1b49e3e3c4
As suggested in https://github.com/systemd/systemd/pull/14261#pullrequestreview-332398625.
405 lines
13 KiB
C
405 lines
13 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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#if HAVE_VALGRIND_MEMCHECK_H
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#include <valgrind/memcheck.h>
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#endif
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#include <errno.h>
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#include <fcntl.h>
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#include <linux/blkpg.h>
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#include <linux/fs.h>
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#include <linux/loop.h>
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#include <sys/file.h>
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#include <sys/ioctl.h>
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#include <unistd.h>
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#include "alloc-util.h"
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#include "fd-util.h"
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#include "fileio.h"
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#include "loop-util.h"
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#include "parse-util.h"
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#include "stat-util.h"
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#include "stdio-util.h"
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#include "string-util.h"
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static void cleanup_clear_loop_close(int *fd) {
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if (*fd >= 0) {
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(void) ioctl(*fd, LOOP_CLR_FD);
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(void) safe_close(*fd);
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}
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}
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int loop_device_make(
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int fd,
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int open_flags,
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uint64_t offset,
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uint64_t size,
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uint32_t loop_flags,
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LoopDevice **ret) {
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_cleanup_free_ char *loopdev = NULL;
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struct loop_info64 info;
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LoopDevice *d = NULL;
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struct stat st;
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int nr = -1, r;
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assert(fd >= 0);
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assert(ret);
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assert(IN_SET(open_flags, O_RDWR, O_RDONLY));
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if (fstat(fd, &st) < 0)
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return -errno;
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if (S_ISBLK(st.st_mode)) {
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if (ioctl(fd, LOOP_GET_STATUS64, &info) >= 0) {
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/* Oh! This is a loopback device? That's interesting! */
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#if HAVE_VALGRIND_MEMCHECK_H
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/* Valgrind currently doesn't know LOOP_GET_STATUS64. Remove this once it does */
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VALGRIND_MAKE_MEM_DEFINED(&info, sizeof(info));
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#endif
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nr = info.lo_number;
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if (asprintf(&loopdev, "/dev/loop%i", nr) < 0)
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return -ENOMEM;
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}
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if (offset == 0 && IN_SET(size, 0, UINT64_MAX)) {
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_cleanup_close_ int copy = -1;
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/* If this is already a block device, store a copy of the fd as it is */
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copy = fcntl(fd, F_DUPFD_CLOEXEC, 3);
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if (copy < 0)
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return -errno;
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d = new(LoopDevice, 1);
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if (!d)
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return -ENOMEM;
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*d = (LoopDevice) {
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.fd = TAKE_FD(copy),
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.nr = nr,
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.node = TAKE_PTR(loopdev),
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.relinquished = true, /* It's not allocated by us, don't destroy it when this object is freed */
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};
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*ret = d;
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return d->fd;
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}
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} else {
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r = stat_verify_regular(&st);
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if (r < 0)
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return r;
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}
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_cleanup_close_ int control = -1;
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_cleanup_(cleanup_clear_loop_close) int loop_with_fd = -1;
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control = open("/dev/loop-control", O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
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if (control < 0)
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return -errno;
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/* Loop around LOOP_CTL_GET_FREE, since at the moment we attempt to open the returned device it might
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* be gone already, taken by somebody else racing against us. */
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for (unsigned n_attempts = 0;;) {
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_cleanup_close_ int loop = -1;
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nr = ioctl(control, LOOP_CTL_GET_FREE);
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if (nr < 0)
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return -errno;
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if (asprintf(&loopdev, "/dev/loop%i", nr) < 0)
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return -ENOMEM;
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loop = open(loopdev, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|open_flags);
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if (loop < 0) {
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/* Somebody might've gotten the same number from the kernel, used the device,
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* and called LOOP_CTL_REMOVE on it. Let's retry with a new number. */
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if (errno != ENOENT)
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return -errno;
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} else {
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if (ioctl(loop, LOOP_SET_FD, fd) >= 0) {
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loop_with_fd = TAKE_FD(loop);
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break;
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}
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if (errno != EBUSY)
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return -errno;
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}
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if (++n_attempts >= 64) /* Give up eventually */
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return -EBUSY;
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loopdev = mfree(loopdev);
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}
