btrfs: constify remaining structs with function pointers

* struct extent_io_ops
* struct btrfs_free_space_op
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/free-space-cache.c

@@ -2016,7 +2016,7 @@ static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
 	return true;
 }
 
-static struct btrfs_free_space_op free_space_op = {
+static const struct btrfs_free_space_op free_space_op = {
 	.recalc_thresholds	= recalculate_thresholds,
 	.use_bitmap		= use_bitmap,
 };

fs/btrfs/free-space-cache.h

@@ -37,7 +37,7 @@ struct btrfs_free_space_ctl {
 	int total_bitmaps;
 	int unit;
 	u64 start;
-	struct btrfs_free_space_op *op;
+	const struct btrfs_free_space_op *op;
 	void *private;
 	struct mutex cache_writeout_mutex;
 	struct list_head trimming_ranges;

fs/btrfs/inode-map.c

@@ -334,7 +334,7 @@ static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
 	return true;
 }
 
-static struct btrfs_free_space_op free_ino_op = {
+static const struct btrfs_free_space_op free_ino_op = {
 	.recalc_thresholds	= recalculate_thresholds,
 	.use_bitmap		= use_bitmap,
 };
@@ -356,7 +356,7 @@ static bool pinned_use_bitmap(struct btrfs_free_space_ctl *ctl,
 	return false;
 }
 
-static struct btrfs_free_space_op pinned_free_ino_op = {
+static const struct btrfs_free_space_op pinned_free_ino_op = {
 	.recalc_thresholds	= pinned_recalc_thresholds,
 	.use_bitmap		= pinned_use_bitmap,
 };

fs/btrfs/inode.c

@@ -74,7 +74,7 @@ static const struct inode_operations btrfs_file_inode_operations;
 static const struct address_space_operations btrfs_aops;
 static const struct address_space_operations btrfs_symlink_aops;
 static const struct file_operations btrfs_dir_file_operations;
-static struct extent_io_ops btrfs_extent_io_ops;
+static const struct extent_io_ops btrfs_extent_io_ops;
 
 static struct kmem_cache *btrfs_inode_cachep;
 struct kmem_cache *btrfs_trans_handle_cachep;
@@ -10020,7 +10020,7 @@ static const struct file_operations btrfs_dir_file_operations = {
 	.fsync		= btrfs_sync_file,
 };
 
-static struct extent_io_ops btrfs_extent_io_ops = {
+static const struct extent_io_ops btrfs_extent_io_ops = {
 	.fill_delalloc = run_delalloc_range,
 	.submit_bio_hook = btrfs_submit_bio_hook,
 	.merge_bio_hook = btrfs_merge_bio_hook,

fs/btrfs/tests/free-space-tests.c

@@ -445,11 +445,11 @@ test_steal_space_from_bitmap_to_extent(struct btrfs_block_group_cache *cache)
 	int ret;
 	u64 offset;
 	u64 max_extent_size;
-	struct btrfs_free_space_op test_free_space_ops = {
+	const struct btrfs_free_space_op test_free_space_ops = {
 		.recalc_thresholds = cache->free_space_ctl->op->recalc_thresholds,
 		.use_bitmap = test_use_bitmap,
 	};
-	struct btrfs_free_space_op *orig_free_space_ops;
+	const struct btrfs_free_space_op *orig_free_space_ops;
 
 	test_msg("Running space stealing from bitmap to extent\n");