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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/***
Copyright © 2010 ProFUSION embedded systems
***/
#include <linux/loop.h>
#include <sys/ioctl.h>
#include <unistd.h>
#if HAVE_VALGRIND_MEMCHECK_H
#include <valgrind/memcheck.h>
#endif
#include "sd-device.h"
#include "alloc-util.h"
#include "blockdev-util.h"
#include "detach-loopback.h"
#include "device-util.h"
#include "fd-util.h"
typedef struct LoopbackDevice {
char *path;
dev_t devnum;
LIST_FIELDS(struct LoopbackDevice, loopback_device);
} LoopbackDevice;
static void loopback_device_free(LoopbackDevice **head, LoopbackDevice *m) {
assert(head);
assert(m);
LIST_REMOVE(loopback_device, *head, m);
free(m->path);
free(m);
}
static void loopback_device_list_free(LoopbackDevice **head) {
assert(head);
while (*head)
loopback_device_free(head, *head);
}
static int loopback_list_get(LoopbackDevice **head) {
_cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
int r;
assert(head);
r = sd_device_enumerator_new(&e);
if (r < 0)
return r;
r = sd_device_enumerator_allow_uninitialized(e);
if (r < 0)
return r;
r = sd_device_enumerator_add_match_subsystem(e, "block", true);
if (r < 0)
return r;
r = sd_device_enumerator_add_match_sysname(e, "loop*");
if (r < 0)
return r;
r = sd_device_enumerator_add_match_sysattr(e, "loop/backing_file", NULL, true);
if (r < 0)
return r;
FOREACH_DEVICE(e, d) {
_cleanup_free_ char *p = NULL;
const char *dn;
LoopbackDevice *lb;
dev_t devnum;
if (sd_device_get_devnum(d, &devnum) < 0 ||
sd_device_get_devname(d, &dn) < 0)
continue;
p = strdup(dn);
if (!p)
return -ENOMEM;
lb = new(LoopbackDevice, 1);
if (!lb)
return -ENOMEM;
*lb = (LoopbackDevice) {
.path = TAKE_PTR(p),
.devnum = devnum,
};
LIST_PREPEND(loopback_device, *head, lb);
}
return 0;
}
static int delete_loopback(const char *device) {
_cleanup_close_ int fd = -EBADF;
struct loop_info64 info;
assert(device);
fd = open(device, O_RDONLY|O_CLOEXEC);
if (fd < 0) {
log_debug_errno(errno, "Failed to open loopback device %s: %m", device);
return errno == ENOENT ? 0 : -errno;
}
/* Loopback block devices don't sync in-flight blocks when we clear the fd, hence sync explicitly
* first */
if (fsync(fd) < 0)
log_debug_errno(errno, "Failed to sync loop block device %s, ignoring: %m", device);
if (ioctl(fd, LOOP_CLR_FD, 0) < 0) {
if (errno == ENXIO) /* Nothing bound, didn't do anything */
return 0;
if (errno != EBUSY)
return log_debug_errno(errno, "Failed to clear loopback device %s: %m", device);
if (ioctl(fd, LOOP_GET_STATUS64, &info) < 0) {
if (errno == ENXIO) /* What? Suddenly detached after all? That's fine by us then. */
return 1;
log_debug_errno(errno, "Failed to invoke LOOP_GET_STATUS64 on loopback device %s, ignoring: %m", device);
return -EBUSY; /* propagate original error */
}
#if HAVE_VALGRIND_MEMCHECK_H
VALGRIND_MAKE_MEM_DEFINED(&info, sizeof(info));
#endif
if (FLAGS_SET(info.lo_flags, LO_FLAGS_AUTOCLEAR)) /* someone else already set LO_FLAGS_AUTOCLEAR for us? fine by us */
return -EBUSY; /* propagate original error */
info.lo_flags |= LO_FLAGS_AUTOCLEAR;
if (ioctl(fd, LOOP_SET_STATUS64, &info) < 0) {
if (errno == ENXIO) /* Suddenly detached after all? Fine by us */
return 1;
log_debug_errno(errno, "Failed to set LO_FLAGS_AUTOCLEAR flag for loop device %s, ignoring: %m", device);
} else
log_debug("Successfully set LO_FLAGS_AUTOCLEAR flag for loop device %s.", device);
return -EBUSY;
}
if (ioctl(fd, LOOP_GET_STATUS64, &info) < 0) {
/* If the LOOP_CLR_FD above succeeded we'll see ENXIO here. */
if (errno == ENXIO)
log_debug("Successfully detached loopback device %s.", device);
else
log_debug_errno(errno, "Failed to invoke LOOP_GET_STATUS64 on loopback device %s, ignoring: %m", device); /* the LOOP_CLR_FD at least worked, let's hope for the best */
return 1;
}
#if HAVE_VALGRIND_MEMCHECK_H
VALGRIND_MAKE_MEM_DEFINED(&info, sizeof(info));
#endif
/* Linux makes LOOP_CLR_FD succeed whenever LO_FLAGS_AUTOCLEAR is set without actually doing
* anything. Very confusing. Let's hence not claim we did anything in this case. */
if (FLAGS_SET(info.lo_flags, LO_FLAGS_AUTOCLEAR))
log_debug("Successfully called LOOP_CLR_FD on a loopback device %s with autoclear set, which is a NOP.", device);
else
log_debug("Weird, LOOP_CLR_FD succeeded but the device is still attached on %s.", device);
return -EBUSY; /* Nothing changed, the device is still attached, hence it apparently is still busy */
}
static int loopback_points_list_detach(LoopbackDevice **head, bool *changed, bool last_try) {
int n_failed = 0, r;
dev_t rootdev = 0, usrdev = 0;
assert(head);
assert(changed);
(void) get_block_device_harder("/", &rootdev);
(void) block_get_whole_disk(rootdev, &rootdev);
(void) get_block_device_harder("/usr", &usrdev);
(void) block_get_whole_disk(usrdev, &usrdev);
LIST_FOREACH(loopback_device, m, *head) {
if ((major(rootdev) != 0 && rootdev == m->devnum) ||
(major(usrdev) != 0 && usrdev == m->devnum)) {
log_debug("Not detaching loopback device %s that backs the OS itself, skipping.", m->path);
n_failed++;
continue;
}
log_info("Detaching loopback %s.", m->path);
r = delete_loopback(m->path);
if (r < 0) {
log_full_errno(last_try ? LOG_ERR : LOG_INFO, r, "Could not detach loopback %s: %m", m->path);
n_failed++;
continue;
}
if (r > 0)
*changed = true;
loopback_device_free(head, m);
}
return n_failed;
}
int loopback_detach_all(bool *changed, bool last_try) {
_cleanup_(loopback_device_list_free) LIST_HEAD(LoopbackDevice, loopback_list_head);
int r;
assert(changed);
LIST_HEAD_INIT(loopback_list_head);
r = loopback_list_get(&loopback_list_head);
if (r < 0)
return r;
return loopback_points_list_detach(&loopback_list_head, changed, last_try);
}
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