nilfs2: refactor nilfs_segctor_thread()

Simplify nilfs_segctor_thread(), the main loop function of the log writer
thread, to make the basic structure easier to understand.

In particular, the acquisition and release of the sc_state_lock spinlock
was scattered throughout the function, so extract the determination of
whether log writing is required into a helper function and make the
spinlock lock sections clearer.

Link: https://lkml.kernel.org/r/20240826174116.5008-9-konishi.ryusuke@gmail.com
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Huang Xiaojia <huangxiaojia2@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/nilfs2/segment.c

@@ -2627,6 +2627,32 @@ static int nilfs_segctor_flush_mode(struct nilfs_sc_info *sci)
 	return SC_LSEG_SR;
 }
 
+/**
+ * nilfs_log_write_required - determine whether log writing is required
+ * @sci:   nilfs_sc_info struct
+ * @modep: location for storing log writing mode
+ *
+ * Return: true if log writing is required, false otherwise.  If log writing
+ * is required, the mode is stored in the location pointed to by @modep.
+ */
+static bool nilfs_log_write_required(struct nilfs_sc_info *sci, int *modep)
+{
+	bool timedout, ret = true;
+
+	spin_lock(&sci->sc_state_lock);
+	timedout = ((sci->sc_state & NILFS_SEGCTOR_COMMIT) &&
+		   time_after_eq(jiffies, sci->sc_timer.expires));
+	if (timedout || sci->sc_seq_request != sci->sc_seq_done)
+		*modep = SC_LSEG_SR;
+	else if (sci->sc_flush_request)
+		*modep = nilfs_segctor_flush_mode(sci);
+	else
+		ret = false;
+
+	spin_unlock(&sci->sc_state_lock);
+	return ret;
+}
+
 /**
  * nilfs_segctor_thread - main loop of the log writer thread
  * @arg: pointer to a struct nilfs_sc_info.
@@ -2642,70 +2668,39 @@ static int nilfs_segctor_thread(void *arg)
 {
 	struct nilfs_sc_info *sci = (struct nilfs_sc_info *)arg;
 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
-	int timeout = 0;
 
 	nilfs_info(sci->sc_super,
 		   "segctord starting. Construction interval = %lu seconds, CP frequency < %lu seconds",
 		   sci->sc_interval / HZ, sci->sc_mjcp_freq / HZ);
 
 	set_freezable();
-	spin_lock(&sci->sc_state_lock);
+
- loop:
+	while (!kthread_should_stop()) {
-	for (;;) {
+		DEFINE_WAIT(wait);
+		bool should_write;
 		int mode;
 
-		if (kthread_should_stop())
+		if (freezing(current)) {
-			goto end_thread;
+			try_to_freeze();
-
+			continue;
-		if (timeout || sci->sc_seq_request != sci->sc_seq_done)
+		}
-			mode = SC_LSEG_SR;
-		else if (sci->sc_flush_request)
-			mode = nilfs_segctor_flush_mode(sci);
-		else
-			break;
-
-		spin_unlock(&sci->sc_state_lock);
-		nilfs_segctor_thread_construct(sci, mode);
-		spin_lock(&sci->sc_state_lock);
-		timeout = 0;
-	}
-
-
-	if (freezing(current)) {
-		spin_unlock(&sci->sc_state_lock);
-		try_to_freeze();
-		spin_lock(&sci->sc_state_lock);
-	} else {
-		DEFINE_WAIT(wait);
-		int should_sleep = 1;
 
 		prepare_to_wait(&sci->sc_wait_daemon, &wait,
 				TASK_INTERRUPTIBLE);
-
+		should_write = nilfs_log_write_required(sci, &mode);
-		if (sci->sc_seq_request != sci->sc_seq_done)
+		if (!should_write)
-			should_sleep = 0;
-		else if (sci->sc_flush_request)
-			should_sleep = 0;
-		else if (sci->sc_state & NILFS_SEGCTOR_COMMIT)
-			should_sleep = time_before(jiffies,
-					sci->sc_timer.expires);
-
-		if (should_sleep) {
-			spin_unlock(&sci->sc_state_lock);
 			schedule();
-			spin_lock(&sci->sc_state_lock);
-		}
 		finish_wait(&sci->sc_wait_daemon, &wait);
-		timeout = ((sci->sc_state & NILFS_SEGCTOR_COMMIT) &&
-			   time_after_eq(jiffies, sci->sc_timer.expires));
 
 		if (nilfs_sb_dirty(nilfs) && nilfs_sb_need_update(nilfs))
 			set_nilfs_discontinued(nilfs);
-	}
-	goto loop;
 
- end_thread:
+		if (should_write)
+			nilfs_segctor_thread_construct(sci, mode);
+	}
+
 	/* end sync. */
+	spin_lock(&sci->sc_state_lock);
 	sci->sc_task = NULL;
 	timer_shutdown_sync(&sci->sc_timer);
 	spin_unlock(&sci->sc_state_lock);