[PATCH net-next 5/7] netconsole: add task name to extra data fields

[Breno Leitao <leitao@debian.org>]

This is the core patch for this whole patchset. Add support for
including the current task's name in netconsole's extra data output.
This adds a new append_taskname() function that writes the task name
(from current->comm) into the target's extradata buffer, similar to how
CPU numbers are handled.

The task name is included when the SYSDATA_TASKNAME field is set,
appearing in the format "taskname=<name>" in the output. This additional
context can help with debugging by showing which task generated each
console message.

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 drivers/net/netconsole.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 5a29144ae37ee7b487b1a252b0f2ce8574f9cefa..625f4c0be11d8deb454139b1c526abc842697219 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -1179,12 +1179,22 @@ static int append_cpu_nr(struct netconsole_target *nt, int offset)
 			 raw_smp_processor_id());
 }
 
+static int append_taskname(struct netconsole_target *nt, int offset)
+{
+	if (WARN_ON_ONCE(!current))
+		return 0;
+
+	return scnprintf(&nt->extradata_complete[offset],
+			 MAX_EXTRADATA_ENTRY_LEN, " taskname=%s\n",
+			 current->comm);
+}
 /*
  * prepare_extradata - append sysdata at extradata_complete in runtime
  * @nt: target to send message to
  */
 static int prepare_extradata(struct netconsole_target *nt)
 {
+	u32 fields = SYSDATA_CPU_NR | SYSDATA_TASKNAME;
 	int extradata_len;
 
 	/* userdata was appended when configfs write helper was called
@@ -1192,11 +1202,13 @@ static int prepare_extradata(struct netconsole_target *nt)
 	 */
 	extradata_len = nt->userdata_length;
 
-	if (!(nt->sysdata_fields & SYSDATA_CPU_NR))
+	if (!(nt->sysdata_fields & fields))
 		goto out;
 
 	if (nt->sysdata_fields & SYSDATA_CPU_NR)
 		extradata_len += append_cpu_nr(nt, nt->userdata_length);
+	if (nt->sysdata_fields & SYSDATA_TASKNAME)
+		extradata_len += append_taskname(nt, extradata_len);
 
 	WARN_ON_ONCE(extradata_len >
 		     MAX_EXTRADATA_ENTRY_LEN * MAX_EXTRADATA_ITEMS);

-- 
2.43.5