ioctl(fd, DM_TABLE_LOAD, &t) ? -errno : 0;
close(fd);
} else {
ret = -errno;
}
/* Resuming makes the loaded table live. */
if (!ret)
ret = dm_ioctl(DM_DEV_SUSPEND, name, 0, dev);
if (ret)
dm_remove(name);
return ret;
}
static void bdev_thaw_cleanup(FIXTURE_DATA(bdev_thaw) *self)
{
if (self->suspended)
dm_ioctl(DM_DEV_SUSPEND, self->name, 0, NULL);
if (self->mntfd >= 0)
close(self->mntfd);
if (self->mounted)
umount2(self->mnt, MNT_DETACH);
if (self->dm)
dm_remove(self->name);
if (self->loop >= 0)
loop_clear(self->loop);
unlink(self->node);
unlink(self->img);
rmdir(self->mnt);
if (self->tmpfs)
umount2(self->dir, MNT_DETACH);
rmdir(self->dir);
}
FIXTURE_SETUP(bdev_thaw)
{
char cmd[160], dev[32];
struct stat st;
dev_t dmdev;
int fd, ret;
self->loop = -1;
self->mntfd = -1;
self->tmpfs = false;
self->dm = false;
self->suspended = false;
self->mounted = false;
if (geteuid() != 0)
SKIP(return, "test requires CAP_SYS_ADMIN");
if (access("/dev/loop-control", R_OK | W_OK))
SKIP(return, "test requires loop devices");
if (access("/dev/mapper/control", R_OK | W_OK))
SKIP(return, "test requires device-mapper");
ASSERT_EQ(unshare(CLONE_NEWNS), 0);
ASSERT_EQ(mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, NULL), 0);
snprintf(self->dir, sizeof(self->dir), "/tmp/bdev_thaw.XXXXXX");
ASSERT_NE(mkdtemp(self->dir), NULL);
/* /tmp may be mounted nodev, the dm node needs a tmpfs of our own. */
ASSERT_EQ(mount("tmpfs", self->dir, "tmpfs", MS_NOSUID | MS_NOEXEC, NULL), 0)
rmdir(self->dir);
self->tmpfs = true;
snprintf(self->img, sizeof(self->img), "%s/img", self->dir);
snprintf(self->mnt, sizeof(self->mnt), "%s/mnt", self->dir);
snprintf(self->node, sizeof(self->node), "%s/dm", self->dir);
snprintf(self->name, sizeof(self->name), "bdev_thaw_%d", getpid());
/* The harness doesn't run the teardown when the setup fails. */
ASSERT_EQ(mkdir(self->mnt, 0700), 0)
bdev_thaw_cleanup(self);
fd = open(self->img, O_RDWR | O_CREAT | O_CLOEXEC, 0600);
ASSERT_GE(fd, 0)
bdev_thaw_cleanup(self);
ASSERT_EQ(ftruncate(fd, IMG_SIZE), 0)
bdev_thaw_cleanup(self);
snprintf(cmd, sizeof(cmd), "mkfs.ext4 -q -F %s >/dev/null 2>&1", self->img);
ret = system(cmd);
if (ret) {
close(fd);
bdev_thaw_cleanup(self);
SKIP(return, "mkfs.ext4 failed or is not available");
}
self->loop = loop_bind(fd);
close(fd);
if (loop_missing(self->loop)) {
bdev_thaw_cleanup(self);
SKIP(return, "test requires loop devices");
}
ASSERT_GE(self->loop, 0)
bdev_thaw_cleanup(self);
snprintf(dev, sizeof(dev), "/dev/loop%d", self->loop);
ASSERT_EQ(stat(dev, &st), 0)
bdev_thaw_cleanup(self);
ASSERT_EQ(dm_create_linear(self->name, st.st_rdev, IMG_SIZE >> 9, &dmdev), 0)
bdev_thaw_cleanup(self);
self->dm = true;
ASSERT_EQ(mknod(self->node, S_IFBLK | 0600, dmdev), 0)
bdev_thaw_cleanup(self);
if (mount(self->node, self->mnt, "ext4", MS_RDONLY, NULL)) {
if (errno == ENODEV) {
bdev_thaw_cleanup(self);
SKIP(return, "kernel lacks ext4");
}
ASSERT_EQ(errno, 0)
bdev_thaw_cleanup(self);
}
self->mounted = true;
self->mntfd = open(self->mnt, O_RDONLY | O_DIRECTORY | O_CLOEXEC);
ASSERT_GE(self->mntfd, 0)
bdev_thaw_cleanup(self);
}
FIXTURE_TEARDOWN(bdev_thaw)
{
bdev_thaw_cleanup(self);
}
TEST_F(bdev_thaw, fithaw_during_dm_suspend)
{
/* A suspend with lockfs freezes the filesystem through bdev_freeze(). */
ASSERT_EQ(dm_ioctl(DM_DEV_SUSPEND, self->name, DM_SUSPEND_FLAG, NULL), 0);
self->suspended = true;
/* FITHAW drops the freeze the suspend holds. */
if (ioctl(self->mntfd, FITHAW, 0)) {
ASSERT_EQ(errno, EINVAL);
SKIP(return, "FITHAW doesn't drop a device-mapper freeze");
}
/* The resume's bdev_thaw() finds nothing left to thaw. */
ASSERT_EQ(dm_ioctl(DM_DEV_SUSPEND, self->name, 0, NULL), 0);
self->suspended = false;
close(self->mntfd);
self->mntfd = -1;
ASSERT_EQ(umount2(self->mnt, 0), 0);
self->mounted = false;
ASSERT_EQ(mount(self->node, self->mnt, "ext4", MS_RDONLY, NULL), 0)
TH_LOG("device still frozen after the resume: %s", strerror(errno));
self->mounted = true;
}
TEST_HARNESS_MAIN
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