From: Bart Van Assche <bvanassche@acm.org>
To: Ming Lei <ming.lei@redhat.com>
Cc: peterz@infradead.org, mingo@redhat.com, will.deacon@arm.com,
tj@kernel.org, longman@redhat.com, johannes.berg@intel.com,
linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
Theodore Ts'o <tytso@mit.edu>
Subject: Re: [PATCH v7 21/23] block: Avoid that flushing triggers a lockdep complaint
Date: Fri, 15 Feb 2019 08:08:08 -0800 [thread overview]
Message-ID: <1550246888.31902.97.camel@acm.org> (raw)
In-Reply-To: <20190215022658.GB21045@ming.t460p>
On Fri, 2019-02-15 at 10:26 +0800, Ming Lei wrote:
> There might be lots of blk_flush_queue instance which is allocated
> for each hctx, then lots of class key slot may be wasted.
>
> So I suggest to use one nvmet_loop_flush_lock_key for this particular issue,
> something like the following patch:
>
> diff --git a/drivers/nvme/target/loop.c b/drivers/nvme/target/loop.c
> index 4aac1b4a8112..ec4248c12ed9 100644
> --- a/drivers/nvme/target/loop.c
> +++ b/drivers/nvme/target/loop.c
> @@ -524,7 +524,9 @@ static const struct nvme_ctrl_ops nvme_loop_ctrl_ops = {
>
> static int nvme_loop_create_io_queues(struct nvme_loop_ctrl *ctrl)
> {
> - int ret;
> + static struct lock_class_key nvme_loop_flush_lock_key;
> + int ret, i;
> + struct blk_mq_hw_ctx *hctx;
>
> ret = nvme_loop_init_io_queues(ctrl);
> if (ret)
> @@ -553,6 +555,10 @@ static int nvme_loop_create_io_queues(struct nvme_loop_ctrl *ctrl)
> goto out_free_tagset;
> }
>
> + queue_for_each_hw_ctx(ctrl->ctrl.connect_q, hctx, i)
> + lockdep_set_class(&hctx->fq->mq_flush_lock,
> + &nvme_loop_flush_lock_key);
> +
> ret = nvme_loop_connect_io_queues(ctrl);
> if (ret)
> goto out_cleanup_connect_q;
Hi Ming,
Thanks for your feedback.
Are you aware that sizeof(struct lock_class_key) is zero if lockdep is
disabled? Does this alleviate your concern?
I'm not enthusiast about your patch. I don't think that block layer users
should touch the lock class key of the flush queue. That's a key that should
be set by the block layer core.
Anyway, let's drop patches 20/23 and 21/23 from this series and let's
continue this discussion on the linux-block mailing list after agreement has
been reached about the "dynamic lockdep key" approach.
Bart.
next prev parent reply other threads:[~2019-02-15 16:08 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-14 23:00 [PATCH v7 00/23] locking/lockdep: Add support for dynamic keys Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 01/23] locking/lockdep: Fix two 32-bit compiler warnings Bart Van Assche
2019-02-28 7:02 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 02/23] locking/lockdep: Fix reported required memory size (1/2) Bart Van Assche
2019-02-28 7:03 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 03/23] locking/lockdep: Fix reported required memory size (2/2) Bart Van Assche
2019-02-28 7:03 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 04/23] locking/lockdep: Avoid that add_chain_cache() adds an invalid chain to the cache Bart Van Assche
2019-02-28 7:04 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 05/23] locking/lockdep: Reorder struct lock_class members Bart Van Assche
2019-02-28 7:05 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 06/23] locking/lockdep: Make zap_class() remove all matching lock order entries Bart Van Assche
2019-02-28 7:05 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 07/23] locking/lockdep: Initialize the locks_before and locks_after lists earlier Bart Van Assche
2019-02-28 7:06 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 08/23] locking/lockdep: Split lockdep_free_key_range() and lockdep_reset_lock() Bart Van Assche
2019-02-28 7:07 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 09/23] locking/lockdep: Make it easy to detect whether or not inside a selftest Bart Van Assche
2019-02-28 7:07 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 10/23] locking/lockdep: Update two outdated comments Bart Van Assche
2019-02-28 7:08 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 11/23] locking/lockdep: Free lock classes that are no longer in use Bart Van Assche
2019-02-28 7:09 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 12/23] locking/lockdep: Reuse list entries " Bart Van Assche
2019-02-28 7:09 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 13/23] locking/lockdep: Introduce lockdep_next_lockchain() and lock_chain_count() Bart Van Assche
2019-02-28 7:10 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 14/23] locking/lockdep: Fix a comment in add_chain_cache() Bart Van Assche
2019-02-28 7:11 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 15/23] locking/lockdep: Reuse lock chains that have been freed Bart Van Assche
2019-02-28 7:11 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 16/23] locking/lockdep: Check data structure consistency Bart Van Assche
2019-02-28 7:12 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 17/23] locking/lockdep: Verify whether lock objects are small enough to be used as class keys Bart Van Assche
2019-02-28 7:13 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 18/23] locking/lockdep: Add support for dynamic keys Bart Van Assche
2019-02-26 17:17 ` Peter Zijlstra
2019-02-28 7:13 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 19/23] kernel/workqueue: Use dynamic lockdep keys for workqueues Bart Van Assche
2019-02-28 7:14 ` [tip:locking/core] " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 20/23] locking/spinlock: Introduce spin_lock_init_key() Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 21/23] block: Avoid that flushing triggers a lockdep complaint Bart Van Assche
2019-02-15 2:26 ` Ming Lei
2019-02-15 16:08 ` Bart Van Assche [this message]
2019-02-17 13:23 ` Ming Lei
2019-02-26 18:08 ` Peter Zijlstra
2019-02-27 1:35 ` Ming Lei
2019-02-27 14:24 ` Peter Zijlstra
2019-02-27 15:53 ` Ming Lei
2019-02-26 17:24 ` Peter Zijlstra
2019-02-26 17:48 ` Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 22/23] lockdep tests: Fix run_tests.sh Bart Van Assche
2019-02-28 7:15 ` [tip:locking/core] lockdep/lib/tests: " tip-bot for Bart Van Assche
2019-02-14 23:00 ` [PATCH v7 23/23] lockdep tests: Test dynamic key registration Bart Van Assche
2019-02-28 7:15 ` [tip:locking/core] lockdep/lib/tests: " tip-bot for Bart Van Assche
2019-02-21 22:02 ` [PATCH v7 00/23] locking/lockdep: Add support for dynamic keys Bart Van Assche
2019-02-22 16:26 ` Peter Zijlstra
2019-02-22 17:20 ` Bart Van Assche
2019-02-22 22:13 ` Peter Zijlstra
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=1550246888.31902.97.camel@acm.org \
--to=bvanassche@acm.org \
--cc=axboe@kernel.dk \
--cc=johannes.berg@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=longman@redhat.com \
--cc=ming.lei@redhat.com \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=tj@kernel.org \
--cc=tytso@mit.edu \
--cc=will.deacon@arm.com \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).