linux-kernel - Re: [PATCH 1/9] syslog_ns: add syslog_namespace and put/get_syslog

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Message-ID: <51F6388B.8000308@cn.fujitsu.com>
Date:	Mon, 29 Jul 2013 17:40:27 +0800
From:	Gu Zheng <guz.fnst@...fujitsu.com>
To:	Rui Xiang <rui.xiang@...wei.com>
CC:	containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, serge.hallyn@...ntu.com,
	ebiederm@...ssion.com, akpm@...ux-foundation.org,
	gaofeng@...fujitsu.com, libo.chen@...wei.com
Subject: Re: [PATCH 1/9] syslog_ns: add syslog_namespace and put/get_syslog_ns

Hi Rui,
	Refer to inline:).

On 07/29/2013 10:31 AM, Rui Xiang wrote:

> Add a struct syslog_namespace which contains the necessary
> members for hanlding syslog and realize get_syslog_ns and
> put_syslog_ns API.
> 
> Signed-off-by: Rui Xiang <rui.xiang@...wei.com>
> ---
>  include/linux/syslog.h | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  kernel/printk.c        |  7 ------
>  2 files changed, 68 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/syslog.h b/include/linux/syslog.h
> index 98a3153..425fafe 100644
> --- a/include/linux/syslog.h
> +++ b/include/linux/syslog.h
> @@ -21,6 +21,9 @@
>  #ifndef _LINUX_SYSLOG_H
>  #define _LINUX_SYSLOG_H
>  
> +#include <linux/slab.h>
> +#include <linux/kref.h>
> +
>  /* Close the log.  Currently a NOP. */
>  #define SYSLOG_ACTION_CLOSE          0
>  /* Open the log. Currently a NOP. */
> @@ -47,6 +50,71 @@
>  #define SYSLOG_FROM_READER           0
>  #define SYSLOG_FROM_PROC             1
>  
> +enum log_flags {
> +	LOG_NOCONS      = 1,    /* already flushed, do not print to console */
> +	LOG_NEWLINE     = 2,    /* text ended with a newline */
> +	LOG_PREFIX      = 4,    /* text started with a prefix */
> +	LOG_CONT        = 8,    /* text is a fragment of a continuation line */
> +};
> +
> +struct syslog_namespace {
> +	struct kref kref;	/* syslog_ns reference count & control */
> +
> +	raw_spinlock_t logbuf_lock; /* access conflict locker */
> +	/* cpu currently holding logbuf_lock of ns */
> +	unsigned int logbuf_cpu;
> +
> +	/* index and sequence number of the first record stored in the buffer */
> +	u64 log_first_seq;
> +	u32 log_first_idx;
> +
> +	/* index and sequence number of the next record stored in the buffer */
> +	u64 log_next_seq;
> +	u32 log_next_idx;
> +
> +	/* the next printk record to read after the last 'clear' command */
> +	u64 clear_seq;
> +	u32 clear_idx;
> +
> +	char *log_buf;
> +	u32 log_buf_len;
> +
> +	/* the next printk record to write to the console */
> +	u64 console_seq;
> +	u32 console_idx;
> +
> +	/* the next printk record to read by syslog(READ) or /proc/kmsg */
> +	u64 syslog_seq;
> +	u32 syslog_idx;
> +	enum log_flags syslog_prev;
> +	size_t syslog_partial;
> +
> +	int dmesg_restrict;
> +};
> +
> +static inline struct syslog_namespace *get_syslog_ns(
> +				struct syslog_namespace *ns)
> +{
> +	if (ns)
> +		kref_get(&ns->kref);
> +	return ns;
> +}
> +
> +static inline void free_syslog_ns(struct kref *kref)
> +{
> +	struct syslog_namespace *ns;
> +	ns = container_of(kref, struct syslog_namespace, kref);
> +
> +	kfree(ns->log_buf);
> +	kfree(ns);
> +}

This interface seems a bit ugly, why not use the format like put_syslog_ns()?

static inline void free_syslog_ns(struct syslog_namespace *ns)

> +
> +static inline void put_syslog_ns(struct syslog_namespace *ns)
> +{
> +	if (ns)
> +		kref_put(&ns->kref, free_syslog_ns);
> +}
> +
>  int do_syslog(int type, char __user *buf, int count, bool from_file);
>  
>  #endif /* _LINUX_SYSLOG_H */
> diff --git a/kernel/printk.c b/kernel/printk.c
> index d37d45c..7e544bf 100644
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
> @@ -193,13 +193,6 @@ static int console_may_schedule;
>   * separated by ',', and find the message after the ';' character.
>   */
>  
> -enum log_flags {
> -	LOG_NOCONS	= 1,	/* already flushed, do not print to console */
> -	LOG_NEWLINE	= 2,	/* text ended with a newline */
> -	LOG_PREFIX	= 4,	/* text started with a prefix */
> -	LOG_CONT	= 8,	/* text is a fragment of a continuation line */
> -};
> -
>  struct log {
>  	u64 ts_nsec;		/* timestamp in nanoseconds */
>  	u16 len;		/* length of entire record */


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