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SubjectRe: [PATCH 8/9] syslog_ns: implement ns_printk for specific syslog_ns
Hi Rui,

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

> Add a new interface named ns_printk, and assign an
> patamater ns. Log which belong to a container can
> be printed by ns_printk.

One question, with the syslog_ns used, do the log we print by *printk* in the
host contains the log in each syslog_ns(print out with ns_printk) or not?

Thanks,
Gu

>
> Signed-off-by: Rui Xiang <rui.xiang@huawei.com>
> ---
> include/linux/printk.h | 4 ++++
> kernel/printk.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++----
> 2 files changed, 53 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/printk.h b/include/linux/printk.h
> index 29e3f85..bf83ad9 100644
> --- a/include/linux/printk.h
> +++ b/include/linux/printk.h
> @@ -6,6 +6,7 @@
> #include <linux/kern_levels.h>
> #include <linux/linkage.h>
>
> +struct syslog_namespace;
> extern const char linux_banner[];
> extern const char linux_proc_banner[];
>
> @@ -123,6 +124,9 @@ asmlinkage int printk_emit(int facility, int level,
> asmlinkage __printf(1, 2) __cold
> int printk(const char *fmt, ...);
>
> +asmlinkage __printf(2, 3) __cold
> +int ns_printk(struct syslog_namespace *ns, const char *fmt, ...);
> +
> /*
> * Special printk facility for scheduler use only, _DO_NOT_USE_ !
> */
> diff --git a/kernel/printk.c b/kernel/printk.c
> index 6b561db..56a8b27 100644
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
> @@ -1554,9 +1554,10 @@ static size_t cont_print_text(char *text, size_t size)
> return textlen;
> }
>
> -asmlinkage int vprintk_emit(int facility, int level,
> - const char *dict, size_t dictlen,
> - const char *fmt, va_list args)
> +static int ns_vprintk_emit(int facility, int level,
> + const char *dict, size_t dictlen,
> + const char *fmt, va_list args,
> + struct syslog_namespace *ns)
> {
> static int recursion_bug;
> static char textbuf[LOG_LINE_MAX];
> @@ -1566,7 +1567,6 @@ asmlinkage int vprintk_emit(int facility, int level,
> unsigned long flags;
> int this_cpu;
> int printed_len = 0;
> - struct syslog_namespace *ns = &init_syslog_ns;
>
> boot_delay_msec(level);
> printk_delay();
> @@ -1697,6 +1697,14 @@ out_restore_irqs:
>
> return printed_len;
> }
> +
> +asmlinkage int vprintk_emit(int facility, int level,
> + const char *dict, size_t dictlen,
> + const char *fmt, va_list args)
> +{
> + return ns_vprintk_emit(facility, level, dict, dictlen, fmt, args,
> + &init_syslog_ns);
> +}
> EXPORT_SYMBOL(vprintk_emit);
>
> asmlinkage int vprintk(const char *fmt, va_list args)
> @@ -1762,6 +1770,43 @@ asmlinkage int printk(const char *fmt, ...)
> }
> EXPORT_SYMBOL(printk);
>
> +/**
> + * ns_printk - print a kernel message in syslog_ns
> + * @ns: syslog namespace
> + * @fmt: format string
> + *
> + * This is ns_printk().
> + * It can be called from container context. We add a param
> + * ns to record current syslog namespace, because we need to
> + * print some log which are not generated by host, but contaner.
> + *
> + * See the vsnprintf() documentation for format string extensions over C99.
> + **/
> +asmlinkage int ns_printk(struct syslog_namespace *ns,
> + const char *fmt, ...)
> +{
> + va_list args;
> + int r;
> +
> + if (!ns)
> + ns = current_user_ns()->syslog_ns;
> +
> +#ifdef CONFIG_KGDB_KDB
> + if (unlikely(kdb_trap_printk)) {
> + va_start(args, fmt);
> + r = vkdb_printf(fmt, args);
> + va_end(args);
> + return r;
> + }
> +#endif
> + va_start(args, fmt);
> + r = ns_vprintk_emit(0, -1, NULL, 0, fmt, args, ns);
> + va_end(args);
> +
> + return r;
> +}
> +EXPORT_SYMBOL(ns_printk);
> +

Here can we do some clean up to printk using ns_printk?

> #else /* CONFIG_PRINTK */
>
> #define LOG_LINE_MAX 0




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