[Devel] [PATCH RHEL7 COMMIT] ve/printk: add ve_log_printk() for log in !current->task_ve

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-514.6.1.vz7.28.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-514.6.1.vz7.28.2
------>
commit 48477a16267e71d9794497feb58e8170a3c7c9fe
Author: Dmitry Safonov <dsafonov at virtuozzo.com>
Date:   Fri Jan 20 19:49:45 2017 +0400

    ve/printk: add ve_log_printk() for log in !current->task_ve
    
    Patchset description:
    iptables LOG in CT
    
    With these patches, iptables LOG is printed into CT's dmesg buffer.
    Yet it doesn't show in /var/log/messages and I believe the reason
    is the absence of /dev/kmsg in CT (and rsyslog doesn't do redirection
    for log entries thou). Dev kmsg is virtualized, so looks like nothing
    prevents adding it to libvzctl list of devtmpfs devices:
    https://github.com/OpenVZ/libvzctl/blob/55ebf21b03d408f0faaaecaab08b74eb2dce0e70/lib/env.c#L614
    Also it should fix follow-log for `dmesg -w`.
    
    These patches make iptables LOG visible in CT's `dmesg`.
    
    Dmitry Safonov (3):
      ve/printk: add ve_log_printk() for log in !current->task_ve
      netfilter: rectify nflog inside CT
      netfilter: rectify ebtlog inside CT
    
    ==========================
    This patch description:
    
    In some places we want to log into non-current VE.
    So here is ve_log_printk(), which prints message from any printk-valid
    context to other VE's buffer.
    This changes current behavior a little as erstwhile we've logged only
    into current VE's buffer, but looking at __vprintk_emit()'s locks it
    should be safe (but still little dangerous as it introduces new, untested
    previously call-path).
    
    https://jira.sw.ru/browse/PSBM-54183
    
    Signed-off-by: Dmitry Safonov <dsafonov at virtuozzo.com>
    Reviewed-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 include/linux/printk.h |  7 +++++++
 kernel/printk.c        | 16 ++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index d93fbfe..fc35b47 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -135,6 +135,8 @@ int ve_printk(int dst, const char *fmt, ...);
 
 int ve_log_init(struct ve_struct *ve);
 void ve_log_destroy(struct ve_struct *ve);
+asmlinkage __printf(2, 3) __cold
+int ve_log_printk(struct ve_struct *ve, const char *s, ...);
 
 /*
  * Special printk facility for scheduler/timekeeping use only, _DO_NOT_USE_ !
@@ -194,6 +196,11 @@ static inline
 void ve_log_destroy(struct ve_struct *ve)
 {
 }
+static inline __printf(2, 3) __cold
+int ve_log_printk(struct ve_struct *ve, const char *s, ...)
+{
+	return 0;
+}
 static inline __printf(1, 2) __cold
 int printk_deferred(const char *s, ...)
 {
diff --git a/kernel/printk.c b/kernel/printk.c
index a332be1..47cddb3 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1900,6 +1900,22 @@ asmlinkage int ve_printk(int dst, const char *fmt, ...)
 }
 EXPORT_SYMBOL(ve_printk);
 
+asmlinkage int ve_log_printk(struct ve_struct *ve, const char *fmt, ...)
+{
+	struct log_state *log = &init_log_state;
+	va_list args;
+	int r;
+
+	if (likely(ve && ve->log_state))
+		log = ve->log_state;
+
+	va_start(args, fmt);
+	r = __vprintk_emit(log, 0, -1, NULL, 0, fmt, args);
+	va_end(args);
+
+	return r;
+}
+EXPORT_SYMBOL(ve_log_printk);
 /**
  * printk - print a kernel message
  * @fmt: format string