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Subject[PATCH v1 1/3] printk: honor the max_reason field in kmsg_dumper
Date
kmsg_dump() allows to dump kmesg buffer for various system events: oops,
panic, reboot, etc. It provides an interface to register a callback call
for clients, and in that callback interface there is a field "max_reason"
which gets ignored unless always_kmsg_dump is passed as kernel parameter.

Allow clients to decide max_reason, and keep the current behavior when
max_reason is not set.

Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
---
include/linux/kmsg_dump.h | 1 +
kernel/printk/printk.c | 16 +++++++++-------
2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
index 2e7a1e032c71..c0d703b7ce38 100644
--- a/include/linux/kmsg_dump.h
+++ b/include/linux/kmsg_dump.h
@@ -28,6 +28,7 @@ enum kmsg_dump_reason {
KMSG_DUMP_RESTART,
KMSG_DUMP_HALT,
KMSG_DUMP_POWEROFF,
+ KMSG_DUMP_MAX = KMSG_DUMP_POWEROFF
};

/**
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 9a9b6156270b..04c1e9a9b139 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3085,6 +3085,8 @@ EXPORT_SYMBOL(printk_timed_ratelimit);

static DEFINE_SPINLOCK(dump_list_lock);
static LIST_HEAD(dump_list);
+static bool always_kmsg_dump;
+module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);

/**
* kmsg_dump_register - register a kernel log dumper.
@@ -3106,6 +3108,12 @@ int kmsg_dump_register(struct kmsg_dumper *dumper)
spin_lock_irqsave(&dump_list_lock, flags);
/* Don't allow registering multiple times */
if (!dumper->registered) {
+ if (!dumper->max_reason) {
+ if (always_kmsg_dump)
+ dumper->max_reason = KMSG_DUMP_MAX;
+ else
+ dumper->max_reason = KMSG_DUMP_OOPS;
+ }
dumper->registered = 1;
list_add_tail_rcu(&dumper->list, &dump_list);
err = 0;
@@ -3141,9 +3149,6 @@ int kmsg_dump_unregister(struct kmsg_dumper *dumper)
}
EXPORT_SYMBOL_GPL(kmsg_dump_unregister);

-static bool always_kmsg_dump;
-module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
-
/**
* kmsg_dump - dump kernel log to kernel message dumpers.
* @reason: the reason (oops, panic etc) for dumping
@@ -3157,12 +3162,9 @@ void kmsg_dump(enum kmsg_dump_reason reason)
struct kmsg_dumper *dumper;
unsigned long flags;

- if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
- return;
-
rcu_read_lock();
list_for_each_entry_rcu(dumper, &dump_list, list) {
- if (dumper->max_reason && reason > dumper->max_reason)
+ if (reason > dumper->max_reason)
continue;

/* initialize iterator with data about the stored records */
--
2.25.1
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