Re: [PATCH 1/3] btrfs-progs: unify sizeof(struct btrfs_super_block) and BTRFS_SUPER_INFO_SIZE

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2021/10/21 20:40, David Sterba wrote:
> On Thu, Oct 21, 2021 at 09:40:18AM +0800, Qu Wenruo wrote:
>> Just like kernel change, pad struct btrfs_super_block to 4096 bytes.
>>
>> Signed-off-by: Qu Wenruo <wqu@suse.com>
>> ---
>>   kernel-shared/ctree.h   | 7 +++++++
>>   kernel-shared/disk-io.h | 3 ---
>>   2 files changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel-shared/ctree.h b/kernel-shared/ctree.h
>> index 563ea50b3587..6451690ce4fa 100644
>> --- a/kernel-shared/ctree.h
>> +++ b/kernel-shared/ctree.h
>> @@ -406,6 +406,9 @@ struct btrfs_root_backup {
>>   	u8 unused_8[10];
>>   } __attribute__ ((__packed__));
>>
>> +#define BTRFS_SUPER_INFO_OFFSET SZ_64K
>> +#define BTRFS_SUPER_INFO_SIZE 4096
>> +
>>   /*
>>    * the super block basically lists the main trees of the FS
>>    * it currently lacks any block count etc etc
>> @@ -456,8 +459,12 @@ struct btrfs_super_block {
>>   	__le64 reserved[28];
>>   	u8 sys_chunk_array[BTRFS_SYSTEM_CHUNK_ARRAY_SIZE];
>>   	struct btrfs_root_backup super_roots[BTRFS_NUM_BACKUP_ROOTS];
>> +	/* Padded to 4096 bytes */
>> +	u8 padding[565];
>>   } __attribute__ ((__packed__));
>>
>> +static_assert(sizeof(struct btrfs_super_block) == BTRFS_SUPER_INFO_SIZE);
>
> Using static_assert breaks build on musl (you can verify that by running
> ci/ci-build-musl if you have docker installed and set up).
>
> There already is macro BUILD_ASSERT used in ioctl.h, eventually we can
> copy the static_assert from kernel or use _Static_assert directly.
>
Mind to fix that on your side?

As I don't yet have any building environment for musl to verify the
failure or fix.

Thanks,
Qu