Re: blktrace hangs after "--kill" option

[Jens Axboe <jens.axboe@oracle.com>]

On Tue, Feb 03 2009, Vinay Sridhar wrote:
> Jens,
> 
> Any plans of including this in any of the 2.6.29 rc's?

It's already included in 2.6.29-git, it'll be in the next -rc.

> 
> Thanks,
> Vinay
> 
> On Mon, 2009-01-05 at 10:15 +0100, Jens Axboe wrote:
> > On Fri, Jan 02 2009, Vinay Sridhar wrote:
> > > Hello,
> > > 
> > > On executing "blktrace -k" on a running trace, the trace hangs. After
> > > killing the trace, rerunning it results in "BLKTRACESTOP: invalid
> > > argument" messages.
> > > 
> > > This was discussed earlier here:
> > > http://www.mail-archive.com/linux-btrace@vger.kernel.org/msg00229.html
> > > 
> > > But I dont see this fix to have been included as I'm still seeing this
> > > error with the the latest kernel. Could someone please indicate why this
> > > fix didnt go in? I was able to port the above suggested fix to 2.6.28.
> > 
> > I think I wanted to test it a bit more. I'll toss it in for 2.6.29 and
> > give it some testing! Thanks for the reminder...
> > 
> > 
> > > 
> > > 
> > > diff -Nuarp a/block/blktrace.c b/block/blktrace.c
> > > --- a/block/blktrace.c	2008-12-24 17:26:37.000000000 -0600
> > > +++ b/block/blktrace.c	2009-01-02 11:13:11.000000000 -0600
> > > @@ -181,59 +181,12 @@ EXPORT_SYMBOL_GPL(__blk_add_trace);
> > >  
> > >  static struct dentry *blk_tree_root;
> > >  static DEFINE_MUTEX(blk_tree_mutex);
> > > -static unsigned int root_users;
> > > -
> > > -static inline void blk_remove_root(void)
> > > -{
> > > -	if (blk_tree_root) {
> > > -		debugfs_remove(blk_tree_root);
> > > -		blk_tree_root = NULL;
> > > -	}
> > > -}
> > > -
> > > -static void blk_remove_tree(struct dentry *dir)
> > > -{
> > > -	mutex_lock(&blk_tree_mutex);
> > > -	debugfs_remove(dir);
> > > -	if (--root_users = 0)
> > > -		blk_remove_root();
> > > -	mutex_unlock(&blk_tree_mutex);
> > > -}
> > > -
> > > -static struct dentry *blk_create_tree(const char *blk_name)
> > > -{
> > > -	struct dentry *dir = NULL;
> > > -	int created = 0;
> > > -
> > > -	mutex_lock(&blk_tree_mutex);
> > > -
> > > -	if (!blk_tree_root) {
> > > -		blk_tree_root = debugfs_create_dir("block", NULL);
> > > -		if (!blk_tree_root)
> > > -			goto err;
> > > -		created = 1;
> > > -	}
> > > -
> > > -	dir = debugfs_create_dir(blk_name, blk_tree_root);
> > > -	if (dir)
> > > -		root_users++;
> > > -	else {
> > > -		/* Delete root only if we created it */
> > > -		if (created)
> > > -			blk_remove_root();
> > > -	}
> > > -
> > > -err:
> > > -	mutex_unlock(&blk_tree_mutex);
> > > -	return dir;
> > > -}
> > >  
> > >  static void blk_trace_cleanup(struct blk_trace *bt)
> > >  {
> > > -	relay_close(bt->rchan);
> > >  	debugfs_remove(bt->msg_file);
> > >  	debugfs_remove(bt->dropped_file);
> > > -	blk_remove_tree(bt->dir);
> > > +	relay_close(bt->rchan);
> > >  	free_percpu(bt->sequence);
> > >  	free_percpu(bt->msg_data);
> > >  	kfree(bt);
> > > @@ -336,7 +289,18 @@ static int blk_subbuf_start_callback(str
> > >  
> > >  static int blk_remove_buf_file_callback(struct dentry *dentry)
> > >  {
> > > +	struct dentry *parent = dentry->d_parent;
> > >  	debugfs_remove(dentry);
> > > +
> > > +	/*
> > > +	* this will fail for all but the last file, but that is ok. what we
> > > +	* care about is the top level buts->name directory going away, when
> > > +	* the last trace file is gone. Then we don't have to rmdir() that
> > > +	* manually on trace stop, so it nicely solves the issue with
> > > +	* force killing of running traces.
> > > +	*/
> > > +
> > > +	debugfs_remove(parent);
> > >  	return 0;
> > >  }
> > >  
> > > @@ -394,7 +358,15 @@ int do_blk_trace_setup(struct request_qu
> > >  		goto err;
> > >  
> > >  	ret = -ENOENT;
> > > -	dir = blk_create_tree(buts->name);
> > > +
> > > +	if (!blk_tree_root) {
> > > +		blk_tree_root = debugfs_create_dir("block", NULL);
> > > +		if (!blk_tree_root)
> > > +			return -ENOMEM;
> > > +	}
> > > +
> > > +	dir = debugfs_create_dir(buts->name, blk_tree_root);
> > > +
> > >  	if (!dir)
> > >  		goto err;
> > >  
> > > @@ -437,8 +409,6 @@ int do_blk_trace_setup(struct request_qu
> > >  
> > >  	return 0;
> > >  err:
> > > -	if (dir)
> > > -		blk_remove_tree(dir);
> > >  	if (bt) {
> > >  		if (bt->msg_file)
> > >  			debugfs_remove(bt->msg_file);
> > > 
> > > 
> > > 
> > > Vinay Sridhar,
> > > Linux Technology Center,
> > > IBM ISTL,
> > > Bangalore, India
> > > 
> > > 
> > 
> 

-- 
Jens Axboe