Re: [PATCH 3/4] dcache set size

[Dave Chinner <david@fromorbit.com>]

On Fri, Jul 29, 2011 at 05:44:18PM +0400, Glauber Costa wrote:
> Simple patch that provides a function allowing its caller to set
> the maximum number of dentries that can exist at the same time
> at a given super block. Will be used in a later patch.

Pretty simple - probably better to put it in the patch that uses it,
I think.

> Signed-off-by: Glauber Costa <glommer@parallels.com>
> CC: Dave Chinner <david@fromorbit.com>
> ---
>  fs/dcache.c            |   12 ++++++++++++
>  include/linux/dcache.h |    1 +
>  2 files changed, 13 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/dcache.c b/fs/dcache.c
> index 3bdb106..4369aa2 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -1202,6 +1202,18 @@ static int dcache_mem_check(struct super_block *sb)
>  	return -ENOMEM;
>  }
>  
> +int vfs_set_dcache_size(struct super_block *sb, int size)
> +{
> +	unsigned long dr = percpu_counter_sum_positive(&sb->s_nr_dentry); 
> +
> +	if (size != sb->s_nr_dentry_max)
> +		prune_dcache_sb(sb, dr - size);

And why shrink if the new size > the current sb->s_nr_dentry_max?

And what happens when size > dr?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com