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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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