Btrfs: update total_bytes_pinned when pinning down extents

The extents marked in pin_down_extent() will be unpinned later in
unpin_extent_range(), which decrements total_bytes_pinned.
pin_down_extent() must increment the counter to avoid underflowing it.
Also adjust btrfs_free_tree_block() to avoid accounting for the same
extent twice.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent-tree.c

@@ -6358,6 +6358,7 @@ static int pin_down_extent(struct btrfs_fs_info *fs_info,
 
 	trace_btrfs_space_reservation(fs_info, "pinned",
 				      cache->space_info->flags, num_bytes, 1);
+	percpu_counter_add(&cache->space_info->total_bytes_pinned, num_bytes);
 	set_extent_dirty(fs_info->pinned_extents, bytenr,
 			 bytenr + num_bytes - 1, GFP_NOFS | __GFP_NOFAIL);
 	return 0;
@@ -7204,6 +7205,7 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
 				goto out;
 		}
 
+		pin = 0;
 		cache = btrfs_lookup_block_group(fs_info, buf->start);
 
 		if (btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
@@ -7219,7 +7221,6 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
 		btrfs_free_reserved_bytes(cache, buf->len, 0);
 		btrfs_put_block_group(cache);
 		trace_btrfs_reserved_extent_free(fs_info, buf->start, buf->len);
-		pin = 0;
 	}
 out:
 	if (pin)