netdev - Re: [PATCH -next 12/15] fs: dcache: move the sysctl into its own file

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Message-ID: <202408261253.D155EA0@keescook>
Date: Mon, 26 Aug 2024 12:56:00 -0700
From: Kees Cook <kees@...nel.org>
To: Kaixiong Yu <yukaixiong@...wei.com>
Cc: akpm@...ux-foundation.org, mcgrof@...nel.org,
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Subject: Re: [PATCH -next 12/15] fs: dcache: move the sysctl into its own file

On Mon, Aug 26, 2024 at 08:04:46PM +0800, Kaixiong Yu wrote:
> The sysctl_vfs_cache_pressure belongs to fs/dcache.c, move it to
> its own file from kernel/sysctl.c. As a part of fs/dcache.c cleaning,
> sysctl_vfs_cache_pressure is changed to a static variable, and export
> vfs_pressure_ratio with EXPORT_SYMBOL_GPL to be used by other files.
> And move the unneeded include(linux/dcache.h).
> 
> Signed-off-by: Kaixiong Yu <yukaixiong@...wei.com>
> ---
>  fs/dcache.c            | 21 +++++++++++++++++++--
>  include/linux/dcache.h |  7 +------
>  kernel/sysctl.c        |  9 ---------
>  3 files changed, 20 insertions(+), 17 deletions(-)
> 
> diff --git a/fs/dcache.c b/fs/dcache.c
> index 1af75fa68638..8717d5026cda 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -73,8 +73,13 @@
>   * If no ancestor relationship:
>   * arbitrary, since it's serialized on rename_lock
>   */
> -int sysctl_vfs_cache_pressure __read_mostly = 100;
> -EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
> +static int sysctl_vfs_cache_pressure __read_mostly = 100;
> +
> +unsigned long vfs_pressure_ratio(unsigned long val)
> +{
> +	return mult_frac(val, sysctl_vfs_cache_pressure, 100);
> +}
> +EXPORT_SYMBOL_GPL(vfs_pressure_ratio);

This was a static inline, but AFAICT it's only called through
alloc_super() which is hardly "fast path". If this series gets another
version it may be worth calling out this inline->out-of-line change in
the commit log.

I don't think it's a blocker, but I'm not a VFS maintainer. :)

-- 
Kees Cook