bcachefs: bch2_trigger_alloc() handles state changes better

bch2_trigger_alloc() kicks off certain tasks on bucket state changes;
e.g. triggering the bucket discard worker and the invalidate worker.

We've observed the discard worker running too often - most runs it
doesn't do any work, according to the tracepoint - so clearly, we're
kicking it off too often.

This adds an explicit statechange() macro to make these checks more
precise.

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

diff --git a/fs/bcachefs/alloc_background.c b/fs/bcachefs/alloc_background.c
index fd3e175d83423261d68124cd26fc0351488ad05e..c7be6afe89553b154ff8ba1d2899908026c5451a 100644 (file)
--- a/fs/bcachefs/alloc_background.c
+++ b/fs/bcachefs/alloc_background.c
@@ -860,23 +860,28 @@ int bch2_trigger_alloc(struct btree_trans *trans,
                        *bucket_gen(ca, new.k->p.offset) = new_a->gen;
 
                bch2_dev_usage_update(c, ca, old_a, new_a, journal_seq, false);
+               percpu_up_read(&c->mark_lock);
+
+#define eval_state(_a, expr)           ({ const struct bch_alloc_v4 *a = _a; expr; })
+#define statechange(expr)              !eval_state(old_a, expr) && eval_state(new_a, expr)
+#define bucket_flushed(a)              (!a->journal_seq || a->journal_seq <= c->journal.flushed_seq_ondisk)
 
-               if (new_a->data_type == BCH_DATA_free &&
-                   (!new_a->journal_seq || new_a->journal_seq < c->journal.flushed_seq_ondisk))
+               if (statechange(a->data_type == BCH_DATA_free &&
+                               bucket_flushed(a)))
                        closure_wake_up(&c->freelist_wait);
 
-               if (new_a->data_type == BCH_DATA_need_discard &&
-                   (!bucket_journal_seq || bucket_journal_seq < c->journal.flushed_seq_ondisk))
+               if (statechange(a->data_type == BCH_DATA_need_discard &&
+                               bucket_flushed(a)) &&
+                   !bch2_bucket_is_open(c, new.k->p.inode, new.k->p.offset))
                        bch2_do_discards(c);
 
-               if (old_a->data_type != BCH_DATA_cached &&
-                   new_a->data_type == BCH_DATA_cached &&
+               if (statechange(a->data_type == BCH_DATA_cached) &&
+                   !bch2_bucket_is_open(c, new.k->p.inode, new.k->p.offset) &&
                    should_invalidate_buckets(ca, bch2_dev_usage_read(ca)))
                        bch2_do_invalidates(c);
 
-               if (new_a->data_type == BCH_DATA_need_gc_gens)
+               if (statechange(a->data_type == BCH_DATA_need_gc_gens))
                        bch2_do_gc_gens(c);
-               percpu_up_read(&c->mark_lock);
        }
 
        if ((flags & BTREE_TRIGGER_GC) &&