bcachefs: Revert "Ensure journal doesn't get stuck in nochanges mode"

This patch was originally to work around the journal geting stuck in
nochanges mode - but that was just a hack, we needed to fix the actual
bug. It should be fixed now, so revert it.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/journal.h

@@ -431,7 +431,6 @@ static inline int bch2_journal_preres_get_fast(struct journal *j,
 		ret = 0;
 
 		if ((flags & JOURNAL_RES_GET_RESERVED) ||
-		    test_bit(JOURNAL_NOCHANGES, &j->flags) ||
 		    new.reserved + d < new.remaining) {
 			new.reserved += d;
 			ret = 1;

fs/bcachefs/journal_io.c

@@ -1616,7 +1616,7 @@ void bch2_journal_write(struct closure *cl)
 
 	w->devs_written = bch2_bkey_devs(bkey_i_to_s_c(&w->key));
 
-	if (test_bit(JOURNAL_NOCHANGES, &j->flags))
+	if (c->opts.nochanges)
 		goto no_io;
 
 	for_each_rw_member(ca, c, i)

fs/bcachefs/journal_reclaim.c

@@ -34,10 +34,8 @@ unsigned bch2_journal_dev_buckets_available(struct journal *j,
 					    struct journal_device *ja,
 					    enum journal_space_from from)
 {
-	unsigned available = !test_bit(JOURNAL_NOCHANGES, &j->flags)
-		? ((journal_space_from(ja, from) -
-		    ja->cur_idx - 1 + ja->nr) % ja->nr)
-		: ja->nr;
+	unsigned available = (journal_space_from(ja, from) -
+			      ja->cur_idx - 1 + ja->nr) % ja->nr;
 
 	/*
 	 * Don't use the last bucket unless writing the new last_seq

fs/bcachefs/journal_types.h

@@ -151,7 +151,6 @@ enum {
 	JOURNAL_NEED_WRITE,
 	JOURNAL_MAY_GET_UNRESERVED,
 	JOURNAL_MAY_SKIP_FLUSH,
-	JOURNAL_NOCHANGES,
 };
 
 /* Embedded in struct bch_fs */

fs/bcachefs/super.c

@@ -835,9 +835,6 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 	if (ret)
 		goto err;
 
-	if (c->opts.nochanges)
-		set_bit(JOURNAL_NOCHANGES, &c->journal.flags);
-
 	mi = bch2_sb_get_members(c->disk_sb.sb);
 	for (i = 0; i < c->sb.nr_devices; i++)
 		if (bch2_dev_exists(c->disk_sb.sb, mi, i) &&