The commit is pushed to "branch-rh9-5.14.vz9.1.x-ovz" and will appear at 
https://src.openvz.org/scm/ovz/vzkernel.git
after ark-5.14
------>
commit 27c8a8c7a2bdfabee45bd6cf778a9f555ebf4f6f
Author: Vladimir Davydov <vdavydov....@gmail.com>
Date:   Wed Sep 29 21:26:05 2021 +0300

    ve/printk: Virtualize syslog_*
    
    https://jira.sw.ru/browse/PSBM-17899
    
    Signed-off-by: Vladimir Davydov <vdavy...@parallels.com>
    Signed-off-by: Stanislav Kinsburskiy <skinsbur...@virtuozzo.com>
    
    +++
    ve/printk: Fix printk virtualization
    
    ve_printk() corrupts host's dmesg:
            # dmesg|wc -l
            599
            # vzctl create 101
            # vzctl set 101 --netif_add eth0 --save
            # vzctl start 101
            # vzctl exec 101 'tcpdump -w tcpdump.out -U -n -i eth0 esp'
            # dmesg|wc -l
            2
    
    Add missing parts of prinkt virtualization to fix this.
    
    https://jira.sw.ru/browse/PSBM-17899
    https://jira.sw.ru/browse/PSBM-105442
    
    Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
    
    Rebasing to vz9: part of vz8 commit:
     d63aeb311a64 ("ve/printk: printk virtualization")
    
    https://jira.sw.ru/browse/PSBM-133985
    
    Signed-off-by: Konstantin Khorenko <khore...@virtuozzo.com>
---
 kernel/printk/printk.c | 59 +++++++++++++++++++++++++-------------------------
 1 file changed, 30 insertions(+), 29 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index a1dedbc88426..a994c2fe19c7 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -361,12 +361,6 @@ static DEFINE_RAW_SPINLOCK(syslog_lock);
 
 #ifdef CONFIG_PRINTK
 DECLARE_WAIT_QUEUE_HEAD(log_wait);
-/* All 3 protected by @syslog_lock. */
-/* the next printk record to read by syslog(READ) or /proc/kmsg */
-static u64 syslog_seq;
-static size_t syslog_partial;
-static bool syslog_time;
-
 /* All 3 protected by @console_sem. */
 /* the next printk record to write to the console */
 static u64 console_seq;
@@ -418,6 +412,12 @@ static struct log_state {
        char *buf;
        u32 buf_len;
 
+       /* All 3 protected by @syslog_lock. */
+       /* the next printk record to read by syslog(READ) or /proc/kmsg */
+       u64 syslog_seq;
+       size_t syslog_partial;
+       bool syslog_time;
+
        /*
         * The next printk record to read after the last 'clear' command. There 
are
         * two copies (updated with seqcount_latch) so that reads can locklessly
@@ -1546,35 +1546,35 @@ static int syslog_print(struct log_state *log,
 
                printk_safe_enter_irq();
                raw_spin_lock(&syslog_lock);
-               if (!prb_read_valid(log->prb, syslog_seq, &r)) {
+               if (!prb_read_valid(log->prb, log->syslog_seq, &r)) {
                        raw_spin_unlock(&syslog_lock);
                        printk_safe_exit_irq();
                        break;
                }
-               if (r.info->seq != syslog_seq) {
+               if (r.info->seq != log->syslog_seq) {
                        /* message is gone, move to next valid one */
-                       syslog_seq = r.info->seq;
-                       syslog_partial = 0;
+                       log->syslog_seq = r.info->seq;
+                       log->syslog_partial = 0;
                }
 
                /*
                 * To keep reading/counting partial line consistent,
                 * use printk_time value as of the beginning of a line.
                 */
-               if (!syslog_partial)
-                       syslog_time = printk_time;
+               if (!log->syslog_partial)
+                       log->syslog_time = printk_time;
 
