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.
next prev parent 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
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