bcachefs: Shutdown path improvements

We're seeing occasional firings of the assertion in the key cache
shutdown code that nr_dirty == 0, which means we must sometimes be doing
transaction commits after we've gone read only.

Cleanups & changes:
 - BCH_FS_ALLOC_CLEAN renamed to BCH_FS_CLEAN_SHUTDOWN
 - new helper bch2_btree_interior_updates_flush(), which returns true if
   it had to wait
 - bch2_btree_flush_writes() now also returns true if there were btree
   writes in flight
 - __bch2_fs_read_only now checks if btree writes were in flight in the
   shutdown loop: btree write completion does a transaction update, to
   update the pointer in the parent node
 - assert that !BCH_FS_CLEAN_SHUTDOWN in __bch2_trans_commit

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

1 files changed, 13 insertions, 5 deletions

diff --git a/fs/bcachefs/btree_update_interior.c b/fs/bcachefs/btree_update_interior.c
index 7a092d852930..27ab1cde2217 100644
--- a/fs/bcachefs/btree_update_interior.c
+++ b/fs/bcachefs/btree_update_interior.c
@@ -2175,19 +2175,27 @@ void bch2_btree_updates_to_text(struct printbuf *out, struct bch_fs *c)
 	mutex_unlock(&c->btree_interior_update_lock);
 }
 
-size_t bch2_btree_interior_updates_nr_pending(struct bch_fs *c)
+static bool bch2_btree_interior_updates_pending(struct bch_fs *c)
 {
-	size_t ret = 0;
-	struct list_head *i;
+	bool ret;
 
 	mutex_lock(&c->btree_interior_update_lock);
-	list_for_each(i, &c->btree_interior_update_list)
-		ret++;
+	ret = !list_empty(&c->btree_interior_update_list);
 	mutex_unlock(&c->btree_interior_update_lock);
 
 	return ret;
 }
 
+bool bch2_btree_interior_updates_flush(struct bch_fs *c)
+{
+	bool ret = bch2_btree_interior_updates_pending(c);
+
+	if (ret)
+		closure_wait_event(&c->btree_interior_update_wait,
+				   !bch2_btree_interior_updates_pending(c));
+	return ret;
+}
+
 void bch2_journal_entries_to_btree_roots(struct bch_fs *c, struct jset *jset)
 {
 	struct btree_root *r;