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

[NeilBrown <neilb@suse.de>]

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On Mon, 4 Jun 2012 13:36:11 +0800 majianpeng <majianpeng@gmail.com> wrote:

> On Sun, 3 Jun 2012 20:49:05 -0700,neil wrote:
> >On Thu, 31 May 2012 15:41:22 +0800 "majianpeng" <majianpeng@gmail.com> wrote:
> >
> >> When raid takeovered, it used old personality to set task->comm.
> >> 
> >> Signed-off-by: majianpeng <majianpeng@gmail.com>
> >> ---
> >>  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?

good point.

If you change all calls to "md_register_thread" that pass NULL as the last
argument to instead pass the name of the personality as the last arg,
then it should get it right.

Thanks,
NeilBrown


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