btrfs: always update fstrim_range on failure in FITRIM ioctl

Even in case of failure we could've discarded some data and userspace
should be made aware of it, so copy fstrim_range to userspace
regardless.

Also make sure to update the trimmed bytes amount even if
btrfs_trim_free_extents fails.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Luca Stefani <luca.stefani.ge1@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: luca020400

fs/btrfs/extent-tree.c

@@ -6551,13 +6551,13 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
 			continue;
 
 		ret = btrfs_trim_free_extents(device, &group_trimmed);
+
+		trimmed += group_trimmed;
 		if (ret) {
 			dev_failed++;
 			dev_ret = ret;
 			break;
 		}
-
-		trimmed += group_trimmed;
 	}
 	mutex_unlock(&fs_devices->device_list_mutex);
 

fs/btrfs/ioctl.c

@@ -543,13 +543,11 @@ static noinline int btrfs_ioctl_fitrim(struct btrfs_fs_info *fs_info,
 
 	range.minlen = max(range.minlen, minlen);
 	ret = btrfs_trim_fs(fs_info, &range);
-	if (ret < 0)
-		return ret;
 
 	if (copy_to_user(arg, &range, sizeof(range)))
 		return -EFAULT;
 
-	return 0;
+	return ret;
 }
 
 int __pure btrfs_is_empty_uuid(const u8 *uuid)