linux-kernel - [PATCH v2 4/5] pstore/ram: allow to dump kmesg during regular reboot

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Date:   Tue,  5 May 2020 11:45:09 -0400
From:   Pavel Tatashin <pasha.tatashin@...een.com>
To:     pasha.tatashin@...een.com, jmorris@...ei.org, sashal@...nel.org,
        linux-kernel@...r.kernel.org, pmladek@...e.com,
        sergey.senozhatsky@...il.com, rostedt@...dmis.org,
        keescook@...omium.org, anton@...msg.org, ccross@...roid.com,
        tony.luck@...el.com, robh+dt@...nel.org, devicetree@...r.kernel.org
Subject: [PATCH v2 4/5] pstore/ram: allow to dump kmesg during regular reboot

Currently, ramoops is capable to collect dmesg buffer only during
panic and oops events. However, it is desirable to optionally allow
collecting dmesg buffers during other events as well: reboot, kexec,
emergency reboot etc.

While, a similar functionality is provided by pstore console it is not the
same. Often, console message level is reduced in production due to baud
rate limitation of serial consoles.  Having a noisy console reduces the
boot performance.

Thus, if the shutdown dmesg buffer is needed to study the shutdown
performance, it is currently not possible to do so with console as by
increasing the console output the shutdown time substantially increases
as well.

Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
---
 fs/pstore/ram.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 223581aeea96..568d9911beae 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -60,7 +60,12 @@ MODULE_PARM_DESC(mem_type,
 static int dump_oops = 1;
 module_param(dump_oops, int, 0600);
 MODULE_PARM_DESC(dump_oops,
-		"set to 1 to dump oopses, 0 to only dump panics (default 1)");
+		 "set to 1 to dump oopses, 0 to only dump panics (default 1), deprecated use max_reason instead");
+
+static int max_reason;
+module_param(max_reason, int, 0400);
+MODULE_PARM_DESC(max_reason,
+		 "maximum reason for kmsg dump. (default 2) ");
 
 static int ramoops_ecc;
 module_param_named(ecc, ramoops_ecc, int, 0600);
@@ -689,6 +694,7 @@ static int ramoops_parse_dt(struct platform_device *pdev,
 	parse_size("pmsg-size", pdata->pmsg_size);
 	parse_size("ecc-size", pdata->ecc_info.ecc_size);
 	parse_size("flags", pdata->flags);
+	parse_size("max_reason", pdata->max_reason);
 
 #undef parse_size
 
@@ -939,6 +945,7 @@ static void __init ramoops_register_dummy(void)
 	pdata.console_size = ramoops_console_size;
 	pdata.ftrace_size = ramoops_ftrace_size;
 	pdata.pmsg_size = ramoops_pmsg_size;
+	pdata.max_reason = max_reason;
 	pdata.flags = RAMOOPS_FLAG_FTRACE_PER_CPU;
 
 	/*
-- 
2.25.1