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-rw-r--r--src/shutdown/detach-loopback.c225
1 files changed, 225 insertions, 0 deletions
diff --git a/src/shutdown/detach-loopback.c b/src/shutdown/detach-loopback.c
new file mode 100644
index 0000000..267509f
--- /dev/null
+++ b/src/shutdown/detach-loopback.c
@@ -0,0 +1,225 @@
+/* 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);
+}