bcachefs: Fix for an assertion on filesystem error

Normally the in memory i_size is always greater than or equal to i_size
on disk; this doesn't hold on filesystem error.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/fs-io.c

@@ -2255,6 +2255,15 @@ int bch2_truncate(struct bch_inode_info *inode, struct iattr *iattr)
 	ret = PTR_ERR_OR_ZERO(iter);
 	bch2_trans_exit(&trans);
 
+	if (ret)
+		goto err;
+
+	/*
+	 * check this before next assertion; on filesystem error our normal
+	 * invariants are a bit broken (truncate has to truncate the page cache
+	 * before the inode).
+	 */
+	ret = bch2_journal_error(&c->journal);
 	if (ret)
 		goto err;