linux-block.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Bart Van Assche <bvanassche@acm.org>
To: Luis Chamberlain <mcgrof@kernel.org>,
	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
Cc: mhocko@suse.com, linux-block@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Omar Sandoval <osandov@fb.com>, Hannes Reinecke <hare@suse.com>,
	Michal Hocko <mhocko@kernel.org>
Subject: Re: [RFC 3/3] block: avoid deferral of blk_release_queue() work
Date: Wed, 1 Apr 2020 20:39:48 -0700	[thread overview]
Message-ID: <774a33e8-43ba-143f-f6fd-9cb0ae0862ac@acm.org> (raw)
In-Reply-To: <20200402000002.7442-4-mcgrof@kernel.org>

On 2020-04-01 17:00, Luis Chamberlain wrote:
> Commit dc9edc44de6c ("block: Fix a blk_exit_rl() regression") moved
> the blk_release_queue() into a workqueue after a splat floated around
> with some work here which could sleep in blk_exit_rl().
> 
> On recent commit db6d9952356 ("block: remove request_list code") though
> Jens Axboe removed this code, now merged since v5.0. We no longer have
> to defer this work.
> 
> By doing this we also avoid failing to detach / attach a block
> device with a BLKTRACESETUP. This issue can be reproduced with
> break-blktrace [0] using:
> 
>   break-blktrace -c 10 -d -s
> 
> The kernel does not crash without this commit, it just fails to
> create the block device because the prior block device removal
> deferred work is pending. After this commit we can use the above
> flaky use of blktrace without an issue.
> 
> [0] https://github.com/mcgrof/break-blktrace
> 
> Cc: Bart Van Assche <bvanassche@acm.org>
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Hannes Reinecke <hare@suse.com>
> Cc: Nicolai Stange <nstange@suse.de>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Michal Hocko <mhocko@kernel.org>
> Suggested-by: Nicolai Stange <nstange@suse.de>
> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
> ---
>  block/blk-sysfs.c | 18 +++++-------------
>  1 file changed, 5 insertions(+), 13 deletions(-)
> 
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index 20f20b0fa0b9..f159b40899ee 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -862,8 +862,8 @@ static void blk_exit_queue(struct request_queue *q)
>  
>  
>  /**
> - * __blk_release_queue - release a request queue
> - * @work: pointer to the release_work member of the request queue to be released
> + * blk_release_queue - release a request queue
> + * @kojb: pointer to the kobj representing the request queue
>   *
>   * Description:
>   *     This function is called when a block device is being unregistered. The
> @@ -873,9 +873,10 @@ static void blk_exit_queue(struct request_queue *q)
>   *     of the request queue reaches zero, blk_release_queue is called to release
>   *     all allocated resources of the request queue.
>   */
> -static void __blk_release_queue(struct work_struct *work)
> +static void blk_release_queue(struct kobject *kobj)
>  {
> -	struct request_queue *q = container_of(work, typeof(*q), release_work);
> +	struct request_queue *q =
> +		container_of(kobj, struct request_queue, kobj);
>  
>  	if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags))
>  		blk_stat_remove_callback(q, q->poll_cb);
> @@ -905,15 +906,6 @@ static void __blk_release_queue(struct work_struct *work)
>  	call_rcu(&q->rcu_head, blk_free_queue_rcu);
>  }
>  
> -static void blk_release_queue(struct kobject *kobj)
> -{
> -	struct request_queue *q =
> -		container_of(kobj, struct request_queue, kobj);
> -
> -	INIT_WORK(&q->release_work, __blk_release_queue);
> -	schedule_work(&q->release_work);
> -}
> -
>  static const struct sysfs_ops queue_sysfs_ops = {
>  	.show	= queue_attr_show,
>  	.store	= queue_attr_store,

The description of this patch mentions a single blk_release_queue() call
that happened in the past from a context from which sleeping is not
allowed and from which sleeping is allowed today. Have all other
blk_release_queue() / blk_put_queue() calls been verified to see whether
none of these happens from a context from which sleeping is not allowed?

Thanks,

Bart.



  reply	other threads:[~2020-04-02  3:39 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-01 23:59 [RFC 0/3] block: address blktrace use-after-free Luis Chamberlain
2020-04-02  0:00 ` [RFC 1/3] block: move main block debugfs initialization to its own file Luis Chamberlain
2020-04-05  3:12   ` Bart Van Assche
2020-04-06 14:23     ` Luis Chamberlain
2020-04-02  0:00 ` [RFC 2/3] blktrace: fix debugfs use after free Luis Chamberlain
2020-04-02  1:57   ` Eric Sandeen
2020-04-02 16:14     ` Luis Chamberlain
2020-04-05  3:39   ` Bart Van Assche
2020-04-06  1:27     ` Eric Sandeen
2020-04-06  4:25       ` Bart Van Assche
2020-04-06  9:18         ` Nicolai Stange
2020-04-06 15:19           ` Luis Chamberlain
2020-04-07  8:15             ` Luis Chamberlain
2020-04-06 14:29         ` Eric Sandeen
2020-04-07  8:09           ` Luis Chamberlain
2020-04-06 15:14     ` Luis Chamberlain
2020-04-02  0:00 ` [RFC 3/3] block: avoid deferral of blk_release_queue() work Luis Chamberlain
2020-04-02  3:39   ` Bart Van Assche [this message]
2020-04-02 14:49     ` Nicolai Stange
2020-04-06  9:11       ` Nicolai Stange
2020-04-09 18:11       ` Luis Chamberlain
2020-04-02  7:44 ` [RFC 0/3] block: address blktrace use-after-free Greg KH
2020-04-03  8:19 ` Ming Lei
2020-04-03 14:06   ` Luis Chamberlain
2020-04-03 14:13   ` Bart Van Assche
2020-04-03 19:49     ` Luis Chamberlain
2020-04-07  2:47   ` yukuai (C)
2020-04-07 19:00     ` Luis Chamberlain
2020-04-09 20:59       ` Luis Chamberlain

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=774a33e8-43ba-143f-f6fd-9cb0ae0862ac@acm.org \
    --to=bvanassche@acm.org \
    --cc=axboe@kernel.dk \
    --cc=gregkh@linuxfoundation.org \
    --cc=hare@suse.com \
    --cc=jack@suse.cz \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mcgrof@kernel.org \
    --cc=mhocko@kernel.org \
    --cc=mhocko@suse.com \
    --cc=ming.lei@redhat.com \
    --cc=mingo@redhat.com \
    --cc=nstange@suse.de \
    --cc=osandov@fb.com \
    --cc=rostedt@goodmis.org \
    --cc=viro@zeniv.linux.org.uk \
    --subject='Re: [RFC 3/3] block: avoid deferral of blk_release_queue() work' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox