linux-kernel - Re: [PATCH] fs: add roundup_to_blocksize and bytes_to

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Date:	Wed, 22 Apr 2009 14:10:35 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Marcin Slusarz <marcin.slusarz@...il.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs: add roundup_to_blocksize and bytes_to_blocks helper
 functions

On Sun, 19 Apr 2009 20:42:15 +0200
Marcin Slusarz <marcin.slusarz@...il.com> wrote:

> bytes_to_blocks is open coded in more than 30 places
> roundup_to_blocksize is open coded in more than 15 places
> 

It would be nice to document these a bit.  Kernel-wide helpers..

> ---
>  include/linux/fs.h |   12 ++++++++++++
>  1 files changed, 12 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index e766be0..1b4e5b6 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2451,5 +2451,17 @@ int proc_nr_files(struct ctl_table *table, int write, struct file *filp,
>  
>  int get_filesystem_list(char * buf);
>  
> +static inline
> +unsigned long long roundup_to_blocksize(unsigned long long bytes, struct super_block *sb)
> +{
> +	return (bytes + sb->s_blocksize - 1) & ~(sb->s_blocksize - 1);

This is ALIGN(bytes, sb->s_blocksize).  Dunno if that's any clearer though.

> +}
> +
> +static inline
> +blkcnt_t bytes_to_blocks(unsigned long long bytes, struct super_block *sb)
> +{
> +	return (bytes + sb->s_blocksize - 1) >> sb->s_blocksize_bits;
> +}

I wonder whether `unsigned long long' was the best choice of type here.

Probably `bytes' should be loff_t.

roundup_to_blocksize() could/should return loff_t too, I think.

roundup_to_blocksize() isn't a terribly good name, IMO.  The name
conveys no sense of what the function returns.  It _sounds_ like it
returns a "block size".  But it doesn't - it returns a loff_t. 
round_up_file_offset_to_block_size() is a bit long though :(


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