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info = (struct loop_info64) {
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/* Use the specified flags, but configure the read-only flag from the open flags, and force autoclear */
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.lo_flags = (loop_flags & ~LO_FLAGS_READ_ONLY) | ((loop_flags & O_ACCMODE) == O_RDONLY ? LO_FLAGS_READ_ONLY : 0) | LO_FLAGS_AUTOCLEAR,
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.lo_offset = offset,
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.lo_sizelimit = size == UINT64_MAX ? 0 : size,
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};
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if (ioctl(loop_with_fd, LOOP_SET_STATUS64, &info) < 0)
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return -errno;
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d = new(LoopDevice, 1);
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if (!d)
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return -ENOMEM;
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*d = (LoopDevice) {
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.fd = TAKE_FD(loop_with_fd),
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.node = TAKE_PTR(loopdev),
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.nr = nr,
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};
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*ret = d;
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return 0;
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}
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int loop_device_make_by_path(const char *path, int open_flags, uint32_t loop_flags, LoopDevice **ret) {
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_cleanup_close_ int fd = -1;
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assert(path);
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assert(ret);
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assert(IN_SET(open_flags, O_RDWR, O_RDONLY));
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fd = open(path, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|open_flags);
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if (fd < 0)
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return -errno;
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return loop_device_make(fd, open_flags, 0, 0, loop_flags, ret);
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}
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LoopDevice* loop_device_unref(LoopDevice *d) {
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if (!d)
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return NULL;
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if (d->fd >= 0) {
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if (d->nr >= 0 && !d->relinquished) {
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if (ioctl(d->fd, LOOP_CLR_FD) < 0)
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log_debug_errno(errno, "Failed to clear loop device: %m");
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}
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safe_close(d->fd);
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}
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if (d->nr >= 0 && !d->relinquished) {
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_cleanup_close_ int control = -1;
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control = open("/dev/loop-control", O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
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if (control < 0)
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log_warning_errno(errno,
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"Failed to open loop control device, cannot remove loop device %s: %m",
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strna(d->node));
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else
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for (unsigned n_attempts = 0;;) {
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if (ioctl(control, LOOP_CTL_REMOVE, d->nr) >= 0)
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break;
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if (errno != EBUSY || ++n_attempts >= 64) {
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log_warning_errno(errno, "Failed to remove device %s: %m", strna(d->node));
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break;
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}
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usleep(50 * USEC_PER_MSEC);
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}
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}
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free(d->node);
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return mfree(d);
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}
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void loop_device_relinquish(LoopDevice *d) {
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assert(d);
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/* Don't attempt to clean up the loop device anymore from this point on. Leave the clean-ing up to the kernel
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* itself, using the loop device "auto-clear" logic we already turned on when creating the device. */
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d->relinquished = true;
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}
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int loop_device_open(const char *loop_path, int open_flags, LoopDevice **ret) {
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_cleanup_close_ int loop_fd = -1;
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_cleanup_free_ char *p = NULL;
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struct loop_info64 info;
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struct stat st;
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LoopDevice *d;
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int nr;
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assert(loop_path);
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assert(ret);
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loop_fd = open(loop_path, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|open_flags);
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if (loop_fd < 0)
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return -errno;
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if (fstat(loop_fd, &st) < 0)
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return -errno;
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if (!S_ISBLK(st.st_mode))
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return -ENOTBLK;
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if (ioctl(loop_fd, LOOP_GET_STATUS64, &info) >= 0) {
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#if HAVE_VALGRIND_MEMCHECK_H
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/* Valgrind currently doesn't know LOOP_GET_STATUS64. Remove this once it does */
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VALGRIND_MAKE_MEM_DEFINED(&info, sizeof(info));
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#endif
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nr = info.lo_number;
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} else
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nr = -1;
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p = strdup(loop_path);
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if (!p)
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return -ENOMEM;
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d = new(LoopDevice, 1);
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if (!d)
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return -ENOMEM;
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*d = (LoopDevice) {
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.fd = TAKE_FD(loop_fd),
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.nr = nr,
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.node = TAKE_PTR(p),
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.relinquished = true, /* It's not ours, don't try to destroy it when this object is freed */
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};
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*ret = d;
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return d->fd;
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}
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static int resize_partition(int partition_fd, uint64_t offset, uint64_t size) {
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char sysfs[STRLEN("/sys/dev/block/:/partition") + 2*DECIMAL_STR_MAX(dev_t) + 1];
