Fix ModelCheckpoint callback for no loggers case (#18867)

Author: ioangatop

src/lightning/pytorch/CHANGELOG.md

@@ -36,6 +36,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed an issue when `BatchSizeFinder` `steps_per_trial` parameter ends up defining how many validation batches to run during the entire training ([#18394](https://github.com/Lightning-AI/lightning/issues/18394))
 
 
+- Fixed an issue saving the `last.ckpt` file when using `ModelCheckpoint` on a remote filesystem and no logger is used ([#18867](https://github.com/Lightning-AI/lightning/issues/18867))
+
 
 ## [2.1.0] - 2023-10-11
 

src/lightning/pytorch/callbacks/model_checkpoint.py

@@ -266,6 +266,7 @@ def setup(self, trainer: "pl.Trainer", pl_module: "pl.LightningModule", stage: s
         dirpath = self.__resolve_ckpt_dir(trainer)
         dirpath = trainer.strategy.broadcast(dirpath)
         self.dirpath = dirpath
+        self._fs = get_filesystem(self.dirpath or "")
         if trainer.is_global_zero and stage == "fit":
             self.__warn_if_dir_not_empty(self.dirpath)