linux-kernel - Re: [PATCH v5 1/2] sysctl: introduce new proc handler proc

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Date:   Wed, 4 Jan 2017 16:09:33 -0500
From:   "J. Bruce Fields" <bfields@...ldses.org>
To:     Jia He <hejianet@...il.com>
Cc:     linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Serge Hallyn <serge@...lyn.com>,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Kees Cook <keescook@...omium.org>,
        Hugh Dickins <hughd@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Daniel Cashman <dcashman@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Jeff Layton <jlayton@...chiereds.net>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        Anna Schumaker <anna.schumaker@...app.com>
Subject: Re: [PATCH v5 1/2] sysctl: introduce new proc handler proc_dobool

On Thu, Dec 15, 2016 at 03:24:20PM +0800, Jia He wrote:
> This is to let bool variable could be correctly displayed in
> big/little endian sysctl procfs. sizeof(bool) is arch dependent, 
> proc_dobool should work in all arches.

Did Alexey Debriyan agree that this dealt with his objections?

Also it'd be nice to have a sign-off from somebody that's actually
touched sysctl.c.  Then I could take it through the nfsd tree if that
doesn't cause anyone trouble.

--b.

> 
> Suggested-by: Pan Xinhui <xinhui@...ux.vnet.ibm.com>
> Signed-off-by: Jia He <hejianet@...il.com>
> ---
>  include/linux/sysctl.h |  2 ++
>  kernel/sysctl.c        | 41 +++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 43 insertions(+)
> 
> diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
> index adf4e51..255a9c7 100644
> --- a/include/linux/sysctl.h
> +++ b/include/linux/sysctl.h
> @@ -41,6 +41,8 @@ typedef int proc_handler (struct ctl_table *ctl, int write,
>  
>  extern int proc_dostring(struct ctl_table *, int,
>  			 void __user *, size_t *, loff_t *);
> +extern int proc_dobool(struct ctl_table *, int,
> +			void __user *, size_t *, loff_t *);
>  extern int proc_dointvec(struct ctl_table *, int,
>  			 void __user *, size_t *, loff_t *);
>  extern int proc_douintvec(struct ctl_table *, int,
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 706309f..c4bec65 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -2112,6 +2112,20 @@ static int proc_put_char(void __user **buf, size_t *size, char c)
>  	return 0;
>  }
>  
> +static int do_proc_dobool_conv(bool *negp, unsigned long *lvalp,
> +				int *valp,
> +				int write, void *data)
> +{
> +	if (write)
> +		*(bool *)valp = *lvalp;
> +	else {
> +		int val = *(bool *)valp;
> +
> +		*lvalp = (unsigned long)val;
> +	}
> +	return 0;
> +}
> +
>  static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp,
>  				 int *valp,
>  				 int write, void *data)
> @@ -2258,6 +2272,26 @@ static int do_proc_dointvec(struct ctl_table *table, int write,
>  }
>  
>  /**
> + * proc_dobool - read/write a bool
> + * @table: the sysctl table
> + * @write: %TRUE if this is a write to the sysctl file
> + * @buffer: the user buffer
> + * @lenp: the size of the user buffer
> + * @ppos: file position
> + *
> + * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
> + * values from/to the user buffer, treated as an ASCII string.
> + *
> + * Returns 0 on success.
> + */
> +int proc_dobool(struct ctl_table *table, int write,
> +		void __user *buffer, size_t *lenp, loff_t *ppos)
> +{
> +	return do_proc_dointvec(table, write, buffer, lenp, ppos,
> +				do_proc_dobool_conv, NULL);
> +}
> +
> +/**
>   * proc_dointvec - read a vector of integers
>   * @table: the sysctl table
>   * @write: %TRUE if this is a write to the sysctl file
> @@ -2885,6 +2919,12 @@ int proc_dostring(struct ctl_table *table, int write,
>  	return -ENOSYS;
>  }
>  
> +int proc_dobool(struct ctl_table *table, int write,
> +                  void __user *buffer, size_t *lenp, loff_t *ppos)
> +{
> +        return -ENOSYS;
> +}
> +
>  int proc_dointvec(struct ctl_table *table, int write,
>  		  void __user *buffer, size_t *lenp, loff_t *ppos)
>  {
> @@ -2941,6 +2981,7 @@ int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int write,
>   * No sense putting this after each symbol definition, twice,
>   * exception granted :-)
>   */
> +EXPORT_SYMBOL(proc_dobool);
>  EXPORT_SYMBOL(proc_dointvec);
>  EXPORT_SYMBOL(proc_douintvec);
>  EXPORT_SYMBOL(proc_dointvec_jiffies);
> -- 
> 2.5.5