On Tue 2020-05-05 11:45:06, Pavel Tatashin wrote:
> 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@xxxxxxxxxx>
> ---
> include/linux/kmsg_dump.h | 1 +
> kernel/printk/printk.c | 15 +++++++++++----
> 2 files changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
> index 2e7a1e032c71..cfc042066be7 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
> };
>
> /**
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 9a9b6156270b..1aab69a8a2bf 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -3157,12 +3157,19 @@ 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)
> + enum kmsg_dump_reason cur_reason = dumper->max_reason;
If this code is still in the next version, please, rename this variable
to max_reason or so.
"cur" is ambiguous. It might be current dumper or current message
which confused me later in the code ;-)
Best Regards,
Petr
> +
> + /*
> + * If client has not provided a specific max_reason, default
> + * to KMSG_DUMP_OOPS, unless always_kmsg_dump was set.
> + */
> + if (cur_reason == KMSG_DUMP_UNDEF) {
> + cur_reason = always_kmsg_dump ? KMSG_DUMP_MAX :
> + KMSG_DUMP_OOPS;
> + }
> + if (reason > cur_reason)
> continue;
>
> /* initialize iterator with data about the stored records */
> --
> 2.25.1
