linux-kernel - Re: [PATCH 1/3] hfs: stop using timespec based interfaces

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Date:   Tue, 31 Jul 2018 20:37:57 -0300
From:   Ernesto A. Fernández 
        <ernesto.mnd.fernandez@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        y2038@...ts.linaro.org, Jeff Layton <jlayton@...hat.com>,
        Jan Kara <jack@...e.cz>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] hfs: stop using timespec based interfaces

If you decide to go with this series after all:

On Tue, Jun 19, 2018 at 06:02:07PM +0200, Arnd Bergmann wrote:
> The native HFS timestamps overflow in year 2040, two years after the Unix
> y2038 overflow. However, the way that the conversion between on-disk
> timestamps and in-kernel timestamps was implemented, 64-bit machines
> actually ended up converting negative UTC timestamps (1902 through 1969)
> into times between 2038 and 2106.
> 
> Rather than making all machines faithfully represent timestamps in the
> ancient past but break after 2040, this changes the file system to
> always use the unsigned UTC interpretation, reading back times between
> 1970 and 2106.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  fs/hfs/hfs_fs.h | 6 ++++--
>  fs/hfs/inode.c  | 4 ++--
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/hfs/hfs_fs.h b/fs/hfs/hfs_fs.h
> index 6d0783e2e276..ff432931a5b1 100644
> --- a/fs/hfs/hfs_fs.h
> +++ b/fs/hfs/hfs_fs.h
> @@ -245,6 +245,8 @@ extern void hfs_mark_mdb_dirty(struct super_block *sb);
>   *	Unix:	unsigned lil-endian since 00:00 GMT, Jan. 1, 1970
>   *	mac:	unsigned big-endian since 00:00 GMT, Jan. 1, 1904
>   *
> + * We treat all timestamps before 1970 as times after 2038, so this
							 ^^^^
Same as the hfsplus patch, I find this confusing. I think it should say 2040.


Everything else looks good.

Reviewed-by: Ernesto A. Fernández <ernesto.mnd.fernandez@...il.com>

> + * actually works until year 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)
> @@ -252,9 +254,9 @@ extern void hfs_mark_mdb_dirty(struct super_block *sb);
>  #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)
>  
> -#define hfs_m_to_utime(time)	(struct timespec){ .tv_sec = __hfs_m_to_utime(time) }
> +#define hfs_m_to_utime(time)	(struct timespec64){ .tv_sec = __hfs_m_to_utime(time) }
>  #define hfs_u_to_mtime(time)	__hfs_u_to_mtime((time).tv_sec)
> -#define hfs_mtime()		__hfs_u_to_mtime(get_seconds())
> +#define hfs_mtime()		__hfs_u_to_mtime(ktime_get_real_seconds())
>  
>  static inline const char *hfs_mdb_name(struct super_block *sb)
>  {
> diff --git a/fs/hfs/inode.c b/fs/hfs/inode.c
> index 2a16111d312f..b3309b83371a 100644
> --- a/fs/hfs/inode.c
> +++ b/fs/hfs/inode.c
> @@ -351,7 +351,7 @@ static int hfs_read_inode(struct inode *inode, void *data)
>  		inode->i_mode &= ~hsb->s_file_umask;
>  		inode->i_mode |= S_IFREG;
>  		inode->i_ctime = inode->i_atime = inode->i_mtime =
> -				timespec_to_timespec64(hfs_m_to_utime(rec->file.MdDat));
> +				hfs_m_to_utime(rec->file.MdDat);
>  		inode->i_op = &hfs_file_inode_operations;
>  		inode->i_fop = &hfs_file_operations;
>  		inode->i_mapping->a_ops = &hfs_aops;
> @@ -362,7 +362,7 @@ static int hfs_read_inode(struct inode *inode, void *data)
>  		HFS_I(inode)->fs_blocks = 0;
>  		inode->i_mode = S_IFDIR | (S_IRWXUGO & ~hsb->s_dir_umask);
>  		inode->i_ctime = inode->i_atime = inode->i_mtime =
> -				timespec_to_timespec64(hfs_m_to_utime(rec->dir.MdDat));
> +				hfs_m_to_utime(rec->dir.MdDat);
>  		inode->i_op = &hfs_dir_inode_operations;
>  		inode->i_fop = &hfs_dir_operations;
>  		break;
> -- 
> 2.9.0
>