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From: Luis Chamberlain <mcgrof@kernel.org>
To: Bart Van Assche <bvanassche@acm.org>
Cc: axboe@kernel.dk, viro@zeniv.linux.org.uk,
	gregkh@linuxfoundation.org, rostedt@goodmis.org,
	mingo@redhat.com, jack@suse.cz, ming.lei@redhat.com,
	nstange@suse.de, akpm@linux-foundation.org, mhocko@suse.com,
	yukuai3@huawei.com, linux-block@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 4/5] blktrace: break out of blktrace setup on concurrent calls
Date: Mon, 11 May 2020 13:39:00 +0000	[thread overview]
Message-ID: <20200511133900.GL11244@42.do-not-panic.com> (raw)
In-Reply-To: <e728acea-61c1-fcb5-489b-9be8cafe61ea@acm.org>

On Sat, May 09, 2020 at 06:09:38PM -0700, Bart Van Assche wrote:
> On 2020-05-08 20:10, Luis Chamberlain wrote:
> > @@ -493,6 +496,12 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
> >  	 */
> >  	strreplace(buts->name, '/', '_');
> >  
> > +	if (q->blk_trace) {
> > +		pr_warn("Concurrent blktraces are not allowed on %s\n",
> > +			buts->name);
> > +		return -EBUSY;
> > +	}
> > +
> >  	bt = kzalloc(sizeof(*bt), GFP_KERNEL);
> >  	if (!bt)
> >  		return -ENOMEM;
> 
> Is this really sufficient? Shouldn't concurrent do_blk_trace_setup()
> calls that refer to the same request queue be serialized to really
> prevent that debugfs attribute creation fails?

We'd have to add something like a linked list. Right now I'm just
clarifying things which were not clear before. What you describe is
a functional feature change. I'm just trying to fix a bug and clarify
limitations.

> How about using the block device name instead of the partition name in
> the error message since the concurrency context is the block device and
> not the partition?

blk device argument can be NULL here. sg-generic is one case.

 Luis

  reply	other threads:[~2020-05-11 13:39 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-09  3:10 [PATCH v4 0/5] block: fix blktrace debugfs use after free Luis Chamberlain
2020-05-09  3:10 ` [PATCH v4 1/5] block: revert back to synchronous request_queue removal Luis Chamberlain
2020-05-10  0:36   ` Bart Van Assche
2020-05-10  6:20   ` Greg KH
2020-05-11 13:41     ` Luis Chamberlain
2020-05-09  3:10 ` [PATCH v4 2/5] block: move main block debugfs initialization to its own file Luis Chamberlain
2020-05-09  3:10 ` [PATCH v4 3/5] blktrace: fix debugfs use after free Luis Chamberlain
2020-05-10  0:58   ` Bart Van Assche
2020-05-11 13:44     ` Luis Chamberlain
2020-05-10  6:26   ` Greg KH
2020-05-11 14:03     ` Luis Chamberlain
2020-05-09  3:10 ` [PATCH v4 4/5] blktrace: break out of blktrace setup on concurrent calls Luis Chamberlain
2020-05-10  1:09   ` Bart Van Assche
2020-05-11 13:39     ` Luis Chamberlain [this message]
2020-05-16  1:39       ` Luis Chamberlain
2020-05-16  1:39         ` Luis Chamberlain
2020-05-09  3:10 ` [PATCH v4 5/5] loop: be paranoid on exit and prevent new additions / removals Luis Chamberlain

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