linux-kernel - Re: [PATCH 2/3] hfsplus: stop using timespec based interfaces

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Date:   Sun, 24 Jun 2018 00:11:41 -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, Vyacheslav Dubeyko <slava@...eyko.com>,
        Jan Kara <jack@...e.cz>,
        Dave Kleikamp <dave.kleikamp@...cle.com>,
        Jeff Layton <jlayton@...hat.com>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] hfsplus: stop using timespec based interfaces

On Tue, Jun 19, 2018 at 06:02:08PM +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/hfsplus/hfsplus_fs.h |  7 ++++---
>  fs/hfsplus/inode.c      | 12 ++++++------
>  2 files changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/hfsplus/hfsplus_fs.h b/fs/hfsplus/hfsplus_fs.h
> index d9255abafb81..646c207be38d 100644
> --- a/fs/hfsplus/hfsplus_fs.h
> +++ b/fs/hfsplus/hfsplus_fs.h
> @@ -530,13 +530,14 @@ int hfsplus_submit_bio(struct super_block *sb, sector_t sector, void *buf,
>  		       void **data, int op, int op_flags);
>  int hfsplus_read_wrapper(struct super_block *sb);
>  
> -/* time macros */
> +/* time macros: convert between 1904-2040 and 1970-2106 range,
> + * pre-1970 timestamps are interpreted as post-2038 times after wrap-around
						  ^^^^
If we are talking about on-disk timestamps, this should be 2040.


Everything else looks fine, if it helps you can use:

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

> */
>  #define __hfsp_mt2ut(t)		(be32_to_cpu(t) - 2082844800U)
>  #define __hfsp_ut2mt(t)		(cpu_to_be32(t + 2082844800U))
>  
>  /* compatibility */
> -#define hfsp_mt2ut(t)		(struct timespec){ .tv_sec = __hfsp_mt2ut(t) }
> +#define hfsp_mt2ut(t)		(struct timespec64){ .tv_sec = __hfsp_mt2ut(t) }
>  #define hfsp_ut2mt(t)		__hfsp_ut2mt((t).tv_sec)
> -#define hfsp_now2mt()		__hfsp_ut2mt(get_seconds())
> +#define hfsp_now2mt()		__hfsp_ut2mt(ktime_get_real_seconds())
>  
>  #endif
> diff --git a/fs/hfsplus/inode.c b/fs/hfsplus/inode.c
> index c824f702feec..c0c8d433864f 100644
> --- a/fs/hfsplus/inode.c
> +++ b/fs/hfsplus/inode.c
> @@ -493,9 +493,9 @@ int hfsplus_cat_read_inode(struct inode *inode, struct hfs_find_data *fd)
>  		hfsplus_get_perms(inode, &folder->permissions, 1);
>  		set_nlink(inode, 1);
>  		inode->i_size = 2 + be32_to_cpu(folder->valence);
> -		inode->i_atime = timespec_to_timespec64(hfsp_mt2ut(folder->access_date));
> -		inode->i_mtime = timespec_to_timespec64(hfsp_mt2ut(folder->content_mod_date));
> -		inode->i_ctime = timespec_to_timespec64(hfsp_mt2ut(folder->attribute_mod_date));
> +		inode->i_atime = hfsp_mt2ut(folder->access_date);
> +		inode->i_mtime = hfsp_mt2ut(folder->content_mod_date);
> +		inode->i_ctime = hfsp_mt2ut(folder->attribute_mod_date);
>  		HFSPLUS_I(inode)->create_date = folder->create_date;
>  		HFSPLUS_I(inode)->fs_blocks = 0;
>  		if (folder->flags & cpu_to_be16(HFSPLUS_HAS_FOLDER_COUNT)) {
> @@ -531,9 +531,9 @@ int hfsplus_cat_read_inode(struct inode *inode, struct hfs_find_data *fd)
>  			init_special_inode(inode, inode->i_mode,
>  					   be32_to_cpu(file->permissions.dev));
>  		}
> -		inode->i_atime = timespec_to_timespec64(hfsp_mt2ut(file->access_date));
> -		inode->i_mtime = timespec_to_timespec64(hfsp_mt2ut(file->content_mod_date));
> -		inode->i_ctime = timespec_to_timespec64(hfsp_mt2ut(file->attribute_mod_date));
> +		inode->i_atime = hfsp_mt2ut(file->access_date);
> +		inode->i_mtime = hfsp_mt2ut(file->content_mod_date);
> +		inode->i_ctime = hfsp_mt2ut(file->attribute_mod_date);
>  		HFSPLUS_I(inode)->create_date = file->create_date;
>  	} else {
>  		pr_err("bad catalog entry used to create inode\n");
> -- 
> 2.9.0
>