-               skip = syslog_partial;
-               n = record_print_text(&r, true, syslog_time);
-               if (n - syslog_partial <= size) {
+               skip = log->syslog_partial;
+               n = record_print_text(&r, true, log->syslog_time);
+               if (n - log->syslog_partial <= size) {
                        /* message fits into buffer, move forward */
-                       syslog_seq = r.info->seq + 1;
-                       n -= syslog_partial;
-                       syslog_partial = 0;
+                       log->syslog_seq = r.info->seq + 1;
+                       n -= log->syslog_partial;
+                       log->syslog_partial = 0;
                } else if (!len){
                        /* partial read(), remember position */
                        n = size;
-                       syslog_partial += n;
+                       log->syslog_partial += n;
                } else
                        n = 0;
                raw_spin_unlock(&syslog_lock);
@@ -1669,10 +1669,11 @@ static void syslog_clear(struct log_state *log)
 /* Return a consistent copy of @syslog_seq. */
 static u64 read_syslog_seq_irq(void)
 {
+       struct log_state *log = ve_log_state();
        u64 seq;
 
        raw_spin_lock_irq(&syslog_lock);
-       seq = syslog_seq;
+       seq = log->syslog_seq;
        raw_spin_unlock_irq(&syslog_lock);
 
        return seq;
@@ -1707,7 +1708,7 @@ int do_syslog(int type, char __user *buf, int len, int 
source)
                                prb_read_valid(log->prb, read_syslog_seq_irq(), 
NULL));
                if (error)
                        return error;
-               error = syslog_print(buf, len);
+               error = syslog_print(log, buf, len);
                break;
        /* Read/clear last kernel messages */
        case SYSLOG_ACTION_READ_CLEAR:
@@ -1760,10 +1761,10 @@ int do_syslog(int type, char __user *buf, int len, int 
source)
                        printk_safe_exit_irq();
                        return 0;
                }
-               if (info.seq != syslog_seq) {
+               if (info.seq != log->syslog_seq) {
                        /* messages are gone, move to first one */
-                       syslog_seq = info.seq;
-                       syslog_partial = 0;
+                       log->syslog_seq = info.seq;
+                       log->syslog_partial = 0;
                }
                if (source == SYSLOG_FROM_PROC) {
                        /*
@@ -1771,9 +1772,9 @@ int do_syslog(int type, char __user *buf, int len, int 
source)
                         * for pending data, not the size; return the count of
                         * records, not the length.
                         */
-                       error = prb_next_seq(log->prb) - syslog_seq;
+                       error = prb_next_seq(log->prb) - log->syslog_seq;
                } else {
-                       bool time = syslog_partial ? syslog_time : printk_time;
+                       bool time = log->syslog_partial ? log->syslog_time : 
printk_time;
                        unsigned int line_count;
                        u64 seq;
 
@@ -1783,7 +1784,7 @@ int do_syslog(int type, char __user *buf, int len, int 
source)
                                                                    true, time);
                                time = printk_time;
                        }
-                       error -= syslog_partial;
+                       error -= log->syslog_partial;
                }
                raw_spin_unlock(&syslog_lock);
                printk_safe_exit_irq();
@@ -2301,7 +2302,6 @@ EXPORT_SYMBOL(printk);
 #define prb_read_valid(rb, seq, r)     false
 #define prb_first_valid_seq(rb)                0
 
-static u64 syslog_seq;
 static u64 console_seq;
 static u64 exclusive_console_stop_seq;
 static unsigned long console_dropped;
@@ -2945,6 +2945,7 @@ static int try_enable_new_console(struct console *newcon, 
bool user_specified)
  */
 void register_console(struct console *newcon)
 {
+       struct log_state *log = &init_log_state;
        unsigned long flags;
        struct console *bcon = NULL;
        int err;
@@ -3051,7 +3052,7 @@ void register_console(struct console *newcon)
 
                /* Get a consistent copy of @syslog_seq. */
                raw_spin_lock_irqsave(&syslog_lock, flags);
-               console_seq = syslog_seq;
+               console_seq = log->syslog_seq;
                raw_spin_unlock_irqrestore(&syslog_lock, flags);
        }
        console_unlock();
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