From c7445339c13d98b83b5c739f056ff6e7a5af29bd Mon Sep 17 00:00:00 2001
From: Mohd Husaam Mehdi <husaam.mehdi@iopsys.eu>
Date: Fri, 5 Dec 2025 15:50:31 +0530
Subject: [PATCH] fluent-bit: avoid re-reading kmsg lines on every reload

---
 .../patches/0030-kmsg_avoid_reread.patch      | 103 ++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 fluent-bit/patches/0030-kmsg_avoid_reread.patch

diff --git a/fluent-bit/patches/0030-kmsg_avoid_reread.patch b/fluent-bit/patches/0030-kmsg_avoid_reread.patch
new file mode 100644
index 000000000..9b0147105
--- /dev/null
+++ b/fluent-bit/patches/0030-kmsg_avoid_reread.patch
@@ -0,0 +1,103 @@
+diff --git a/plugins/in_kmsg/in_kmsg.c b/plugins/in_kmsg/in_kmsg.c
+index 15f10545..481d162b 100644
+--- a/plugins/in_kmsg/in_kmsg.c
++++ b/plugins/in_kmsg/in_kmsg.c
+@@ -104,6 +104,32 @@ static int boot_time(struct timeval *boot_time)
+     return 0;
+ }
+ 
++static void load_last_sequence(struct flb_in_kmsg_config *ctx)
++{
++    FILE *f = fopen(FLB_KMSG_SEQ_MARKER, "r");
++    if (!f) {
++        ctx->last_sequence = 0;
++        return;
++    }
++
++    if (fscanf(f, "%llu", &ctx->last_sequence) != 1) {
++        ctx->last_sequence = 0;
++    }
++
++    fclose(f);
++}
++
++static void save_last_sequence(struct flb_in_kmsg_config *ctx)
++{
++    FILE *f = fopen(FLB_KMSG_SEQ_MARKER, "w");
++    if (!f) {
++        return;
++    }
++
++    fprintf(f, "%llu\n", (unsigned long long)ctx->last_sequence);
++    fclose(f);
++}
++
+ static inline int process_line(const char *line,
+                                struct flb_input_instance *i_ins,
+                                struct flb_in_kmsg_config *ctx)
+@@ -161,6 +187,11 @@ static inline int process_line(const char *line,
+     }
+ 
+     sequence = val;
++    /* skip lines we have already seen */
++    if (sequence <= ctx->last_sequence) {
++        return 0;   /* skip old message */
++    }
++
+     p = ++end;
+ 
+     /* Timestamp */
+@@ -225,6 +256,7 @@ static inline int process_line(const char *line,
+                              ctx->log_encoder.output_buffer,
+                              ctx->log_encoder.output_length);
+ 
++        ctx->last_sequence = sequence;
+         ret = 0;
+     }
+     else {
+@@ -363,6 +395,10 @@ static int in_kmsg_init(struct flb_input_instance *ins,
+         return -1;
+     }
+ 
++    load_last_sequence(ctx);
++    flb_plg_debug(ctx->ins, "restored last_sequence=%llu",
++                  (unsigned long long)ctx->last_sequence);
++
+     return 0;
+ }
+ 
+@@ -373,6 +409,12 @@ static int in_kmsg_exit(void *data, struct flb_config *config)
+ 
+     flb_log_event_encoder_destroy(&ctx->log_encoder);
+ 
++    /*
++     * save the last read sequence number in a file,
++     * so that we know where to start next time
++     */
++    save_last_sequence(ctx);
++
+     if (ctx->fd >= 0) {
+         close(ctx->fd);
+     }
+diff --git a/plugins/in_kmsg/in_kmsg.h b/plugins/in_kmsg/in_kmsg.h
+index 0ea2e97a..4b9d98fd 100644
+--- a/plugins/in_kmsg/in_kmsg.h
++++ b/plugins/in_kmsg/in_kmsg.h
+@@ -27,6 +27,7 @@
+ #include <stdint.h>
+ 
+ #define FLB_KMSG_DEV        "/dev/kmsg"
++#define FLB_KMSG_SEQ_MARKER "/tmp/fluent_bit_kmsg_last_seq"
+ #define FLB_KMSG_BUF_SIZE   4096
+ 
+ /* Alert levels, taken from util-linux sources */
+@@ -60,6 +61,9 @@ struct flb_in_kmsg_config {
+     size_t buf_size;
+     struct flb_log_event_encoder log_encoder;
+     struct flb_input_instance *ins;
++
++    uint64_t last_sequence;           /* last saved sequence */
++    const char *seq_file;             /* path to seq file */
+ };
+ 
+