Re: [Y2038] [PATCH 13/16] hfs/hfsplus: use 64-bit inode timestamps

Viacheslav Dubeyko
2019-11-13T17:04:06Z

> On Nov 13, 2019, at 11:06 AM, Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Wed, Nov 13, 2019 at 7:00 AM Viacheslav Dubeyko <slava@dubeyko.com> wrote:
>>> On Nov 9, 2019, at 12:32 AM, Arnd Bergmann <arnd@arndb.de> wrote:
>>> * There are two time systems. Both are based on seconds since
>>> * a particular time/date.
>>> - * Unix: unsigned lil-endian since 00:00 GMT, Jan. 1, 1970
>>> + * Unix: signed little-endian since 00:00 GMT, Jan. 1, 1970
>>> * mac: unsigned big-endian since 00:00 GMT, Jan. 1, 1904
>>> *
>>> + * HFS implementations are highly inconsistent, this one matches the
>>> + * traditional behavior of 64-bit Linux, giving the most useful
>>> + * time range between 1970 and 2106, by treating any on-disk timestamp
>>> + * under 2082844800U (Jan 1 1970) as a time between 2040 and 2106.
>>> */
>>> -#define __hfs_u_to_mtime(sec) cpu_to_be32(sec + 2082844800U - sys_tz.tz_minuteswest * 60)
>>> -#define __hfs_m_to_utime(sec) (be32_to_cpu(sec) - 2082844800U + sys_tz.tz_minuteswest * 60)
>>
>> I believe it makes sense to introduce some constant instead of hardcoded value (2082844800U and 60).
>> It will be easier to understand the code without necessity to take a look into the comments.
>> What do you think?
>
> Every other user of sys_tz.tz_minuteswest uses a plain '60', I think that one
> is easy enough to understand from context. Naming the other constant
> is a good idea, I've now folded the change below into my patch.
>
> Thanks for the review!
>
> Arnd
>
> 8<-----
> diff --git a/fs/hfs/hfs_fs.h b/fs/hfs/hfs_fs.h
> index 26733051ee50..f71c384064c8 100644
> --- a/fs/hfs/hfs_fs.h
> +++ b/fs/hfs/hfs_fs.h
> @@ -247,22 +247,24 @@ extern void hfs_mark_mdb_dirty(struct super_block *sb);
> *
> * HFS implementations are highly inconsistent, this one matches the
> * traditional behavior of 64-bit Linux, giving the most useful
> * time range between 1970 and 2106, by treating any on-disk timestamp
> - * under 2082844800U (Jan 1 1970) as a time between 2040 and 2106.
> + * under HFS_UTC_OFFSET (Jan 1 1970) as a time between 2040 and 2106.
> */
> +#define HFS_UTC_OFFSET 2082844800U
> +
> static inline time64_t __hfs_m_to_utime(__be32 mt)
> {
> - time64_t ut = (u32)(be32_to_cpu(mt) - 2082844800U);
> + time64_t ut = (u32)(be32_to_cpu(mt) - HFS_UTC_OFFSET);
>
> return ut + sys_tz.tz_minuteswest * 60;
> }
>
> static inline __be32 __hfs_u_to_mtime(time64_t ut)
> {
> ut -= sys_tz.tz_minuteswest * 60;
>
> - return cpu_to_be32(lower_32_bits(ut) + 2082844800U);
> + return cpu_to_be32(lower_32_bits(ut) + HFS_UTC_OFFSET);
> }
> #define HFS_I(inode) (container_of(inode, struct hfs_inode_info, vfs_inode))
> #define HFS_SB(sb) ((struct hfs_sb_info *)(sb)->s_fs_info)
>
> diff --git a/fs/hfsplus/hfsplus_fs.h b/fs/hfsplus/hfsplus_fs.h
> index 22d0a22c41a3..3b03fff68543 100644
> --- a/fs/hfsplus/hfsplus_fs.h
> +++ b/fs/hfsplus/hfsplus_fs.h
> @@ -538,20 +538,22 @@ int hfsplus_read_wrapper(struct super_block *sb);
> *
> * HFS+ implementations are highly inconsistent, this one matches the
> * traditional behavior of 64-bit Linux, giving the most useful
> * time range between 1970 and 2106, by treating any on-disk timestamp
> - * under 2082844800U (Jan 1 1970) as a time between 2040 and 2106.
> + * under HFSPLUS_UTC_OFFSET (Jan 1 1970) as a time between 2040 and 2106.
> */
> +#define HFSPLUS_UTC_OFFSET 2082844800U
> +
> static inline time64_t __hfsp_mt2ut(__be32 mt)
> {
> - time64_t ut = (u32)(be32_to_cpu(mt) - 2082844800U);
> + time64_t ut = (u32)(be32_to_cpu(mt) - HFSPLUS_UTC_OFFSET);
>
> return ut;
> }
>
> static inline __be32 __hfsp_ut2mt(time64_t ut)
> {
> - return cpu_to_be32(lower_32_bits(ut) + 2082844800U);
> + return cpu_to_be32(lower_32_bits(ut) + HFSPLUS_UTC_OFFSET);
> }
>
> /* compatibility */
> #define hfsp_mt2ut(t) (struct timespec64){ .tv_sec = __hfsp_mt2ut(t) }

Looks good for me. I like the patch.

Reviewed-by: Vyacheslav Dubeyko <slava@dubeyko.com>

Thanks,
Vyacheslav Dubeyko.