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Systemd/src/shared/loop-util.c

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/* SPDX-License-Identifier: LGPL-2.1+ */
#if HAVE_VALGRIND_MEMCHECK_H
#include <valgrind/memcheck.h>
#endif
#include <errno.h>
#include <fcntl.h>
#include <linux/blkpg.h>
#include <linux/fs.h>
#include <linux/loop.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include "alloc-util.h"
#include "blockdev-util.h"
#include "errno-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "loop-util.h"
#include "missing_loop.h"
#include "parse-util.h"
#include "stat-util.h"
#include "stdio-util.h"
#include "string-util.h"
static void cleanup_clear_loop_close(int *fd) {
if (*fd < 0)
return;
(void) ioctl(*fd, LOOP_CLR_FD);
(void) safe_close(*fd);
}
static int loop_configure(int fd, const struct loop_config *c) {
int r;
assert(fd >= 0);
assert(c);
if (ioctl(fd, LOOP_CONFIGURE, c) < 0) {
/* Do fallback only if LOOP_CONFIGURE is not supported, propagate all other errors. Note that
* the kernel is weird: non-existing ioctls currently return EINVAL rather than ENOTTY on
* loopback block devices. They should fix that in the kernel, but in the meantime we accept
* both here. */
if (!ERRNO_IS_NOT_SUPPORTED(errno) && errno != EINVAL)
return -errno;
} else {
if (!FLAGS_SET(c->info.lo_flags, LO_FLAGS_PARTSCAN))
return 0;
/* Kernel 5.8 vanilla doesn't properly propagate the partition scanning flag into the
* block device. Let's hence verify if things work correctly here before returning. */
r = blockdev_partscan_enabled(fd);
if (r < 0)
goto fail;
if (r > 0)
return 0; /* All is good. */
/* Otherwise, undo the attachment and use the old APIs */
(void) ioctl(fd, LOOP_CLR_FD);
}
if (ioctl(fd, LOOP_SET_FD, c->fd) < 0)
return -errno;
if (ioctl(fd, LOOP_SET_STATUS64, &c->info) < 0) {
r = -errno;
goto fail;
}
return 0;
fail:
(void) ioctl(fd, LOOP_CLR_FD);
return r;
}
int loop_device_make(
int fd,
int open_flags,
uint64_t offset,
uint64_t size,
uint32_t loop_flags,
LoopDevice **ret) {
_cleanup_free_ char *loopdev = NULL;
struct loop_config config;
LoopDevice *d = NULL;
struct stat st;
int nr = -1, r;
assert(fd >= 0);
assert(ret);
assert(IN_SET(open_flags, O_RDWR, O_RDONLY));
if (fstat(fd, &st) < 0)
return -errno;
if (S_ISBLK(st.st_mode)) {
if (ioctl(fd, LOOP_GET_STATUS64, &config.info) >= 0) {
/* Oh! This is a loopback device? That's interesting! */
#if HAVE_VALGRIND_MEMCHECK_H
/* Valgrind currently doesn't know LOOP_GET_STATUS64. Remove this once it does */
VALGRIND_MAKE_MEM_DEFINED(&config.info, sizeof(config.info));
#endif
nr = config.info.lo_number;
if (asprintf(&loopdev, "/dev/loop%i", nr) < 0)
return -ENOMEM;
}
if (offset == 0 && IN_SET(size, 0, UINT64_MAX)) {
_cleanup_close_ int copy = -1;
/* If this is already a block device, store a copy of the fd as it is */
copy = fcntl(fd, F_DUPFD_CLOEXEC, 3);
if (copy < 0)
return -errno;
d = new(LoopDevice, 1);
if (!d)
return -ENOMEM;
*d = (LoopDevice) {
.fd = TAKE_FD(copy),
.nr = nr,
.node = TAKE_PTR(loopdev),
.relinquished = true, /* It's not allocated by us, don't destroy it when this object is freed */
};
*ret = d;
return d->fd;
}
} else {
r = stat_verify_regular(&st);
if (r < 0)
return r;
}
_cleanup_close_ int control = -1;
_cleanup_(cleanup_clear_loop_close) int loop_with_fd = -1;
control = open("/dev/loop-control", O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
if (control < 0)
return -errno;
config = (struct loop_config) {
.fd = fd,
.info = {
/* Use the specified flags, but configure the read-only flag from the open flags, and force autoclear */
.lo_flags = (loop_flags & ~LO_FLAGS_READ_ONLY) | ((loop_flags & O_ACCMODE) == O_RDONLY ? LO_FLAGS_READ_ONLY : 0) | LO_FLAGS_AUTOCLEAR,
.lo_offset = offset,
.lo_sizelimit = size == UINT64_MAX ? 0 : size,
},
};
