bcachefs: bch2_journal_halt() now takes journal lock

This change is prep work for moving some work from
__journal_entry_close() to journal_entry_open(): without this change,
journal_entry_open() doesn't know if it's going to be able to open a new
journal entry until the cmpxchg loop, meaning it can't create the new
journal pin entry and update other global state because those have to be
done prior to the cmpxchg opening the new journal entry.

Fortunately, we don't call bch2_journal_halt() from interrupt context.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/journal.c

@@ -96,12 +96,15 @@ static void bch2_journal_buf_init(struct journal *j)
 void bch2_journal_halt(struct journal *j)
 {
 	union journal_res_state old, new;
-	u64 v = atomic64_read(&j->reservations.counter);
+	u64 v;
+
+	spin_lock(&j->lock);
 
+	v = atomic64_read(&j->reservations.counter);
 	do {
 		old.v = new.v = v;
 		if (old.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL)
-			return;
+			goto out;
 
 		new.cur_entry_offset = JOURNAL_ENTRY_ERROR_VAL;
 	} while ((v = atomic64_cmpxchg(&j->reservations.counter,
@@ -115,6 +118,8 @@ void bch2_journal_halt(struct journal *j)
 		j->err_seq = journal_cur_seq(j);
 	journal_wake(j);
 	closure_wake_up(&journal_cur_buf(j)->wait);
+out:
+	spin_unlock(&j->lock);
 }
 
 /* journal entry close/open: */
@@ -266,6 +271,9 @@ static int journal_entry_open(struct journal *j)
 	if (j->cur_entry_error)
 		return j->cur_entry_error;
 
+	if (bch2_journal_error(j))
+		return cur_entry_insufficient_devices; /* -EROFS */
+
 	BUG_ON(!j->cur_entry_sectors);
 
 	/* We used to add things to the first journal entry before opening it,
@@ -296,8 +304,7 @@ static int journal_entry_open(struct journal *j)
 	do {
 		old.v = new.v = v;
 
-		if (old.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL)
-			return cur_entry_insufficient_devices;
+		BUG_ON(old.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL);
 
 		EBUG_ON(journal_state_count(new, new.idx));
 		journal_state_inc(&new);