reread-partition-table: trigger change events when we failed to lock device

Before aa47d8ade18cc4a079fef5a1aaa37d763507104e, when we failed to lock
the device node, we simply trigger change events for the device and its
partitions. But the commit killed the fallback logic. Let's restore that.

Fixes #39544.

src/login/logind-session.c

@@ -423,6 +423,8 @@ static int session_load_leader(Session *s, uint64_t pidfdid) {
                 return 0;
 
         r = pidref_set_pid(&pidref, s->deserialized_pid);
+        if (r == -ESRCH)
+                return log_warning_errno(r, "Leader of session '%s' is gone while deserializing.", s->id);
         if (r < 0)
                 return log_error_errno(r, "Failed to deserialize leader PID for session '%s': %m", s->id);
         if (pidref.fd < 0)
@@ -437,9 +439,9 @@ static int session_load_leader(Session *s, uint64_t pidfdid) {
                                                pidref.pid);
 
                 if (pidref.fd_id != pidfdid)
-                        return log_error_errno(SYNTHETIC_ERRNO(ESRCH),
-                                               "Deserialized pidfd id for process " PID_FMT " (%" PRIu64 ") doesn't match with the current one (%" PRIu64 "), refusing.",
-                                               pidref.pid, pidfdid, pidref.fd_id);
+                        return log_warning_errno(SYNTHETIC_ERRNO(ESRCH),
+                                                 "Deserialized pidfd id for process " PID_FMT " (%" PRIu64 ") doesn't match the current one (%" PRIu64 "). PID recycled while deserializing?",
+                                                 pidref.pid, pidfdid, pidref.fd_id);
         }
 
         r = session_set_leader_consume(s, TAKE_PIDREF(pidref));

src/login/logind.c

@@ -441,13 +441,13 @@ static int deliver_session_device_fd(Session *s, const char *fdname, int fd, dev
         return 0;
 }
 
-static int deliver_session_leader_fd_consume(Session *s, const char *fdname, int fd) {
+static int deliver_session_leader_fd_consume(Session *s, const char *fdname, int fd_consume) {
+        _cleanup_close_ int fd = ASSERT_FD(fd_consume);
         _cleanup_(pidref_done) PidRef leader_fdstore = PIDREF_NULL;
         int r;
 
         assert(s);
         assert(fdname);
-        assert(fd >= 0);
 
         /* Already deserialized via pidfd id? */
         if (pidref_is_set(&s->leader)) {
@@ -473,12 +473,13 @@ static int deliver_session_leader_fd_consume(Session *s, const char *fdname, int
 
         r = pidref_set_pidfd_take(&leader_fdstore, fd);
         if (r < 0) {
-                if (r == -ESRCH)
-                        log_debug_errno(r, "Leader of session '%s' is gone while deserializing.", s->id);
-                else
-                        log_warning_errno(r, "Failed to create reference to leader of session '%s': %m", s->id);
+                log_warning_errno(r,
+                                  r == -ESRCH ? "Leader of session '%s' is gone while deserializing."
+                                              : "Failed to create reference to leader of session '%s': %m",
+                                  s->id);
                 goto fail_close;
         }
+        TAKE_FD(fd);
 
         if (leader_fdstore.pid != s->deserialized_pid)
                 log_warning("Leader from pidfd (" PID_FMT ") doesn't match with LEADER=" PID_FMT " for session '%s', proceeding anyway.",
@@ -491,7 +492,7 @@ static int deliver_session_leader_fd_consume(Session *s, const char *fdname, int
         return 0;
 
 fail_close:
-        close_and_notify_warn(fd, fdname);
+        close_and_notify_warn(TAKE_FD(fd), fdname);
         return r;
 }
 
@@ -565,7 +566,7 @@ static int manager_enumerate_sessions(Manager *m) {
                 session_add_to_gc_queue(s);
 
                 k = session_load(s);
-                if (k < 0)
+                if (k < 0 && k != -ESRCH)
                         RET_GATHER(r, log_warning_errno(k, "Failed to deserialize session '%s', ignoring: %m", s->id));
         }
 

src/shared/reread-partition-table.c

@@ -259,8 +259,16 @@ static int reread_partition_table_full(sd_device *dev, int fd, RereadPartitionTa
                 if (lock_fd < 0)
                         return log_device_debug_errno(dev, lock_fd, "Failed top open lock fd for block device '%s': %m", p);
 
-                if (flock(lock_fd, LOCK_EX|LOCK_NB) < 0)
-                        return log_device_debug_errno(dev, errno, "Failed to take BSD lock on block device '%s': %m", p);
+                if (flock(lock_fd, LOCK_EX|LOCK_NB) < 0) {
+                        r = log_device_debug_errno(dev, errno, "Failed to take BSD lock on block device '%s': %m", p);
+
+                        if (r == -EBUSY && FLAGS_SET(flags, REREADPT_FORCE_UEVENT)) {
+                                log_device_debug(dev, "Giving up rereading partition table of '%s'. Triggering change events for the device and its partitions.", p);
+                                (void) trigger_partitions(dev, /* blkrrpart_success= */ false);
+                        }
+
+                        return r;
+                }
         }
 
         r = blockdev_partscan_enabled(dev);