/* Loop around LOOP_CTL_GET_FREE, since at the moment we attempt to open the returned device it might
* be gone already, taken by somebody else racing against us. */
for (unsigned n_attempts = 0;;) {
_cleanup_close_ int loop = -1;
nr = ioctl(control, LOOP_CTL_GET_FREE);
if (nr < 0)
return -errno;
if (asprintf(&loopdev, "/dev/loop%i", nr) < 0)
return -ENOMEM;
loop = open(loopdev, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|open_flags);
if (loop < 0) {
/* Somebody might've gotten the same number from the kernel, used the device,
* and called LOOP_CTL_REMOVE on it. Let's retry with a new number. */
if (errno != ENOENT)
return -errno;
} else {
r = loop_configure(loop, &config);
if (r >= 0) {
loop_with_fd = TAKE_FD(loop);
break;
}
if (r != -EBUSY)
return r;
}
if (++n_attempts >= 64) /* Give up eventually */
return -EBUSY;
loopdev = mfree(loopdev);
}
d = new(LoopDevice, 1);
if (!d)
return -ENOMEM;
*d = (LoopDevice) {
.fd = TAKE_FD(loop_with_fd),
.node = TAKE_PTR(loopdev),
.nr = nr,
};
*ret = d;
return 0;
}
int loop_device_make_by_path(const char *path, int open_flags, uint32_t loop_flags, LoopDevice **ret) {
_cleanup_close_ int fd = -1;
int r;
assert(path);
assert(ret);
assert(open_flags < 0 || IN_SET(open_flags, O_RDWR, O_RDONLY));
/* Passing < 0 as open_flags here means we'll try to open the device writable if we can, retrying
* read-only if we cannot. */
fd = open(path, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|(open_flags >= 0 ? open_flags : O_RDWR));
if (fd < 0) {
r = -errno;
/* Retry read-only? */
if (open_flags >= 0 || !(ERRNO_IS_PRIVILEGE(r) || r == -EROFS))
return r;
fd = open(path, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|O_RDONLY);
if (fd < 0)
return r; /* Propagate original error */
open_flags = O_RDONLY;
} else if (open_flags < 0)
open_flags = O_RDWR;
return loop_device_make(fd, open_flags, 0, 0, loop_flags, ret);
}
LoopDevice* loop_device_unref(LoopDevice *d) {
if (!d)
return NULL;
if (d->fd >= 0) {
/* Implicitly sync the device, since otherwise in-flight blocks might not get written */
if (fsync(d->fd) < 0)
log_debug_errno(errno, "Failed to sync loop block device, ignoring: %m");
if (d->nr >= 0 && !d->relinquished) {
if (ioctl(d->fd, LOOP_CLR_FD) < 0)
log_debug_errno(errno, "Failed to clear loop device: %m");
}
safe_close(d->fd);
}
if (d->nr >= 0 && !d->relinquished) {
_cleanup_close_ int control = -1;
control = open("/dev/loop-control", O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
if (control < 0)
log_warning_errno(errno,
"Failed to open loop control device, cannot remove loop device %s: %m",
strna(d->node));
else
for (unsigned n_attempts = 0;;) {
if (ioctl(control, LOOP_CTL_REMOVE, d->nr) >= 0)
break;
if (errno != EBUSY || ++n_attempts >= 64) {
log_warning_errno(errno, "Failed to remove device %s: %m", strna(d->node));
break;
}
(void) usleep(50 * USEC_PER_MSEC);
}
}
free(d->node);
return mfree(d);
}
void loop_device_relinquish(LoopDevice *d) {
assert(d);
/* Don't attempt to clean up the loop device anymore from this point on. Leave the clean-ing up to the kernel
* itself, using the loop device "auto-clear" logic we already turned on when creating the device. */
d->relinquished = true;
}
int loop_device_open(const char *loop_path, int open_flags, LoopDevice **ret) {
_cleanup_close_ int loop_fd = -1;
_cleanup_free_ char *p = NULL;
struct loop_info64 info;
struct stat st;
LoopDevice *d;
int nr;
assert(loop_path);
assert(ret);
loop_fd = open(loop_path, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|open_flags);
if (loop_fd < 0)
return -errno;
if (fstat(loop_fd, &st) < 0)
return -errno;
if (!S_ISBLK(st.st_mode))
return -ENOTBLK;
if (ioctl(loop_fd, LOOP_GET_STATUS64, &info) >= 0) {
#if HAVE_VALGRIND_MEMCHECK_H
/* Valgrind currently doesn't know LOOP_GET_STATUS64. Remove this once it does */