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_cleanup_free_ char *whole = NULL, *buffer = NULL;
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uint64_t current_offset, current_size, partno;
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_cleanup_close_ int whole_fd = -1;
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struct stat st;
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dev_t devno;
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int r;
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assert(partition_fd >= 0);
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/* Resizes the partition the loopback device refer to (assuming it refers to one instead of an actual
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* loopback device), and changes the offset, if needed. This is a fancy wrapper around
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* BLKPG_RESIZE_PARTITION. */
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if (fstat(partition_fd, &st) < 0)
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return -errno;
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assert(S_ISBLK(st.st_mode));
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xsprintf(sysfs, "/sys/dev/block/%u:%u/partition", major(st.st_rdev), minor(st.st_rdev));
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r = read_one_line_file(sysfs, &buffer);
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if (r == -ENOENT) /* not a partition, cannot resize */
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return -ENOTTY;
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if (r < 0)
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return r;
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r = safe_atou64(buffer, &partno);
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if (r < 0)
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return r;
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xsprintf(sysfs, "/sys/dev/block/%u:%u/start", major(st.st_rdev), minor(st.st_rdev));
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buffer = mfree(buffer);
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r = read_one_line_file(sysfs, &buffer);
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if (r < 0)
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return r;
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r = safe_atou64(buffer, ¤t_offset);
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if (r < 0)
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return r;
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if (current_offset > UINT64_MAX/512U)
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return -EINVAL;
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current_offset *= 512U;
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if (ioctl(partition_fd, BLKGETSIZE64, ¤t_size) < 0)
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return -EINVAL;
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if (size == UINT64_MAX && offset == UINT64_MAX)
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return 0;
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if (current_size == size && current_offset == offset)
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return 0;
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xsprintf(sysfs, "/sys/dev/block/%u:%u/../dev", major(st.st_rdev), minor(st.st_rdev));
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buffer = mfree(buffer);
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r = read_one_line_file(sysfs, &buffer);
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if (r < 0)
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return r;
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r = parse_dev(buffer, &devno);
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if (r < 0)
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return r;
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r = device_path_make_major_minor(S_IFBLK, devno, &whole);
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if (r < 0)
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return r;
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whole_fd = open(whole, O_RDWR|O_CLOEXEC|O_NONBLOCK|O_NOCTTY);
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if (whole_fd < 0)
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return -errno;
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struct blkpg_partition bp = {
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.pno = partno,
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.start = offset == UINT64_MAX ? current_offset : offset,
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.length = size == UINT64_MAX ? current_size : size,
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};
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struct blkpg_ioctl_arg ba = {
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.op = BLKPG_RESIZE_PARTITION,
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.data = &bp,
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.datalen = sizeof(bp),
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};
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if (ioctl(whole_fd, BLKPG, &ba) < 0)
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return -errno;
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return 0;
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}
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int loop_device_refresh_size(LoopDevice *d, uint64_t offset, uint64_t size) {
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struct loop_info64 info;
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assert(d);
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/* Changes the offset/start of the loop device relative to the beginning of the underlying file or
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* block device. If this loop device actually refers to a partition and not a loopback device, we'll
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* try to adjust the partition offsets instead.
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*
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* If either offset or size is UINT64_MAX we won't change that parameter. */
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if (d->fd < 0)
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return -EBADF;
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if (d->nr < 0) /* not a loopback device */
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return resize_partition(d->fd, offset, size);
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if (ioctl(d->fd, LOOP_GET_STATUS64, &info) < 0)
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return -errno;
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#if HAVE_VALGRIND_MEMCHECK_H
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/* Valgrind currently doesn't know LOOP_GET_STATUS64. Remove this once it does */
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VALGRIND_MAKE_MEM_DEFINED(&info, sizeof(info));
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#endif
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if (size == UINT64_MAX && offset == UINT64_MAX)
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return 0;
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if (info.lo_sizelimit == size && info.lo_offset == offset)
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return 0;
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if (size != UINT64_MAX)
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info.lo_sizelimit = size;
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if (offset != UINT64_MAX)
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info.lo_offset = offset;
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if (ioctl(d->fd, LOOP_SET_STATUS64, &info) < 0)
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return -errno;
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return 0;
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}
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int loop_device_flock(LoopDevice *d, int operation) {
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assert(d);
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if (d->fd < 0)
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return -EBADF;
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if (flock(d->fd, operation) < 0)
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return -errno;
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return 0;
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}
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