Re: [PATCH 15/29] ext4: Deprecate max_writeback_mb_bump sysfs attribute

[Zheng Liu <gnehzuil.liu@gmail.com>]

On Mon, Apr 08, 2013 at 11:32:20PM +0200, Jan Kara wrote:
> This attribute is now unused so deprecate it. We still show the old
> default value to keep some compatibility but we don't allow writing to
> that attribute anymore.

I think we can remove it completely.  IMHO, if an application tries to
set this value, it will get an error because now it can't set it.

Regards,
                                                - Zheng

> 
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  fs/ext4/ext4.h  |    1 -
>  fs/ext4/super.c |   30 ++++++++++++++++++++++++------
>  2 files changed, 24 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index edf9b9e..3575fdb 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1234,7 +1234,6 @@ struct ext4_sb_info {
>  	unsigned int s_mb_stats;
>  	unsigned int s_mb_order2_reqs;
>  	unsigned int s_mb_group_prealloc;
> -	unsigned int s_max_writeback_mb_bump;
>  	unsigned int s_max_dir_size_kb;
>  	/* where last allocation was done - for stream allocation */
>  	unsigned long s_mb_last_group;
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 34e8552..09ff724 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -2374,7 +2374,10 @@ struct ext4_attr {
>  	ssize_t (*show)(struct ext4_attr *, struct ext4_sb_info *, char *);
>  	ssize_t (*store)(struct ext4_attr *, struct ext4_sb_info *,
>  			 const char *, size_t);
> -	int offset;
> +	union {
> +		int offset;
> +		int deprecated_val;
> +	} u;
>  };
>  
>  static int parse_strtoul(const char *buf,
> @@ -2443,7 +2446,7 @@ static ssize_t inode_readahead_blks_store(struct ext4_attr *a,
>  static ssize_t sbi_ui_show(struct ext4_attr *a,
>  			   struct ext4_sb_info *sbi, char *buf)
>  {
> -	unsigned int *ui = (unsigned int *) (((char *) sbi) + a->offset);
> +	unsigned int *ui = (unsigned int *) (((char *) sbi) + a->u.offset);
>  
>  	return snprintf(buf, PAGE_SIZE, "%u\n", *ui);
>  }
> @@ -2452,7 +2455,7 @@ static ssize_t sbi_ui_store(struct ext4_attr *a,
>  			    struct ext4_sb_info *sbi,
>  			    const char *buf, size_t count)
>  {
> -	unsigned int *ui = (unsigned int *) (((char *) sbi) + a->offset);
> +	unsigned int *ui = (unsigned int *) (((char *) sbi) + a->u.offset);
>  	unsigned long t;
>  
>  	if (parse_strtoul(buf, 0xffffffff, &t))
> @@ -2478,12 +2481,20 @@ static ssize_t trigger_test_error(struct ext4_attr *a,
>  	return count;
>  }
>  
> +static ssize_t sbi_deprecated_show(struct ext4_attr *a,
> +				   struct ext4_sb_info *sbi, char *buf)
> +{
> +	return snprintf(buf, PAGE_SIZE, "%d\n", a->u.deprecated_val);
> +}
> +
>  #define EXT4_ATTR_OFFSET(_name,_mode,_show,_store,_elname) \
>  static struct ext4_attr ext4_attr_##_name = {			\
>  	.attr = {.name = __stringify(_name), .mode = _mode },	\
>  	.show	= _show,					\
>  	.store	= _store,					\
> -	.offset = offsetof(struct ext4_sb_info, _elname),	\
> +	.u = {							\
> +		.offset = offsetof(struct ext4_sb_info, _elname),\
> +	},							\
>  }
>  #define EXT4_ATTR(name, mode, show, store) \
>  static struct ext4_attr ext4_attr_##name = __ATTR(name, mode, show, store)
> @@ -2494,6 +2505,14 @@ static struct ext4_attr ext4_attr_##name = __ATTR(name, mode, show, store)
>  #define EXT4_RW_ATTR_SBI_UI(name, elname)	\
>  	EXT4_ATTR_OFFSET(name, 0644, sbi_ui_show, sbi_ui_store, elname)
>  #define ATTR_LIST(name) &ext4_attr_##name.attr
> +#define EXT4_DEPRECATED_ATTR(_name, _val)	\
> +static struct ext4_attr ext4_attr_##_name = {			\
> +	.attr = {.name = __stringify(_name), .mode = 0444 },	\
> +	.show	= sbi_deprecated_show,				\
> +	.u = {							\
> +		.deprecated_val = _val,				\
> +	},							\
> +}
>  
>  EXT4_RO_ATTR(delayed_allocation_blocks);
>  EXT4_RO_ATTR(session_write_kbytes);
> @@ -2507,7 +2526,7 @@ EXT4_RW_ATTR_SBI_UI(mb_min_to_scan, s_mb_min_to_scan);
>  EXT4_RW_ATTR_SBI_UI(mb_order2_req, s_mb_order2_reqs);
>  EXT4_RW_ATTR_SBI_UI(mb_stream_req, s_mb_stream_request);
>  EXT4_RW_ATTR_SBI_UI(mb_group_prealloc, s_mb_group_prealloc);
> -EXT4_RW_ATTR_SBI_UI(max_writeback_mb_bump, s_max_writeback_mb_bump);
> +EXT4_DEPRECATED_ATTR(max_writeback_mb_bump, 128);
>  EXT4_RW_ATTR_SBI_UI(extent_max_zeroout_kb, s_extent_max_zeroout_kb);
>  EXT4_ATTR(trigger_fs_error, 0200, NULL, trigger_test_error);
>  
> @@ -3718,7 +3737,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  	}
>  
>  	sbi->s_stripe = ext4_get_stripe_size(sbi);
> -	sbi->s_max_writeback_mb_bump = 128;
>  	sbi->s_extent_max_zeroout_kb = 32;
>  
>  	/* Register extent status tree shrinker */
> -- 
> 1.7.1
> 
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