VALGRIND_MAKE_MEM_DEFINED(&info, sizeof(info));
#endif
nr = info.lo_number;
} else
nr = -1;
p = strdup(loop_path);
if (!p)
return -ENOMEM;
d = new(LoopDevice, 1);
if (!d)
return -ENOMEM;
*d = (LoopDevice) {
.fd = TAKE_FD(loop_fd),
.nr = nr,
.node = TAKE_PTR(p),
.relinquished = true, /* It's not ours, don't try to destroy it when this object is freed */
};
*ret = d;
return d->fd;
}
static int resize_partition(int partition_fd, uint64_t offset, uint64_t size) {
char sysfs[STRLEN("/sys/dev/block/:/partition") + 2*DECIMAL_STR_MAX(dev_t) + 1];
_cleanup_free_ char *whole = NULL, *buffer = NULL;
uint64_t current_offset, current_size, partno;
_cleanup_close_ int whole_fd = -1;
struct stat st;
dev_t devno;
int r;
assert(partition_fd >= 0);
/* Resizes the partition the loopback device refer to (assuming it refers to one instead of an actual
* loopback device), and changes the offset, if needed. This is a fancy wrapper around
* BLKPG_RESIZE_PARTITION. */
if (fstat(partition_fd, &st) < 0)
return -errno;
assert(S_ISBLK(st.st_mode));
xsprintf(sysfs, "/sys/dev/block/%u:%u/partition", major(st.st_rdev), minor(st.st_rdev));
r = read_one_line_file(sysfs, &buffer);
if (r == -ENOENT) /* not a partition, cannot resize */
return -ENOTTY;
if (r < 0)
return r;
r = safe_atou64(buffer, &partno);
if (r < 0)
return r;
xsprintf(sysfs, "/sys/dev/block/%u:%u/start", major(st.st_rdev), minor(st.st_rdev));
buffer = mfree(buffer);
r = read_one_line_file(sysfs, &buffer);
if (r < 0)
return r;
r = safe_atou64(buffer, &current_offset);
if (r < 0)
return r;
if (current_offset > UINT64_MAX/512U)
return -EINVAL;
current_offset *= 512U;
if (ioctl(partition_fd, BLKGETSIZE64, &current_size) < 0)
return -EINVAL;
if (size == UINT64_MAX && offset == UINT64_MAX)
return 0;
if (current_size == size && current_offset == offset)
return 0;
xsprintf(sysfs, "/sys/dev/block/%u:%u/../dev", major(st.st_rdev), minor(st.st_rdev));
buffer = mfree(buffer);
r = read_one_line_file(sysfs, &buffer);
if (r < 0)
return r;
r = parse_dev(buffer, &devno);
if (r < 0)
return r;
r = device_path_make_major_minor(S_IFBLK, devno, &whole);
if (r < 0)
return r;
whole_fd = open(whole, O_RDWR|O_CLOEXEC|O_NONBLOCK|O_NOCTTY);
if (whole_fd < 0)
return -errno;
struct blkpg_partition bp = {
.pno = partno,
.start = offset == UINT64_MAX ? current_offset : offset,
.length = size == UINT64_MAX ? current_size : size,
};
struct blkpg_ioctl_arg ba = {
.op = BLKPG_RESIZE_PARTITION,
.data = &bp,
.datalen = sizeof(bp),
};
if (ioctl(whole_fd, BLKPG, &ba) < 0)
return -errno;
return 0;
}
int loop_device_refresh_size(LoopDevice *d, uint64_t offset, uint64_t size) {
struct loop_info64 info;
assert(d);
/* Changes the offset/start of the loop device relative to the beginning of the underlying file or
* block device. If this loop device actually refers to a partition and not a loopback device, we'll
* try to adjust the partition offsets instead.
*
* If either offset or size is UINT64_MAX we won't change that parameter. */
if (d->fd < 0)
return -EBADF;
if (d->nr < 0) /* not a loopback device */
return resize_partition(d->fd, offset, size);
if (ioctl(d->fd, LOOP_GET_STATUS64, &info) < 0)
return -errno;
#if HAVE_VALGRIND_MEMCHECK_H
/* Valgrind currently doesn't know LOOP_GET_STATUS64. Remove this once it does */
VALGRIND_MAKE_MEM_DEFINED(&info, sizeof(info));
#endif
if (size == UINT64_MAX && offset == UINT64_MAX)
return 0;
if (info.lo_sizelimit == size && info.lo_offset == offset)
return 0;
if (size != UINT64_MAX)
info.lo_sizelimit = size;
if (offset != UINT64_MAX)
info.lo_offset = offset;
if (ioctl(d->fd, LOOP_SET_STATUS64, &info) < 0)
return -errno;
return 0;
}
int loop_device_flock(LoopDevice *d, int operation) {
assert(d);
if (d->fd < 0)
return -EBADF;
if (flock(d->fd, operation) < 0)
return -errno;
return 0;
}
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