Re: Re: [PATCH] md:Fix name of raid thread when raid takeovered

On Sun, 3 Jun 2012 20:49:05 -0700,neil wrote:

On Thu, 31 May 2012 15:41:22 +0800 "majianpeng" [off-list ref] wrote:

quoted

When raid takeovered, it used old personality to set task->comm.

Signed-off-by: majianpeng <redacted>
---
 drivers/md/md.c |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 1c2f904..93e20ea 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c

@@ -32,6 +32,7 @@
    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
+#include <linux/sched.h>
 #include <linux/kthread.h>
 #include <linux/blkdev.h>
 #include <linux/sysctl.h>

@@ -3513,6 +3514,7 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
 	long level;
 	void *priv;
 	struct md_rdev *rdev;
+	char *tmp;
 
 	if (mddev->pers == NULL) {
 		if (len == 0)

@@ -3674,6 +3676,19 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
 		del_timer_sync(&mddev->safemode_timer);
 	}
 	pers->run(mddev);
+	/*
+	 * when raid takeover using old personality,so mddev->thread->tsk
+	 * name is wrong.
+	 * if kzalloc error, only using wrong name.
+	 */
+	len = strlen(mdname(mddev)) + strlen(mddev->pers->name);
+	tmp = kzalloc(len + 2, GFP_KERNEL);
+	if (tmp) {
+		sprintf(tmp, "%s_%s", mdname(mddev), mddev->pers->name);
+		set_task_comm(mddev->thread->tsk, tmp);
+		kfree(tmp);
+	}
+
 	set_bit(MD_CHANGE_DEVS, &mddev->flags);
 	mddev_resume(mddev);
 	sysfs_notify(&mddev->kobj, NULL, "level");

Thanks.  However:

1/ as a task name is limited to TASK_COMM_LEN, there is little point using
   kzalloc.  Just declare a local variable of that size.
2/ No all levels have a thread.  You should check that mddev->thread is not
   NULL.

If you resubmit with those fixes I'll apply the patch.

Thanks,
NeilBrown

Neil, There maybe had anthor issue.
set_task_comm() is not export.So when compile md is module, it will be error.
So I think  it will be rewrite.It should rename in function call md_register_thread().
How about this way?
														Thanks!

--------------
majianpeng