bcachefs: Separate discards from rest of journal reclaim

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/journal.c

@@ -322,6 +322,7 @@ static int __journal_res_get(struct journal *j, struct journal_res *res,
 {
 	struct bch_fs *c = container_of(j, struct bch_fs, journal);
 	struct journal_buf *buf;
+	bool can_discard;
 	int ret;
 retry:
 	if (journal_res_get_fast(j, res, flags))
@@ -370,18 +371,28 @@ static int __journal_res_get(struct journal *j, struct journal_res *res,
 	    !j->res_get_blocked_start)
 		j->res_get_blocked_start = local_clock() ?: 1;
 
+	can_discard = j->can_discard;
 	spin_unlock(&j->lock);
 
 	if (!ret)
 		goto retry;
+
 	if (ret == -ENOSPC) {
 		/*
 		 * Journal is full - can't rely on reclaim from work item due to
 		 * freezing:
 		 */
 		trace_journal_full(c);
-		if (!(flags & JOURNAL_RES_GET_NONBLOCK))
+
+		if (!(flags & JOURNAL_RES_GET_NONBLOCK)) {
+			if (can_discard) {
+				bch2_journal_do_discards(j);
+				goto retry;
+			}
+
 			bch2_journal_reclaim_work(&j->reclaim_work.work);
+		}
+
 		ret = -EAGAIN;
 	}
 

fs/bcachefs/journal_reclaim.c

@@ -45,6 +45,7 @@ void bch2_journal_space_available(struct journal *j)
 	unsigned unwritten_sectors = j->reservations.prev_buf_unwritten
 		? journal_prev_buf(j)->sectors
 		: 0;
+	bool can_discard = false;
 	int ret = 0;
 
 	lockdep_assert_held(&j->lock);
@@ -65,9 +66,14 @@ void bch2_journal_space_available(struct journal *j)
 		       ja->bucket_seq[ja->dirty_idx_ondisk] < j->last_seq_ondisk)
 			ja->dirty_idx_ondisk = (ja->dirty_idx_ondisk + 1) % ja->nr;
 
+		if (ja->discard_idx != ja->dirty_idx_ondisk)
+			can_discard = true;
+
 		nr_online++;
 	}
 
+	j->can_discard = can_discard;
+
 	if (nr_online < c->opts.metadata_replicas_required) {
 		ret = -EROFS;
 		sectors_next_entry = 0;
@@ -156,7 +162,7 @@ static bool should_discard_bucket(struct journal *j, struct journal_device *ja)
  * Advance ja->discard_idx as long as it points to buckets that are no longer
  * dirty, issuing discards if necessary:
  */
-static void bch2_journal_do_discards(struct journal *j)
+void bch2_journal_do_discards(struct journal *j)
 {
 	struct bch_fs *c = container_of(j, struct bch_fs, journal);
 	struct bch_dev *ca;

fs/bcachefs/journal_reclaim.h

@@ -34,6 +34,7 @@ void bch2_journal_pin_add_if_older(struct journal *,
 				  journal_pin_flush_fn);
 void bch2_journal_pin_flush(struct journal *, struct journal_entry_pin *);
 
+void bch2_journal_do_discards(struct journal *);
 void bch2_journal_reclaim_work(struct work_struct *);
 
 void bch2_journal_flush_pins(struct journal *, u64);

fs/bcachefs/journal_types.h

@@ -210,6 +210,8 @@ struct journal {
 
 	/* protects advancing ja->discard_idx: */
 	struct mutex		discard_lock;
+	bool			can_discard;
+
 	unsigned		write_delay_ms;
 	unsigned		reclaim_delay_ms;