From: Ming Lei <ming.lei@redhat.com>
To: Daniel Wagner <dwagner@suse.de>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
Jens Axboe <axboe@kernel.dk>, Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCH 2/2] block: hold queue lock while iterating in diskstats_show
Date: Thu, 20 Jan 2022 20:56:03 +0800 [thread overview]
Message-ID: <Yelb4+r5KuV67tO0@T590> (raw)
In-Reply-To: <20220120105248.117025-3-dwagner@suse.de>
On Thu, Jan 20, 2022 at 11:52:48AM +0100, Daniel Wagner wrote:
> The request queues can be freed while we operate on them. Make sure we
It shouldn't be freed here.
> hold a reference when using blk_mq_queue_tag_busy_iter.
>
> RIP: blk_mq_queue_tag_busy_iter
Any chance to pose the whole stack trace?
> Call Trace:
> ? blk_mq_hctx_mark_pending
> ? diskstats_show
> ? blk_mq_hctx_mark_pending
> blk_mq_in_flight
> diskstats_show
> ? klist_next
> seq_read
> proc_reg_read
> vfs_read
> ksys_read
> do_syscall_64
> entry_SYSCALL_64_after_hwframe
>
> Signed-off-by: Daniel Wagner <dwagner@suse.de>
> ---
> block/genhd.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/block/genhd.c b/block/genhd.c
> index c9d4386dd177..0e163055a4e6 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -1167,10 +1167,13 @@ static int diskstats_show(struct seq_file *seqf, void *v)
> if (bdev_is_partition(hd) && !bdev_nr_sectors(hd))
> continue;
> part_stat_read_all(hd, &stat);
> + if (blk_queue_enter(gp->queue, BLK_MQ_REQ_NOWAIT))
> + continue;
The disk device's refcnt is supposed to be grabbed by class device
iterator code, so queue shouldn't be released in diskstats_show().
Not mention blk_queue_enter() won't prevent disk from being released...
thanks,
Ming
next prev parent reply other threads:[~2022-01-20 12:56 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-20 10:52 [PATCH 0/2] fix crash by reading /proc/diskstats Daniel Wagner
2022-01-20 10:52 ` [PATCH 1/2] block: remove commented out code from diskstats_show Daniel Wagner
2022-01-20 11:02 ` Hannes Reinecke
2022-03-04 15:38 ` Daniel Wagner
2022-01-20 10:52 ` [PATCH 2/2] block: hold queue lock while iterating in diskstats_show Daniel Wagner
2022-01-20 11:18 ` Hannes Reinecke
2022-01-20 12:41 ` Daniel Wagner
2022-01-20 12:56 ` Ming Lei [this message]
2022-01-20 13:19 ` Daniel Wagner
2022-01-20 13:51 ` Ming Lei
2022-01-20 14:01 ` Daniel Wagner
2022-01-20 14:06 ` Daniel Wagner
2022-01-20 14:21 ` Christoph Hellwig
2022-01-20 14:34 ` Daniel Wagner
2022-01-20 15:37 ` Ming Lei
2022-01-20 16:29 ` Daniel Wagner
2022-03-04 14:53 ` Daniel Wagner
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